Документ взят из кэша поисковой машины. Адрес оригинального документа : http://www.stsci.edu/ftp/proposer/cycle8/Abstract-Catalog Дата изменения: Thu Dec 17 20:53:32 1998 Дата индексирования: Sat Dec 22 12:42:14 2007 Кодировка: Поисковые слова: earth's atmosphere

Cycle 8 Abstract Catalog (based on Phase I Submissions)
Generated on: Thu Dec 17 12:25:22 EST 1998

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Proposal Category: GO
Scientific Category: FIELD STELLAR POPULATIONS
ID: 8095
Title: Accurate proper motions of Galactic halo populations
PI: Rodrigo Ibata
PI Institution: European Southern Observatory

We propose to use the superb spatial resolution of the WFPC2 camera to
obtain second epoch exposures in the fields of several Galactic halo
globular clusters and dwarf satellite galaxies. The proper motions of these
populations will thereby be determined to unprecedented accuracy,
approximately an order of magnitude better than has been previously
possible. This will improve our understanding of the shape and distribution
of the dark matter halo of the Milky Way, it will allow better scrutiny of
formation models of the halo, it will allow us to investigate the dynamical
evolution of the Galactic satellites, and it will help constrain the
dynamics of foreground Galactic components. Stellar populations studies of
the Galactic halo objects can be (in some cases, substantially) improved,
since contaminants from foreground stellar populations and background
galaxian populations will be excluded from color-magnitude diagrams and
luminosity functions. Furthermore, we may also discover high redshift
supernovae.
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Proposal Category: GO
Scientific Category: INTERSTELLAR AND INTERGALACTIC MATTER
ID: 8096
Title: The interstellar medium near to and beyond the Galactic
Center
PI: Francis Keenan
PI Institution: Queen's University of Belfast

We have recently identified a B-type supergiant, LS 4825, which lies on the
far side of the Galaxy, at a Galactocentric distance of R_G = 12 kpc, and
whose sightline passes within 1 kpc of the Galactic Center. Optical ionCa2 and
ionNa1 interstellar observations of LS 4825 reveal a miriad of intermediate
and high velocity clouds, several of which arise from gas near to and beyond
the Galactic Center. We now propose to obtain medium resolution STIS spectra,
primarily to observe the ultraviolet interstellar lines towards LS 4825. These
data will allow us to determine the abundances of important elements such as
Mg, Si, S, Cr, Mn, Fe, and Zn (and possibly C, N, and O) in interstellar gas
as a function of Galactocentric distance, from the Solar position all the way
in to the Galactic Center and beyond, which is vital for testing the competing
models for the chemical evolution of our Galaxy. A secondary aim of the STIS
observations will be to study the ultraviolet stellar absorption lines in LS
4825, which will provide reliable element abundances for this star, and hence
the chemical composition of the interstellar medium at R_G = 12 kpc on the far
side of the Galaxy. This will be compared with results at R_G = 12 kpc on the
near side, to investigate the azimuthal dependence of the Galactic abundance
gradient.
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Proposal Category: GO
Scientific Category: INTERSTELLAR AND INTERGALACTIC MATTER
ID: 8097
Title: C IV High Velocity Clouds: Remnants of the Local Group?
PI: Kenneth Sembach
PI Institution: The Johns Hopkins University

We have recently studied two high velocity (V_LSR<-100 km s^-1) clouds (HVCs)
in the direction of Mrk 509 that have unusual ionization properties. The
clouds exhibit strong C IV absorption with little or no detectable low ion (C
II, Si II) absorption or H I 21cm emission. Our Cycle 6 program to study the
properties of the HVCs toward Mrk 509 in detail revealed that they are likely
very low density, low pressure gas clouds in the Local Group (or distant
Galactic halo) subject to the extragalactic ionizing background. Their
ionization properties resemble those of the outer diffuse halos of damped
LyAlpha absorbers and the low N(H I) metal line absorption systems seen in the
spectra of high redshift quasars. These ``C IV-HVCs'' present important
opportunities for relating the properties of nearby intergalactic gas (or an
extended Galactic halo) to the properties of gas in higher-z systems. Here,
we request STIS spectra to study the ionization properties of C IV-HVCs along
the PKS 2155-304 and PG 1116+215 sight lines. We will compare their properties
with those of the C IV-HVCs toward Mrk 509 to test the hypothesis that these
clouds are remnants from the formation of the Local Group. The results have
implications for the origin of HVCs, the processes that distribute and ionize
diffuse gas in the Local Group, the extent of the Galactic halo, and the
interpretation of high-z quasar absorption line systems.
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Proposal Category: GO
Scientific Category: AGN PHYSICS
ID: 8098
Title: Fe II emission lines as a chronometer for high-redshift
quasars
PI: Francis Keenan
PI Institution: Queen's University of Belfast

We request STIS observations of the symbiotic nova RR-TEL to give complete
coverage of ionFe2 emission lines in the 1150--9800 Angstrom\ wavelength
range. We have embarked on a long-term program to fully simulate the physical
conditions within ionFe2-emitting gas, and predict the resulting spectrum.
The first steps of generating the initial atomic database and incorporating
it into the photoionization code Cloudy, are complete. Analysis of the ionFe2
lines from RR-TEL using Cloudy will allow us to check the reliability and
completeness of the atomic data and processes considered, to investigate the
sensitivity of emission to temperature and density variations, and to assess
the importance of blending. Although emission lines from ionFe2 are observed
from a wide variety of astronomical objects, including protostellar disks,
novae, supernovae, and quasars, these lines have been notoriously difficult to
interpret because of the great complexity of the Fe^+ energy level structure.
We now have the tools to quantify the abundances in these objects and, once
calibrated against the RR-TEL data, we will apply the same technique to deduce
iron abundances from ionFe2 emission in high-redshift quasars. This, in
conjunction with predictions of stellar evolution and galactic
nucleosynthesis, will result in a chronometer measuring the redshift when the
universe passed through an age of 1 Gyr, thus constraining several
cosmological parameters.
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Proposal Category: GO
Scientific Category: STELLAR EJECTA
ID: 8099
Title: Imaging the Circumstellar Environments of the Cool
Hypergiants
PI: Roberta Humphreys
PI Institution: University of Minnesota

The cool hypergiants are evolved massive stars that lie just below the
empirical upper luminosity boundary in the HR Diagram, with spectral types
ranging from late A to M. Our recent observations of two of these stars have
yielded surprising results about their circumstellar environments including
evidence for bi-polarity, equatorial disks, and multiple high mass loss
events. To fully understand their mass loss histories, we need to sample these
stars at a variety of stages during their brief evolution as cool hypergiants.
We propose high resolution imaging of 8 of the most luminous known cool stars.
The presence or lack of fossil shells, equatorial ejecta, jets and other
structures in their circumstellar environments will be a record of their
current and prior mass loss episodes. Each star has been selected on the basis
of its infrared emission, strong molecular emission, or peculiar spectroscopic
variations to give us a snapshot of different steps in their evolution across
the top of the HR Diagram.
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Proposal Category: GO
Scientific Category: CLUSTERS, LENSING AND COSMOLOGY
ID: 8100
Title: Calibration of Nearby Type Ia Supernovae as Standard
Candles: The Next Step
PI: Abhijit Saha
PI Institution: National Optical Astronomy Observatories

We propose to continue our calibration experiment for M( max) of type Ia
supernovae (SNe Ia) by determining Cepheid distances to their parent galaxies.
To date we have completed (citeic4182a -- citengc4639) the calibration for 6
SNe Ia, from Cycles 1, and 3 -- 5. Our results from Cycle 6 on a seventh SN
Ia, SN 1989B in NGC 3627, are ready to be submitted citengc3627. Cepheid-
calibrated luminosities of two additional SNe Ia have become available from
external data. HST observations of NGC 4527 (SN 1991T) and a few test
exposures of NGC 1316 (SNe,1980N and 1981D) are planned for Cycle 7. Although
there are now a total of 9 SNe Ia with Cepheid-calibrated absolute magnitudes
M( max) in B and V, resulting values of H_0 in the literature range from 55
citeschaefer98 to 69 citeMKF98. The discrepancy depends on the exclusion of
some of the calibrators for various reasons, the inclusion of questionable
objects, and/or differences in second-parameter corrections. The only way out
of this dilemma is to obtain a statistically robust sample of SNe Ia with
reliable Cepheid distances. --- We request 2 * 34 orbits during Cycle 8 for
the discovery and two-passband photometry of the Cepheids in the two target
galaxies NGC 3982 (SN 1998aq) and NGC 1316 (SNe,1980N and 1981D), based on 2
orbits each for 12 epochs in F555W and 2 orbits each for 5 epochs in F814W.
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Proposal Category: GO
Scientific Category: GALAXY STRUCTURE AND DYNAMICS
ID: 8101
Title: High Resolution Imaging of the Core of Maffei 1, the
Nearest Normal Massive Elliptical Galaxy
PI: Ronald Buta
PI Institution: University of Alabama

We propose to obtain high resolution optical images of the center of the
galaxy Maffei 1, which is the nearest normal intermediate to giant elliptical
galaxy. Recent studies have shown that Maffei 1 is much larger (D_0 = 25^ )
and brighter (V_T^0 = 6.4) than previously thought, and that it is only 2.7 +/
- 0.6 Mpc distant. This is one-sixth the distance to the Virgo and Fornax
Cluster ellipticals, and 1 pixel in the Planetary Camera (PC) field covers
only 0.5--0.7 pc. Thus, with HST, we have the opportunity of studying the core
of a normal massive elliptical galaxy (M_V = -20.7) at sub-parsec spatial
resolution. Besides revealing the profile of light in the core, which is
invaluable for assessing the extent to which dissipation affected evolution,
our images will be used to search for evidence of a central concentration of
mass, including an accretion disk that might surround a supermassive black
hole. Because of the proximity of Maffei 1, we will be able to identify a
central black hole of considerably less mass
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Proposal Category: GO
Scientific Category: CS
ID: 8102
Title: FGS astrometry of the extrasolar planet of Gl 876
PI: Thierry Forveille
PI Institution: Observatoire de Grenoble

We propose astrometric observations with FGS1R in POS mode to confirm the
recent radial velocity detection of an extra-solar planet around the M4 dwarf
Gliese 876, by a totally independent method, and to determine the actual mass
of the planet without the unknown 1/sini factor of the radial velocity
methods. This will be the first extra-solar planet whose mass is actually
determined from first principles.
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Proposal Category: GO
Scientific Category: BINARY STARS
ID: 8103
Title: A Global Picture of White Dwarfs in Cataclysmic Variables
PI: Paula Szkody
PI Institution: University of Washington

During the past 6 yrs, we have demonstrated that UV spectra of 4 unique non-
magnetic Cataclysmic Variables in quiescence provide accurate temperatures,
rotation rates, chemical abundances of the photosphere and Einstein redshift
masses of the accreting white dwarfs in these systems. We are now in a
position to advance to a broader and deeper understanding of fundamental
tangential accretion physics and a global understanding of the accreting white
dwarf as a function of its evolutionary history by extending our analyses to
16 systems that are carefully selected to ensure detection of their underlying
white dwarfs. Applying the STIS spectral advantages of high sensitivity and
resolution to this large sample, we can refine the distribution of
temperatures, rotational velocities and composition as a function of orbital
period and system type, and determine the correlation of accretion belts with
missing or weak boundary layers and anamolous compositions. The physical
insights from these simplest and most observable systems should apply in the
broader context of equatorial accretion flows onto central compact objects in
a variety of disk accreting systems (T Tauri stars, X-ray binaries, disk
accreting symbiotics, Algols with transient disks).
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Proposal Category: GO
Scientific Category: AGN PHYSICS
ID: 8104
Title: Constraints on the Evolution of Powerful Radio Galaxies
PI: Christopher O'Dea
PI Institution: Space Telescope Science Institute

Recent work has identified the GHz Peaked Spectrum (GPS) and Compact Steep
Spectrum (CSS) radio sources as the most likely candidates for the
progenitors of the large scale powerful classical double (3CR FR2) sources.
WFPC2 LRF images have revealed the presence of bright emission line gas
aligned with and in projection co-spatial with the radio source. Ground based
observations of broad and highly structured OIIILambda 5007 lines strongly
suggest that the radio source is dominating the emission line kinematics. We
propose to observe 3 CSS sources with STIS long-slit spectroscopy in order to
determine the kinematics and physical properties of the emission line gas
interacting with the radio source. We will use diagnostic line ratios to
estimate the temperature and density of the gas. From the velocity field, we
will derive constraints on the expansion velocity of the radio source and on
the radio source lifetime, both of which are fundamental parameters needed to
constrain the evolution of powerful radio sources.
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Proposal Category: GO
Scientific Category: SOLAR SYSTEM
ID: 8105
Title: Global Change on Pluto?
PI: James Elliot
PI Institution: Massachusetts Institute of Technology

Pluto and Triton, two bodies that likely formed in the solar nebula (rather
than a pre-planetary nebula), hold the promise of telling us much about early
conditions in the outer solar system. Pluto and Triton are remarkably similar
in size and density, and each suffered an early catastrophic event: Triton's
retrograde orbit indicates that it was captured by Neptune, while Pluto's
binding with Charon also required a large dissipation of energy. The low
probability of such events for two isolated bodies implies that Pluto and
Triton have remained from a much larger Kuiper belt population that existed in
the past. Observation of a stellar occultation by last year with the FGS has
shown that (i) Triton has been undergoing a period of global warming, and (ii)
Triton has a much deeper troposphere than previously thought. A similar
observation of an occultation by Pluto is proposed to probe whether it is
undergoing global change as well. In addition to observing the occultation,
we propose astrometric observations that will be critical for deploying
portable telescopes and for interpreting Earth-based occultation observations,
even if the HST proves not to be within the occultation path.
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Proposal Category: GO
Scientific Category: GALAXY STRUCTURE AND DYNAMICS
ID: 8106
Title: The mass of the black hole in Cygnus A
PI: Clive Tadhunter
PI Institution: University of Sheffield,

Although supermassive black holes are thought to be the main power source for
the jets and active components of radio galaxies, the relationship between the
masses of the black holes, the bulges of the host galaxies, and the radio
activity are not understood with any certainty. Part of the problem has been
the lack of suitable dynamical tracers in the nuclei of the radio source host
galaxies. However, using HST imaging observations we have recently detected a
high surface brightness disk structure at the centre of the archetypal
powerful radio galaxy Cygnus A. We now propose to use STIS measurements of the
emission line kinematics in the disk to measure the mass of the core of the
galaxy, and thereby test the idea that powerful radio sources are only
associated with the most massive black holes (M_bh > 10^9 M_\odot) in the host
galaxies with the most massive galaxy bulges. Requiring only 5 orbits of HST
time, this project is fundamental to our general understanding of the energy
generation mechanisms in powerful radio galaxies. These observations will
represent the first attempt to map the kinematics of the ionized gas in detail
on a sub-kpc scale in a powerful FRII radio galaxy. Given the requirement for
high spatial resolution long-slit spectroscopy across the core of the galaxy,
this project can only be done with STIS on the HST.
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Proposal Category: GO
Scientific Category: CLUSTERS, LENSING AND COSMOLOGY
ID: 8107
Title: What is the Nature of the Cold Medium in Cooling Flow
Clusters? Clues from <~
PI: Christopher O'Dea
PI Institution: Space Telescope Science Institute

X-ray spectra of a significant fraction of cooling flow (CF) clusters of
galaxies indicate the presence of large columns of ``cold'' absorbing
material. The physical nature of the absorbing medium remains a mystery.
Searches for H I in this medium using the 21 cm hyperfine structure line, and
for molecular gas traced by CO yielded null results at the required levels.
The LyAlpha absorption cross section is >= 10^7 times larger than for the 21
cm line, and it can therefore be used as a much more sensitive probe of H I in
clusters. This method was applied to the Perseus CF cluster using a medium
resolution (~ 250 km s^-1) HST spectrum, yielding an upper limit on the H I
column about three orders of magnitude smaller than implied by X-ray spectra.
We propose to obtain higher resolution (~ 40 km s^-1), spatially extended
spectra of the Ly-alpha\ emission line filaments in three CF clusters with
the brightest known LyAlpha fluxes. These spectra will allow us to probe H I
columns about 10^7 smaller than deduced from the excess X-ray absorption in
these clusters (>= 10^20 cm^-2), and thus put very strong constraints on the
nature of the cold absorbing medium and its covering factor. If substantial
amounts of cold gas do exist in the ICM, this would have important
implications for our understanding of cooling flows, the physics of the ICM,
galaxy formation and evolution, and LyAlpha forest systems.
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Proposal Category: GO
Scientific Category: SOLAR SYSTEM
ID: 8108
Title: Search for Origin of Supersonic Turbulence Observed in
the Upper Equatorial Atmosphere of Jupiter
PI: Claude Emerich
PI Institution: CNRS-Institut d'Astrophysique Spatiale

It is now clear that Jupiter, like the Sun, sustains a coronal region at the
top of its atmosphere. H-Ly-alpha\ spectra measured by GHRS in the Jovian Ly-
alpha\ bulge region, evidenced a non thermal line broadening, implying
supersonic atomic motions and variability on a time scale of about one minute.
Such an atmospheric turbulence was suggested by Ben Jaffel et al. 1993 to
explain the Jovian Ly-alpha\ bulge by an enhancement of the H-Ly-alpha\
resonance cross-section rather than by a local increase of the H density.
Sommeria et al. 1995 proposed then a model of thermospheric circulation
reproducing the main characteristics of the bulge and explaining the heating
excess observed in the Jovian upper atmosphere. This temperature excess was
also explained by Yelle (1996) invoking heating from gravitational waves
dissipation. To put new constraints on these models, and to find out
potential alternative explanations, we propose to use STIS to make high-
resolution H-Ly-alpha\ line profile maps in four crucial regions of the
planet. Recent cycle 7 STIS auroral observations of J. Clarke et al.,
demonstrated its capability to provide a wealth of new information on spatial,
spectral and scale height distributions, allowing to refine our understanding
of the physical processes that drive this highly perturbed region of the
Jovian atmosphere, using only a few HST orbits.
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Proposal Category: GO
Scientific Category: AGN PHYSICS
ID: 8109
Title: Determination of the SED for TON S180: A Direct Probe of
the Big Blue Bump
PI: Jane Turner
PI Institution: Goddard Space Flight Center

The Seyfert 1 galaxy, TON S180, is the brightest AGN in the extreme UV regime,
there is a low Galactic column along the line-of-sight and no evidence for
intrinsic absorption. This offers a rare opportunity to obtain the spectral-
energy-distribution (SED) of the source, including data from the vital soft X-
ray to UV range which is generally difficult to observe due to absorption of
those photons by Galactic material. TON S180 has a strong soft X-ray excess,
and may be the best case in which to confirm the presence of a Big Blue Bump
(BBB). The existence of a BBB in the EUV continuum is extremely
controversial. For example, although the SEDs derived from QSO spectra appear
to be power-laws, photoionization models based on these fits greatly
underpredict the strength of the He II emission lines. This apparent deficit
of He II ionizing photons could be explained if a BBB were indeed present. We
request a STIS observation of TON S180, to be made simultaneous with our
approved AXAF and FUSE observations. The combined data will allow us to
determine the SED and test the presence of a BBB, addressing the photon
deficit problem in detail.
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Proposal Category: GO
Scientific Category: STELLAR EJECTA
ID: 8110
Title: Supernova Remnants in a Cloudy Interstellar Medium
PI: You-Hua Chu
PI Institution: University of Illinois

Small cloudlets in the interstellar medium (ISM) may have a marked effect on
the physical structure and evolution of supernova remnants (SNRs). The
effects of evaporating cloudlets in a SNR interior have been modeled and are
an important factor leading to McKee & Ostriker's three-phase model of the
ISM. The cloudlets themselves are only now becoming observable through high-
resolution instruments such as the Hubble Space Telescope's Wide Field and
Planetary Camera (WFPC2). We propose WFPC2 observations of the three SNRs,
N49, N206, and N63A, which appear to be the best candidates for the
examination of the physical structure of SNRs in a cloudy ISM. These WFPC2
images can be combined with complementary observations in other wavelength
regimes to identify cloudlets inside remnants; trace SNR shock fronts;
determine the physical parameters of interior cloudlets and compare them to
those of the hot interior; and investigate the evaporation of shocked
cloudlets into the hot cavities of the SNRs.
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Proposal Category: GO
Scientific Category: CS
ID: 8111
Title: CS 22892--052: A Rosetta Star for the Age and Early
History of the Galaxy
PI: Christopher Sneden
PI Institution: University of Texas

We propose to observe the ultra-metal-poor Galactic halo star CS 22892--052
and to produce the most complete abundance distribution of the heaviest stable
elements, including platinum, osmium and lead, of any star outside of the Sun.
These HST abundance data will then be used to estimate the initial abundance
of the long-lived radioactive element thorium and, in comparison with its
observed abundance, will be used to determine the age of this very old star.
These studies, using radioactive chronometers in stars, provide an age
estimate for the Galaxy independent of globular cluster and cosmological ages.
Our proposed observations of CS 22892--052 will also provide significant new
information about the early history of the Galaxy, specifically the nature of
the earliest generations of stars and the types of nucleosynthetic processes
that occurred in those stars.
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Proposal Category: GO
Scientific Category: INTERSTELLAR AND INTERGALACTIC MATTER
ID: 8112
Title: Probing the Galactic Halo and Beyond with Young
Supernovae
PI: George Sonneborn
PI Institution: NASA/Goddard Space Flight Center

We propose a Target of Opportunity program to obtain STIS echelle spectra of a
bright new supernova (V<14) to characterize the ionization state, gas-phase
abundances, depletion on dust grains, metallicity, and gas kinematics in the
Galactic halo, the ISM and halo of the SN's host galaxy, and, if the
properties of the sightline are favorable, in the intervening intergalactic
medium. The principal spectral region for this study is the far ultraviolet
(\wl <1700Angstrom), which provides a comprehensive set of lines to study the
hot, warm, and cool phases of the ISM. Near-UV spectra will provide Zn II and
Cr II line profiles with which to assess gas-phase depletion. New core-
collapse supernovae, with their strong, nearly featureless UV continua,
provide outstanding opportunities to obtain high-quality absorption line
spectra of the gas on the line of sight to the SN, but only if the
observations are executed within ~2 weeks of outburst. Our team has the
experience and extensive ground-based support to rapidly assess the
suitability of each newly-discovered supernova for this program and provide
all the necessary data to efficiently implement the proposed observations, as
demonstrated by our successful low resolution observations of SN 1998S in
Cycle 7.
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Proposal Category: SNAP
Scientific Category: GALAXY POPULATIONS AND INTERACTIONS
ID: 8113
Title: Dust and Ultraviolet Light in the Local Universe
PI: Marie Treyer
PI Institution: Astrophysikalisches Institut Potsdam

Ground-based spectroscopy of a flux-limited sample of galaxies imaged at 2000
Angstrom\ with the FOCA balloon-borne camera has allowed us to derive a new
estimate of the local star formation rate (SFR) in a manner directly
comparable to that utilised for high redshift galaxies (Treyer et al. 1998).
Although UV radiation is a more sensitive tracer of instantaneous star
formation than optical light, the inferred SFR is significantly more sensitive
to unknown effects of dust scattering and absorption. Even modest dust
corrections would imply the strong evolution claimed in the 0 formation history has been grossly overestimated. We propose to address this
important possibility by estimating the amount of dust and its spatial
distribution in a random subset of our UV-selected galaxies. We will employ
Meurer et al. (1997)'s technique, which estimates the dust content of a star
forming galaxy from the observed UV spectral slope. The necessary wavelength
baseline will be provided by using STIS in snapshot imaging mode with both the
F25SRF2 (Lambda ~ 1480Angstrom) and F25QTZ filters (Lambda ~ 2320Angstrom). An
important bonus of STIS' high resolution images will be a measure of the
distribution of dust and star formation in a representative sample, including
a puzzling subset with anomalously strong UV continua.
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Proposal Category: GO
Scientific Category: INTERSTELLAR AND INTERGALACTIC MATTER
ID: 8114
Title: Fundamental Problems in Plasma Astrophysics: The Thermal
Equilibrium of NGC 7009
PI: Robert Rubin
PI Institution: NASA Ames Research Center

NGC 7009 has become the standard-bearer for a growing body of work that finds
nebular abundances derived from recombination lines are up to factors of 5--15
larger than those obtained from the optical/UV collisionally excited lines.
These can be forced into agreement at the higher value if large unexplained
temperature fluctuations (t^2) exist. STIS long-slit observations will allow
us to study the line-of-sight t^2 in addition to plane-of-the-sky variations,
within the slit areas, thereby creating 3-dimensional t^2 information. Using a
method we developed and recently applied to our Orion Nebula HST data, we will
find t^2 in the O^++ and N^+ regions using the highly T_e-sensitive ionO3 1663
and ionN2 2142 lines; this provides information on how t^2 depends on level
of ionization or excitation of the gas. We propose to complement the long-slit
STIS spectra with WFPC2 images in several filters, most importantly in the
4364 Angstrom\ and 5008 Angstrom\ lines of ionO3, whose ratio can be used to
diagnose T_e-fluctuations over the whole nebula on the microscopic scale
(0.1''). We have ISO IR spectroscopy of NGC 7009 to help further characterize
electron densities and T_e macroscopically. Our goals are to understand the
conditions within the nebula and the physical origin of the inferred t^2 and
to find a prescription for determining reliable nebular abundances --
fundamental to understanding the chemical evolution of the Galaxy.
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Proposal Category: GO
Scientific Category: CS
ID: 8115
Title: Stellar Seismology from Space: From the Sun to the Stars
PI: Jeff Valenti
PI Institution: National Optical Astronomy Observatories

We will use STIS to obtain the first unambigous detection of acoustic
oscillations in a solar-type star other than the Sun. Numerous ground-based
asteroseismology experiments have failed to produce a definitive signal partly
because scintillation in the Earth's atmosphere limits photometric precision.
From its vantage point in space, HST can reliably measure mode frequencies and
dominant splittings with an accuracy of 3 MuHz in only 15 CVZ orbits. We will
monitor brightness variations in a sequence of 3000+ exposures over a 24 hour
period. Using the G430L grating to disperse the light over 2000 CCD pixels, a
precision of 10^-4 will be achieved in each 5+20 second exposure. Detailed
Monte Carlo simulations based on full-disk solar observations indicate that we
will detect (>99\ about a dozen distinct frequencies (0<=\ell<=2). These
frequency measurements will enable us to determine stellar mass, age, and
helium abundance, while refining existing measurements of other parameters.
Hipparcos parallaxes coupled with a detailed spectroscopic analysis will
overconstrain stellar models, allowing a test of the underlying physics (the
onset of core convection, for example). This study will herald a new era of
practical asteroseismology, and serve as a benchmark for future space missions
dedicated to stellar seismology.
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Proposal Category: GO
Scientific Category: STELLAR EJECTA
ID: 8116
Title: Spectroscopy of the Rapidly-Evolving, Chemically
Inhomogeneous Planetary Nebula BD+30 3639
PI: J. Patrick Harrington
PI Institution: University of Maryland

BD +30^degrees3639 is one of the most important and extensively observed of
all planetary nebulae. One of the few PNe with X-ray emission from the shocked
stellar wind, it is an approved AXAF target. ISO observations led to the
unexpected discovery of crystalline silicates in this carbon-rich nebula.
This, and other evidence, shows that BD+30 has undergone rapid chemical
evolution, and is likely to show abundance anomalies and gradients in the
ionized gas. We propose to obtain several long-slit near-UV and optical
spectra of BD+30. This will enable us to map the C/O ratio with high spatial
resolution (~ 0.2"). We will also obtain co-spatial determinations of the
temperature and density, map the behavior of the enigmatic C II 4267
recombination line, and perhaps track the Si/C ratio. We propose 2nd-epoch
observations to our earlier (1994) WFPC2 images to measure the angular
expansion. To map the velocity field of BD+30 -- crucial to get its distance
from the angular expansion -- we will take echelle spectra in the C II
Lambda2326 line. Such detailed mapping is necessary in light of the discovery
of high-velocity outflows, not only in molecular gas (CO, H_2), but even
optical lines. These observations will complete a comprehensive picture of a
PN which can open a window onto the final dredge-up and mass-loss phase of AGB
evolution.
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Proposal Category: GO
Scientific Category: SOLAR SYSTEM
ID: 8117
Title: Saturn's FarUV Aurora and Polar Hazes
PI: John Trauger
PI Institution: Jet Propulsion Laboratory

We propose to carry out a coordinated program of STIS imaging and spectroscopy
in the FUV and NUV during one full rotation of the planet in order to capture
a complete picture of the south auroral emission region on Saturn. FUV
imaging and chapman-profile modeling is our lever to characterize emissions
from above the homopause, while FUV and NUV spectroscopy and radiative
transfer modeling will describe the atmospheric phenomena driven by particle
radiation that penetrates below the homopause. The proposed observation is a
direct extension of a program of WFPC2 and STIS imaging begun in Cycles 6 and
7. Very little is presently known about the range of possible morphologies
and temporal behaviors in the Saturn aurora. One complete rotation is
required to sort out the planet-fixed and local-time-fixed characteristics,
and to provide spectra with sufficient S/N to reliably constrain the radiative
transfer modeling.
================================================================================
Proposal Category: SNAP
Scientific Category: STELLAR POPULATIONS IN CLUSTERS
ID: 8118
Title: A Snapshot Survey of Galactic Globular Clusters
PI: Giampaolo Piotto
PI Institution: Universita di Padova

HST observations of crowded centers of globular clusters (GCs) have produced
intriguing discoveries of new phenomena, most of which are not understood
theoretically. We propose here a continuation of a Cycle 7 snapshot proposal,
to extend such work to a much larger portion of the Galactic GC system. Up to
now <20\ observed, with results that have been so fruitful that we propose to
complete the original target list, continuing to observe the centers in B and
V with WPFC2. We request a proprietary period of only 3 months. Our color-
magnitude diagrams will include all stars down to ~ 1^ m below the main-
sequence turnoff, allowing us to address many outstanding questions, such as:
How does the frequency of confirmed or suspected stellar interaction products
e.g., blue stragglers, horizontal branch (HB) tails depend upon the local
stellar density and the cluster dynamical state? How common are the strange HB
morphologies recently discovered by HST in several GCs, and are they confined
to the central regions? How often do metal-rich GCs have a hot HB, and does
it correlate with the cluster dynamics? We will also improve the core
parameters for a number of GCs, and constrain their dynamical states. This
survey will produce a fundamental data set of Galactic GCs, which will be
useful for a large number of studies in the years to come, and be a part of
the legacy of HST.
================================================================================
Proposal Category: GO
Scientific Category: GALAXY STRUCTURE AND DYNAMICS
ID: 8119
Title: Measuring the black hole mass in Centaurus A, the nearest
active galaxy
PI: Ethan J. Schreier
PI Institution: Space Telescope Science Institute

We will use STIS to measure the mass of the black hole at the center of
NGC5128 (Cen A), the nearest active galaxy. The presence of a super-massive
black hole, comparable to that of M87, is suggested by the jet, the extent of
the radio lobes, and the presence of strong nuclear radiation extending to
hard X-rays and Gamma-rays. A 1" (~ 17pc) radius ionized accretion disk at the
nucleus of Cen A was discovered in PaAlpha using HST NICMOS (Schreier et al.
1998); we have now (1998 August) also seen the disk in Fe IILambda1.643Mu m.
Recent near-IR ground based spectra (Blum, 1998 private communication) reveal
broadened lines near the nucleus, consistent with a central mass ~eq 10^9
M_\odot. These and other observations demonstrate that notwithstanding the
high dust extinction at the center of NGC5128, a number of lines in the ~eq0.9
-2.2Mu m range can be used to study the mass distribution. HST's spatial
resolution is required to yield a good mass determination. S IIILambda
9532Angstrom\ is the shortest wavelength line which is seen to be present and
is readily accessible to STIS. Observing with the G750L low-dispersion grating
of STIS through the 0arcs1 wide slit, we will thus use the S III emission line
as a gas tracer to measure the rotation curve of the disk, measure the mass
distribution in the central few parsecs of the galaxy, and determine the mass
of the black hole.
================================================================================
Proposal Category: GO
Scientific Category: YOUNG STARS AND CIRCUMSTELLAR MATERIAL
ID: 8120
Title: Determination of Circumstellar Cloud Mass Loss Rates with
STIS Spectra
PI: C. R. O'Dell
PI Institution: Rice University

We propose to resolve the question of whether or not the circumstellar disks
around young low mass stars in clusters containing O type stars are rapidly
destroyed by photoevaporation. The answer will determine whether or not the
conditions necessary for planet formation are common or rare in the massive
star clusters where most stars are created. At the present there is a
conundrum arising from the fact that most of the circumstellar disks survive
in the Orion Nebula Cluster even though the theoretical models predict that
the intense radiation field should have destroyed them in times short compared
with the estimated age of the cluster. We propose to obtain STIS high
resolution spectra which will allow direct measurement of any photoevaporative
flow off disks around two young low mass stars near \tc\ Ori. These results
will test existing theories for photoevaporation and directly tell us how long
these disks can survive. Only the HST and STIS have the right combination of
spatial and spectral resolution to adequately reject the contaminating light
from the Orion Nebula itself and allow clear determination of the emission
coming from the young stellar object.
================================================================================
Proposal Category: GO
Scientific Category: STELLAR EJECTA
ID: 8121
Title: Proper Motions and Variability of HH Objects Near the
Orion Nebula
PI: C. R. O'Dell
PI Institution: Rice University

The Orion nebula possesses at least three systems of HH objects, each with
very different characteristics. No other source shows such a variety of
outflow phenomena, and we seek to understand why this is so. An essential
parameter in understanding these systems and the individual shocks is their
spatial motions. A recent groundbased Fabry-Perot study has provided radial
velocities for all of the brightest members, but proper motion information is
uncertain and available for only a few. The existence of earlier WFPC2 images
presents an opportunity to produce accurate proper motions through repeating
those observations in Cycle 8. The proposed observations will clarify how
shocks sweep up material in the dense H II and Photodissociation Regions, and
pinpoint locations of photometric variability within the shocked cooling
zones. The timing for this is optimal since the sample of current proper
motions indicates that the 4.7-6.0 year time interval will allow accurate
results; the results should be obvious and unambiguous. By rotating the
field for one of the pointings we'll be able to obtain the first HST images in
O I and S II in one of the richest regions of the nebula. The product of this
investigation will be proper motions and temporal variability for all of the
HH objects in the region, and an O I and S II survey of an unstudied region.
================================================================================
Proposal Category: GO
Scientific Category: FIELD STELLAR POPULATIONS
ID: 8122
Title: The evolution of galaxies -- mining the stellar content
of the two most local Blue Compact Dwarf Galaxies
PI: Regina Schulte-Ladbeck
PI Institution: University of Pittsburgh

We propose to exploit the unique, high spatial resolution of the WFPC2 to
obtain deep color-magnitude diagrams (CMDs) of two newly recognized very
nearby (D<3 Mpc) blue compact dwarf galaxies (BCDs). The CMDs will be modeled
to extract the star-formation histories; in particular, we will use red-giant
stars to determine WHEN these galaxies first started to make the bulk of
their stellar population. This will provide an important alternative to
galaxy counts for testing the predictions of dwarf galaxy evolution. BCDs are
very small, nearby, starbursting systems which (at least in some cases) also
contain an older stellar population. The star-formation history of BCDs is a
key to understanding the enigmatic evolution of dwarf galaxy populations --
for example, the faint blue excess, thought to be due to low-mass galaxies
experiencing a short epoch of star formation at redshifts 0.5 the most important processes driving counts at very faint magnitudes are 1)
the delayed formation of dwarfs, where the collapse time-scales of the
interstellar gas is governed by photoionization by the metagalactic UV
background; and 2) the ensuing superwinds, which could allow loose gas to
escape these low-mass systems. Besides being candidates for the remnants of
the faint blue excess, BCDs provide a unique laboratory for understanding the
effects of starburst feedback on the interstellar meduim.
================================================================================
Proposal Category: GO
Scientific Category: GALAXY STRUCTURE AND DYNAMICS
ID: 8123
Title: Testing the Stellar Dynamics of Nested Bars in NGC 5728
PI: Isaac Shlosman
PI Institution: University of Kentucky

NIR images of the barred galaxy NGC 5728 revealed the existence of an inner
bar, twisted by a large angle, sim63^degrees relative to the primary bar.
Similar bars within bars have been found in nearby galaxies, their existence
in large numbers is of interest to understanding of barred galaxy dynamics and
of the fueling of nuclear starbursts and AGNs. Three theoretical schemes were
developed to explain this phenomena. Two require the gas self-gravity to
stabilize the inner bar and have it rotating in the same direction as the
primary bar at the same pattern speed or decoupled, so it rotates faster. The
third supposes that the inner bar is decoupled but counter rotates relative
to the primary, and alleviates the need for large gas masses required by the
former models. The predicted rotational properties and velocity dispersion
radial profiles of inner bars are radically different in all three cases and
can be tested using longslit absorption-line spectroscopy. As yet no
meaningful confrontation between the models and real galaxies was carried out,
as inner bars are confined to small physical (1 kpc) and angular scales (5-
7^'') and can only be well resolved with HST. We propose to acquire
absorption-line spectra along the inner bar of NGC 5728 with STIS and the
G750M grating at the Calcium triplet (Lambda 8498,8542,8662) to study its
stellar dynamics. Our results will be significant in understanding host galaxy
-to-central activity connection.
================================================================================
Proposal Category: GO
Scientific Category: STELLAR POPULATIONS IN CLUSTERS
ID: 8124
Title: The Stellar Initial Mass Function of Globular Clusters
PI: Giampaolo Piotto
PI Institution: Universita di Padova

Knowledge of star formation in old populations is a vital ingredient in
understanding galactic evolution. Globular star clusters offer the
possibility of observing the mass functions of homogeneous old stellar
populations. Those for which reliable mass functions have been determined
already, however, have generally been subject to dynamical evolution
(relaxation, escape of stars, and tidal shocks), so that the observed mass
function is not primordial. We have therefore examined tables of properties
of globular clusters in order to choose those that are least likely to have
suffered from relaxation, escape, and tidal shocks. We propose three new
targets (NGC 2808, M53, and M2), and dynamical rediscussion of existing data
on one other (M3). To minimize mass-segregation corrections, in each cluster
we will select a field at the radius where the local mass function most
closely resembles the global mass function. The range of metallicities of the
targets will also allow us to estimate the influence of metallicity on the
IMF. The team has leading-edge expertise in all the techniques required:
making the observations and reducing them to luminosity functions, converting
to mass functions, and all types of dynamical modeling, which are required to
make the small corrections to global and then initial mass functions.
================================================================================
Proposal Category: GO
Scientific Category: QUASAR ABSORPTION LINES
ID: 8125
Title: Primordial Low-z LyAlpha Clouds towards PKS 2155-304?
PI: J. Michael Shull
PI Institution: University of Colorado, Boulder

The origin of the low-redshift LyAlpha clouds remains a mystery, made more
tantalizing by the possibility that they contain a significant fraction of
baryons. Our GHRS/G160M study of PKS 2155-304 (Shull et al. 1998) identified
a cluster of strong LyAlpha absorbers between 16,000 and 18,500 km s^-1 with
N_ HI ~ 2 * 10^16 cm^-2 (Ly-edge estimate from ORFEUS). From expected
positions of Si III and C IV absorption, we set 4Sigma limits Si/C < 0.003 and
C/H < 0.005 solar abundance. Using the VLA, we identify these absorbers with
the extended halos or intragroup gas surrounding four H I galaxies offset by
(400-800)h_75^-1 kpc. PKS 2155-304 is a FUSE Key Science target for studies
of extragalactic D/H and will produce accurate N_ HI from higher Lyman series
and Lyman limits. Here, we propose to obtain a STIS/E140M spectrum (1150-1740
Angstrom) at 10 km s^-1 resolution to detect or limit metal absorption lines
(C IV, Si III, Si IV, N V, C II, Si II, S II) down to below 10^-3 solar
abundance (4 mAngstrom\ EW limit at S/N ~30) as well as D I LyAlpha. These
data will ascertain whether the IGM in these absorbers is primordial and thus
will probe the origin and chemical evolution of gas at large distances from
galaxies. The combination of a bright target (V=13.1) and high-N_HI absorbers
make this an ideal situation for studying metals in LyAlpha clouds. These
clouds have the potential for being the most metal-free gas ever studied.
================================================================================
Proposal Category: GO
Scientific Category: QUASAR ABSORPTION LINES
ID: 8126
Title: STIS OBSERVATIONS OF QSO PAIRS
PI: Patrick Petitjean
PI Institution: Institut d'Astrophysique de Paris

We propose to obtain STIS ultraviolet spectra of four QSO pairs with similar
common redshift ranges (z ~ 0.7--1) and projected linear separations gradually
increasing from ~0.5 to sim1 h^-1_100 Mpc in order to: o probe the extension
and structure of the gaseous complexes giving rise to the formation of LyAlpha
absorption lines at intermediate redshift (z ~ 0.9). The chosen scale is ideal
to investigate the transition between huge halos that induce a marked
correlation between the LyAlpha forests along lines of sight with smaller
separations and filamentary structures that are predicted by simulations; o
investigate the transversal proximity effect of the foreground quasar along
the line of sight to the background quasar; o study the environment in
which QSOs reside and in particular the presence of gas around the foreground
quasar. Given the brightness of the QSOs to be observed (B ~eq 17.9 -- 18.4)
and the spectral range of interest (1900 Angstrom <= Lambda <= 3100
Angstrom), HST + STIS provides us with the unique existing instrumental
capability to obtain the proposed observations.
================================================================================
Proposal Category: GO
Scientific Category: QUASAR ABSORPTION LINES
ID: 8127
Title: The Homogeneity of Damped LyAlpha Systems (and
Variability in BAL Systems)
PI: Eric Monier
PI Institution: The Ohio State University

-0.2 truein We propose an investigation of the damped LyAlpha line at z_abs =
1.6595 in the gravitationally lensed Cloverleaf QSO, seen in the composite
FOS-G270H spectrum of the Cloverleaf. The metal lines of the system have
been previously studied along the individual lines of sight using FOS G400H
and G570H spectra, which indicate that there are variations in the columns of
gas observed among the four sight-lines over scales of ~ 4h^-1 kpc (H_0 = 100h
km s^-1 Mpc ^-1, q_0 = 0.5). We propose STIS observations that will enable us
to measure the individual ionH1 column densities in the LyAlpha line along all
four sight-lines, the values of which will provide an indication of the size-
scale and homogeneity of the structures that give rise to damped LyAlpha
systems, important constraints on models for these systems. On these scales,
does a damped system resemble a large homogeneous structure, or are there
significant column density variations due to inhomogeneities or individual
giant hydrogen clouds? The results of the proposed observations will allow us
to consider this question. As an added benefit, the STIS observations will at
the same time allow us to reobserve the individual Broad Absorption Line
spectra of the Cloverleaf components. This information can be compared with
earlier HST-FOS G400H and G570H spectra to search for and analyze changes in
strength which are known to occur in some BAL systems. Such measurements
provide important constraints on BAL
================================================================================
Proposal Category: GO
Scientific Category: STELLAR EJECTA
ID: 8128
Title: Stalking FLIERs in Planetary Nebualae: a STIS Study
PI: Mario PERINOTTO
PI Institution: Dipartimento Astronomia

FLIERs are enigmatic pairs of small, low-ionization knots located on opposite
sides of the central star of many PNe. Their symmetric locations, equal,
opposite and supersonic Doppler shifts (Mach 3-5), and highly enriched N/O
ratios (~3-7) suggest that they are peculiar spitballs ejected recently from
the stellar interior. As expected, WFPC2 studies spatially resolved the
FLIERs and revealed the presence of bow shocks --- but unexpectedly, the tails
point precisely in the wrong direction
================================================================================
Proposal Category: GO
Scientific Category: CS
ID: 8129
Title: Rapid UV Spectroscopy of Stellar Flares
PI: Richard Robinson
PI Institution: Catholic University of America

We propose to use STIS to obtain rapid time sequence spectra of stellar
flares. The proposed observations will cover the wavelength range 2303-3111
Angstrom, which includes the expected peak of the continuum emission from the
flare, numerous Fe II lines and the Mg II resonance lines, as well as the
majority of the energy radiated in the UV/optical portion of the spectrum.
This radiation is produced by the heating of the upper photosphere and/or
chromosphere by energy propagating downward from the site of the original
energy release in the lower corona. Groundbased photometry has shown that
during the explosive phase of a stellar flare the continuum can change
drastically on time scales of seconds or less. At present there is virtually
no UV data with time resolutions capable of resolving these variations. With
the proposed data we hope to study the variation of the continuum shape during
the flare and thereby obtain some understanding of how and where the continuum
is formed. Further, in conjunction with contemporaneous radio, optical and X-
ray data, we hope to provide constraints on theoretical models of energy
transport and flare dynamics.
================================================================================
Proposal Category: GO
Scientific Category: BINARY STARS
ID: 8130
Title: Solving the ``iron curtain conundrum''
PI: Tim Naylor
PI Institution: Keele University

X-ray observations of dwarf novae in quiescence, including OY Car, show deep
and unmistakable X-ray eclipses, indicating that the boundary layer is
directly observable. However, quiescent UV spectra of OY Car indicate the
presence of veiling material, which has been modelled at a column density that
would make it impossible to observe directly the boundary layer (Horne et al.
1994). We propose to obtain phase resolved HST observations of OY Car in
quiescence, simultaneous with ASCA X-ray observations, in order to resolve
the apparent discrepancy between the X-ray and UV measurements of n_H. These
observations will also enable us to investigate the azimuthal variation of the
absorbing material.
================================================================================
Proposal Category: GO
Scientific Category: CLUSTERS, LENSING AND COSMOLOGY
ID: 8131
Title: HST Imaging of Moderate Redshift X-ray Emitting Groups of
Galaxies
PI: John Mulchaey
PI Institution: The Observatories of the Carnegie Institution of
Washington

Most galaxies in the universe, including our own Milky Way, are members of
poor groups of galaxies. Recent optical and X-ray observations of nearby
groups have revealed considerable new insight into these important systems. In
particular, there are very strong trends between the morphologies of the
member galaxies and the global group properties, such as velocity dispersion
and the presence of X-ray emitting intragroup gas. To better study evolution
in the group environment, we have embarked on a ground-based photometric and
spectroscopic survey of a large sample of X-ray selected groups at redshifts
of z=0.1-0.5. Our existing ground-based data allow us to determine group
membership, derive galaxy colors, and calculate global kinematic properties.
However, at these redshifts we lack the ability to quantify galaxy morphology,
an essential element in understanding the evolutionary effects occurring in
the group environment. Therefore, we propose to obtain WPFC2 images of a
subset of our moderate redshift sample. The high angular resolution imagery
of HST, combined with our ground-based observations, will allow us to
determine the morphological composition of moderate redshift groups, to study
how the galaxy population of groups has evolved in time, to examine the
Butcher-Oemler effect in the group environment, and to search for direct
evidence of mergers and/or galaxy-galaxy encounters in these systems.
================================================================================
Proposal Category: GO
Scientific Category: YOUNG STARS AND CIRCUMSTELLAR MATERIAL
ID: 8132
Title: The Nature of T Tauri and Herbig Ae/Be Star Winds
PI: Tom Ray
PI Institution: Dublin Institute for Advanced Studies

It is proposed to study the complex small-scale (<= 1'') dynamical and
morphological structure of the collimated outflows from the classical T Tauri
star (CTTS) RW Aur and the Herbig Ae/Be star LkHAlpha 233 using spectroscopic
imaging in HAlpha and their strong red forbidden emission lines. Seven
overlapping slit positions, parallel to each outflow but with appropriate
offsets in the transverse direction, will be used to provide 2-D intensity and
radial velocity data on the high velocity component (HVC or jet) and low
velocity (LVC) component of these flows. Using these ideal targets (ideal
because of their lack of extinction close to the source), we wish to attack a
number of fundamental questions that are generic to outflows from both low and
intermediate mass young stars: 1. What is the nature of the enigmatic LVC
observed in the forbidden emission lines of CTTSs and Herbig Ae/Be Sstars?
This component is spatially much more compact than the jet component (with an
offset typically of 0.1''--0.4'' from the star) and represents only partially
ionized gas which is flowing ~10 times slower than the jet. Understanding the
origin of this component will have profound consequences for models of magneto
-centrifugally driven outflows, since hints for broadening of this component
by rotation have already been found in ground-based data. 2. What is the
spatial intensity, velocity and excitation structure of these flows on 0.1''--
2'' scales, e.g.\ is there evidence for entrainment and velocity variations?
3. What does the transverse velocity profile of a stellar jet look like? Is
there evidence, close to the star, for a boundary layer in the jet? 4. On what
scales are jets from young stars collimated?
================================================================================
Proposal Category: GO
Scientific Category: INTERSTELLAR AND INTERGALACTIC MATTER
ID: 8133
Title: The Starburst-ISM Interaction in NGC 1569
PI: Patrick Shopbell
PI Institution: University of Maryland

We propose to use the WFPC2 camera to obtain narrowband images of the complex
ionized gas component of the dwarf starburst galaxy NGC 1569. We will image
the central regions of the galaxy in the emission lines of H Alpha, H Beta, N
Ii\ Lambda6584, [S II]\ LambdaLambda6717+6731, O Iii\ Lambda5007, and \heii\
Lambda4686. The H-alpha\ imagery will provide a map of the optical emission
associated with the filamentary ionized gas, at much higher resolution than
ever before studied. From recent ground-based imagery and Fabry-Perot
observations with 1"--2"\ resolution, we expect the increased resolution of
HST to reveal immense detail in the filament system, allowing for accurate
isolation of the filamentary structure from the background, as well as
detailed comparison of the ionized gas and stellar components. (The latter
has already been imaged in detail by HST/WFPC2.) The ionN2, ionS2, and ionO3
imagery will provide high-resolution maps of the filament excitation, leading
to improved models of the outflow emission mechanisms and energetics. The H
Beta\ image will be used to create a map of the extinction, an important issue
in the inner regions of starburst systems, and in NGC 1569 particularly.
Finally, the ionHe2 image will be used to separate regions under the influence
of Wolf-Rayet stars from those interacting with O stars, again allowing for
more accurate models.
================================================================================
Proposal Category: GO
Scientific Category: STELLAR POPULATIONS IN CLUSTERS
ID: 8134
Title: Is the IMF universal at low stellar masses?
PI: Antonella Nota
PI Institution: Space Telescope Science Institute

Our recent finding of a flat IMF below 3 M_\odot in the LMC cluster R136
raises a pressing question: is the IMF universal at low masses? We propose to
address the issue by taking deep WFPC2 images of eleven young, rich clusters
in the LMC/SMC, at different conditions of star density, metallicity and age.
We will investigate the low end of the IMF (5 - 0.5 M_\odot) with the
objective of exploring how the local conditions may impact the IMF at low
masses. By restricting the sample to the LMC/SMC, uncertainties due to
distances, reddening corrections, and field star contamination are eliminated
or largely reduced. Such effects are a major source of uncertainty in IMF
determinations of young Galactic clusters and associations. Only HST can
provide the resolution and limiting magnitude required to reach the low-mass
end of the IMF at extragalactic distances. With such a systematic study we
will be able to remove all the uncertainties related to different reduction
and analysis methods, perform a useful comparison of the results, and explore
the parameter space of the physical conditions and their impact on the IMF.
================================================================================
Proposal Category: GO
Scientific Category: CLUSTERS, LENSING AND COSMOLOGY
ID: 8135
Title: Spectroscopy of Gravitational Lens Candidates from the
HST Survey of BL Lac Objects
PI: Riccardo Scarpa
PI Institution: Space Telescope Science Institute

We propose spectroscopic observations of two new gravitational lens
candidates, 0502+675 and 1440+122, discovered in our HST R-band snapshot
survey of ~100 BL Lac objects. Each contains a double point source with
separation of only 0.3 arcsec. In each case, a candidate for the lensing
galaxy is also found. For 0502+675, a subsequent NICMOS H-band image shows
that the two point sources have similar R-H colors. STIS long-slit spectra of
each point source will determine whether these candidates are lenses and also
measure the redshift of the possible lensing galaxy. Due to the small image
separation, HST spatial resolution is essential. These two sources, if
confirmed as lenses, are particularly valuable for estimating H_0 because of
the large amplitude and rapid flux variability that characterize BL Lac
objects.
================================================================================
Proposal Category: GO
Scientific Category: AGN PHYSICS
ID: 8136
Title: Powering the narrow line regions in Seyfert galaxies -
are radio jets the key?
PI: Carole Mundell
PI Institution: University of Maryland

It has recently been argued that the energetic importance of Seyfert radio
jets has been underestimated and that jets may provide the enough mechanical
energy input to drive all the line emission in the Narrow Line Region (NLR)
via shocks, reducing or eliminating the role played by nuclear photoionising
radiation. However, despite the proximity of Seyferts, the poor angular
resolution of radio images of their `jets' (more often seen as a string of
knots rather than a jet) has prevented a direct causal relationship between
the radio jet and NLR emission from being established. The relative
contributions of direct photoionisation of emission line regions by the
central continuum source, and strong interaction of the emission-line gas with
radio plasma therefore remains controversial. For the first time, we have
imaged the underlying radio jet in NGC4151, with unprecedented angular
resolution (40 mas or 2.6pc) and here we propose matched resolution, spatially
resolved, long slit spectroscopy, to search for shock signatures due to hot
gas along the straight, fine jet. This study will provide a powerful test of
shock vs photoionisation models by utilising the full range of line
diagnostics available with STIS, ranging from the FUV to the near IR,
especially the key shock excited UV resonance lines, and will for the first
time, directly establish the effect of a Seyfert radio jet on its
surroundings.
================================================================================
Proposal Category: GO
Scientific Category: FIELD STELLAR POPULATIONS
ID: 8137
Title: Intermediate-Age Dwarf Spheroidal Galaxies in the M81
Group
PI: Mario Mateo
PI Institution: University of Michigan

A major goal of stellar populations studies of galaxies is to reconstruct the
star-formation history (SFH) of the Local Universe via observations of the
SFHs of individual, nearby galaxies and compare the result with the SFH
history derived from high-redshift galaxies. This task is nearly complete in
the Local Group (LG), but the agreement with high redshift observations is
poor. Perhaps more local galaxies must be measured to achieve a
representative sample. We propose to help enlarge the sample of nearby
galaxies with good SFH determinations by obtaining deep V,I WFPC2 observations
of UGC 4998 and DDO 44, both early-type dwarf members of the M 81 group that
exhibit clear signs of young and intermediate-age populations. These galaxies
are complementary to the mostly old, low-surface brightness M81 dwarfs
observed to date with HST. Our observations will also allow us to (a)
identify radial population gradients as a function of time in both galaxies,
(b) determine their basic chemical properties, (c) critically compare
distances derived using surface-brightness fluctuations in ground-based data,
with distances derived from the HST data using the tip of the red giant
branch, (d) place the galaxies in the global relations for other early-type
systems that relate metallicity, size, surface brightness and luminosity, and
(e) in UGC 4998, compare the stellar populations of its nucleus and off-center
globular cluster.
================================================================================
Proposal Category: GO
Scientific Category: BINARY STARS
ID: 8138
Title: Ultraviolet Spectroscopy of the X-ray Transient CI Cam
PI: Edward L. Robinson
PI Institution: University of Texas at Austin

The transient X-ray source XTE J0421+560 erupted on 1998 March 31. Transient X
-ray sources are all binary stars that contain an accreting neutron star or
black hole, but the XTE J0421+560 binary system is unusual and possibly
unique. It emitted strong, non-thermal radio flux during its eruption and
possibly ejected a pair of relativistic jets. The eruption decayed in a few
days, more rapidly than most X-ray transients. CI Cam, the optical counterpart
of XTE J0421+560, is the brightest known X-ray transient, allowing high-
resolution measurements of its spectrum. Its optical and near-infrared
spectrum is dominated by strong emission lines, with remarkably strong Fe II
emission. The spectrum shows that there is a complex circumstellar environment
containing at least two or possibly three kinematically and thermally distinct
shells. There is also a high velocity wind, which may have been produced
during the outburst. We will obtain the first ultraviolet spectrum of CI Cam.
Using the MAMA echelle gratings we will measure: the ultraviolet continuum,
the reddening, the line profiles, and the Fe II emission line ratios. From
these data will determine whether the system is a high-- or low--mass X-ray
binary, the wind structure, the physical conditions in the shells and the
accretion flow, and the cause of the anomalously strong Fe II emission.
================================================================================
Proposal Category: GO
Scientific Category: BINARY STARS
ID: 8139
Title: Probing an Ancient Thermonuclear Runaway on a White Dwarf
in a Dwarf Nova
PI: Edward Sion
PI Institution: Villanova University

We unexpectedly discovered evidence, based upon two GHRS G160M spectra, of
greatly elevated abundances of odd-numbered nuclei Phosphorus and Aluminum as
well as a Nitrogen to Carbon ratio of 10 in the photosphere of the white dwarf
in the dwarf nova VW Hydri. These abundances, if confirmed, are direct
indicators of a past thermonuclear runaway on the white dwarf and hence the
first spectroscopic evolutionary link between a dwarf nova and a classical
nova. Since we have shown that the white dwarf has a rapidly spinning
accretion belt, this raises the exciting possibility that these heavy elements
were dredged up due to shear mixing of the tangentially accreted disk matter
with the underlying white dwarf envelope material. Moreover the belt provides
a natural explanation for the very low boundary layer luminosity in VW Hydri
and, by implication, other dwarf novae. We require the higher sensitivity,
resolution, and broader wavelength coverage of STIS to (1) confirm our
detections and determine the first chemical abundances of many odd-numbered
proton capture species; (2) determine a accurate mass for the white dwarf and;
(3) probe changes in the accretion belt and surface abundances as a function
of time since a superoutburst. This study will hold important implications
for ^26Al production in the Galaxy, CVs as Type Ia SN progenitors, and the
physics of tangential (disk) accretion in other astrophysical systems.
================================================================================
Proposal Category: GO
Scientific Category: AGN PHYSICS
ID: 8140
Title: Far-UV STIS Imaging of the M87 Jet
PI: John Biretta
PI Institution: Space Telescope Science Institute

We propose far-UV STIS imaging observations as part of our ongoing
investigation of the M87 jet. The proposed observations will give the high-
frequency spectral shape and cut-off frequency throughout the jet; these are
expected to respond sensitively to the acceleration and energy loss mechanisms
at work in extragalactic jets. Our cycle 4-7 monitoring program reveals
striking evolution in the jet structure. Many components vary significantly
with time; new ones emerge, while others fade from view over just a few years.
Numerous superluminal components are seen with speeds between 2c and 6c. STIS
observations will give us the unique opportunity to study the evolution of
the high-frequency spectrum as these new features are born and fade away.
Current models place the M87 synchrotron cut-off frequency near 1500Angstrom,
making far-UV observations essential.
================================================================================
Proposal Category: GO
Scientific Category: STELLAR POPULATIONS IN CLUSTERS
ID: 8141
Title: High Quality WFPC2 Photometry for 3 Intermediate age LMC
Clusters with Multiple (?) Turnoffs
PI: R. Michael Rich
PI Institution: University of California at Los Angeles

In the course of analyzing photometry from a snapshot survey of Magellanic
globular clusters, we discovered 3 clusters with apparent double turnoffs. If
the fainter of the two possible turnoffs is the actual main sequence turnoff
point, then the clusters would fall in the putative LMC age gap from 4 to 12
Gyr. However, our team has been reluctant to proceed with publication until
better data could be obtained: we have never seen such peculiar turnoffs in
any of the more than 40 Magellanic clusters we have reduced. The double
turnoffs could be caused either by mergers, multiple bursts within a cluster,
or a bimodal metallicity distribution. We can test other explanations, e.g.
binary populations and convective overshoot. Given the very short original
exposures, we are requesting 6 orbits to obtain deep, high quality photometry
of these clusters in order to explain this phenomenon.
================================================================================
Proposal Category: GO
Scientific Category: STELLAR EJECTA
ID: 8142
Title: Orientation and Extent of the Bipolar Outflow in Beta
Lyrae
PI: Kenneth H. Nordsieck
PI Institution: University of Wisconsin-Madison

We propose to use two orthogonal orientations of the STIS spectrograph slit to
verify the orientation of the bipolar outflow in the interacting binary system
Beta Lyrae (HD174638), and to investigate the extent of the outflow in four
spectral regions of interest.
================================================================================
Proposal Category: GO
Scientific Category: CS
ID: 8143
Title: A Search for Acoustic Heating in the Chromospheres of Low
Activity Dwarfs
PI: Steven Saar
PI Institution: Smithsonian Astrophysical Observatory

Recent observations cast doubt on the importance of acoustic waves for
chromospheric heating, at least in inactive giant stars, and have set small
upper limits to their contribution to upper layers of the Solar chromosphere.
These findings contradict the widely accepted picture that acoustic heating
accounts for a significant fraction, the ``basal component'', of chromospheric
heating in inactive stars across the HR diagram. To help resolve this issue,
we propose to observe an extremely inactive (basal) dwarf star (Tau Ceti) to
search for specific signatures of upward propagating acoustic waves: blue-
shifts and enhanced blue wings in chromospheric lines. Solar data show that
the strength of blue-shift can be used to estimate the acoustic contribution
to chromospheric heating. We will also analyze archival HST data of an active
dwarf of the same spectral type, and solar spectra from the SUMER instrument
on SOHO, for comparison with the new data. Lack of a significant acoustic
signature in Tau Ceti would indicate that magnetic heating generated by a
local (turbulent, non-cycling) dynamo is responsible for the basal component
of chromospheric heating in main sequence stars. Tau Cet may be in a phase
analogous to the solar Maunder minimum, and HST spectra might serve as a proxy
for the solar spectrum in this state. The spectra will also be used for
emission measure analysis differentially between the Sun and solar-like stars.
================================================================================
Proposal Category: SNAP
Scientific Category: AGN PHYSICS
ID: 8144
Title: UV Spectroscopic Snapshots of FUSE AGN Targets
PI: Gerard Kriss
PI Institution: Space Telescope Science Institute

We propose a UV spectroscopic snapshot survey of AGN scheduled to be observed
by the Far Ultraviolet Spectroscopic Explorer (FUSE). The FUSE GTO program
includes all AGN with known far-UV fluxes in excess of 1.5 * 10^-14 erg cm^-
2 s^-1 AA^-1 over the 900--1200 Angstrom\ wavelength range. Of these, 88 are
low-redshift AGN with z < 0.3. Contemporaneous STIS/MAMA observations using
gratings G140L and G230L will give complete coverage of all UV resonance
absorption and emission lines from the Lyman limit to Mg ii. A 31-minute
snapshot with exposures divided between G140L and G230L will yield spectra
with a minimum S/N of 15 per resolution element at all wavelengths for all
these targets. In addition to the emission line measurements, we will be
sensitive to intrinsic absorption lines to a limiting equivalent width of 0.3
Angstrom\ at the 3 Sigma level. Finally, in combination with the FUSE spectra,
we will measure the continuum shape across the peak of the ``big blue bump",
permitting us to see if the 1000 Angstrom\ break found in the HST composite
quasar spectrum by Zheng et al. is present in the lowest redshift AGN.
================================================================================
Proposal Category: GO
Scientific Category: INTERSTELLAR AND INTERGALACTIC MATTER
ID: 8145
Title: Abundances and Physical Conditions in the ISM of the
Magellanic Clouds
PI: Daniel Welty
PI Institution: University of Chicago

We propose to obtain high-resolution UV spectra of seven stars in the LMC and
SMC, as part of a detailed study of the interstellar medium in and toward the
Magellanic Clouds --- nearby systems of low metallicity and low dust-to-gas
ratio for which stellar abundance data are also available. We will use the
STIS echelle modes to obtain absorption-line profiles for species such as C I,
Mg I, N I, O I, S II, Zn II, Mg II, Si II, Cr II, Mn II, Fe II, and Ni II.
These UV spectra will be used, together with optical spectra of Na I, K I, and
Ca II obtained at higher resolution and/or S/N ratio and with far-UV spectra
obtained with FUSE, to determine accurate abundances, pressures,
temperatures, densities, and radiation fields for both neutral and ionized
clouds in the LMC, SMC, and Galactic disk and halo. Determining detailed
abundances/depletions (for many elements) and local physical conditions for
diverse environments in our Galaxy and in the Magellanic Clouds will aid in
understanding the absorption-line systems seen toward distant QSO's.
================================================================================
Proposal Category: SNAP
Scientific Category: CS
ID: 8146
Title: A Search for Binary L-dwarfs
PI: Neill Reid
PI Institution: California Institute of Technology

We propose to use the unparalleled resolution of the WFPC2 Planetary Camera to
search for close binaries amongst the sample of 37 low-temperature L dwarfs,
identified primarily in the course of the DENIS and 2MASS near-infrared
surveys. Our goals are twofold: first, statistical analysis to estimate the
binary fraction amongst these very low mass objects; second, identification
of individual binary systems suitable for long-term monitoring to determine
astrometric orbits, and hence masses. Comparison with theoretical models
indicates that the L-dwarfs in our sample have temperatures of ~ 1500 < T_eff
< 2300K and luminosities of 12 < M_bol < 15, implying in most cases distances
between 20 and 60 parsecs. Given those distances, and a binary fraction and
semi-major axis distribution comparable with that amongst late-type M-dwarfs,
our previous HST observations indicate that between 15 and 20\ spatially.
These HST observations will be supplemented by near-infrared ground-based
radial-velocity measurements and deeper, but lower resolution, imaging.
================================================================================
Proposal Category: GO
Scientific Category: GALAXY POPULATIONS AND INTERACTIONS
ID: 8147
Title: Ongoing Mass Transfer in the Galaxy Pair NGC 1409/10
PI: William Keel
PI Institution: University of Alabama

WFPC2 snapshot imaging shows a dust lane connecting the members of the
strongly interacting galaxy pair NGC 1409/10, as well as polar dust structure
in NGC 1409. This is an excellent case for direct mass transfer during a tidal
encounter, and a unique chance to estimate the total mass and deposition rate
during such transfer. I propose two-color STIS imagery of this system, which
will allow a three-dimensional reconstruction of the dust geometry. The
results will show whether these dust structures in fact connect and wrap
around the recipient galaxy, making this a genuine instance of mass dumping,
for which a mass-flow rate could be estimated from broad dynamical
considerations. Two passbands are needed to break the depth/extinction
degeneracy that remains from single-passband data.
================================================================================
Proposal Category: GO
Scientific Category: SOLAR SYSTEM
ID: 8148
Title: Discrete Photometry of Galileo Mission Atmospheric
Targets in Jupiter
PI: Glenn Orton
PI Institution: Jet Propulsion Laboratory, California Institute of
Technology

We propose to investigate the vertical aerosol structure of Jupiter's
atmosphere, and its spatial and temporal variability, in conjunction with
nearly simultaneous observations by the uniquely well positions but data-rate
limited Galileo Orbiter. Our observations are targeted to broaden the
perspective of the spatially-, temporally-, and spectrally-limited sampling of
Jupiter by Galileo, providing a strategic supplement to the atmospheric
science derived from the Galileo mission. The high spatial resolution global
coverage provided by HST imaging provides an essentially component in a
larger, comprehensive research campaign to acquire and analyze synoptic
observations of Jupiter's atmosphere in order to understand its dynamic
meteorology. Besides the 5-Mum hot spots, brown barges and the Great Red Spot
to be observed by Galileo synoptically on orbits 22 and 24, we will also
characterize the evolution of two features that were observed previously by
Galileo: a residual stratospheric haze remaining from the comet Shoemaker-Levy
9 collision and a newly formed white oval. features that were
================================================================================
Proposal Category: GO
Scientific Category: HOT STARS
ID: 8149
Title: The Spectral Energy Distribution of a Neutron Star
Photosphere
PI: Frederick Walter
PI Institution: State University of New York at Stony Brook

There exists not a single direct measurement of the radius or mass of any
neutron star outside a binary system. As part of our study of the photospheres
of neutron stars, we seek to obtain the spectral energy distribution of the
isolated neutron star, RX J185635-3754. The spectrum is very nearly thermal
from 10Angstrom\ through 6000Angstrom. A STIS/MAMA FUV spectrum will sample
the brightest observable part of the continuum longward of the peak
emissivity, and will include the wavelength of the gravitationally-redshifted
Lyman Alpha line. Other data in hand include an EUVE spectrum, a second ROSAT
observation revealing a possible proper motion, and ground-based images with
detections at B and V. Second epoch HST images to measure proper motion and
parallax are planned for cycle 7. We are developing model atmospheres for
neutron stars, with an aim to using the observed spectral energy distribution
to determine the radius and surface composition of this neutron star. We will
use the measurements of radius, surface gravity, and gravitational redshift to
constrain the interior equation of state.
================================================================================
Proposal Category: GO
Scientific Category: INTERSTELLAR AND INTERGALACTIC MATTER
ID: 8150
Title: The metallicity and dust content of HVC complex C
PI: Bart Wakker
PI Institution: University of Wisconsin-Madison

From observations of S II, H I and HAlpha toward the Seyfert galaxy Mark 290,
we have recently determined that the high-velocity cloud complex C has a
metallicity ~0.07+/-0.02 times solar. Other work shows that this extensive
cloud complex is at least 3 kpc above the galactic plane and probably closer
than 30 kpc, placing it in the Galactic halo. These results make it likely
that complex C is a remnant of the formation of the Galaxy or Local Group. It
may represent a present-day analogue of the damped LyAlpha absorbers seen in
QSO spectra. Our abundance result provides the first direct observational
evidence for the infall of low-metallicity gas on the Milky Way, required in
models of galactic chemical evolution. We request time to obtain the near-UV
spectrum of Mark 290, to measure column densities for Zn, Fe, Mn and Cr. Zn
and S are produced by different nucleosynthetic pathways (S is an Alpha
element, Zn an Fe peak element) and both are usually only slightly depleted
onto dust; thus, the S/Zn ratio provides crucial information about the element
production history of complex C. Fe, Mn and Cr are usually mostly in dust
grains, so their ratios with S and Zn will tell us about the presence, amount
and properties of the dust. These observations will provide important zero-
redshift abundance information for the study of gas and dust in damped LyAlpha
systems.
================================================================================
Proposal Category: GO
Scientific Category: STELLAR POPULATIONS IN CLUSTERS
ID: 8151
Title: NGC 1866: A Critical test of Stellar Evolution for
Intermediate Mass Stars
PI: Alistair Walker
PI Institution: National Optical Astronomy Observatories

We propose to obtain V (F555W) and I (F814W) images centered on the LMC
cluster NGC 1866, with a range of exposure times such that we can measure all
cluster stars from the brightest at V ~ 15 down to V ~25. NGC 1866 has age ~
100 Myr and is so populous that the evolving stars, with M ~ 5 M_\odot, are
caught even in short phases of evolution. As such, it provides a critical test
of stellar evolution theory applicable to these intermediate mass stars. We
will prepare a color-magnitude diagram that will, for the first time, include
all the luminous evolved stars. This is impossible to achieve from ground-
based observations due to crowding. We will also measure a luminosity
function for the unevolved main sequence to M ~ 0.5 M_\odot which allows both
determination of the IMF for cluster stars with masses in the range 0.5 - 5
M_\odot and an investigation of the cluster dynamical evolution by study of
the spatial mass distribution. The deep and accurate MS photometry will also
permit precise fitting of a fiducial ZAMS, and hence derivation of a distance
relative to the Hyades, the basis of the ZAMS calibration. Since NGC 1866
contains at least 23 Cepheid variables, we will thus calibrate the Period-
Luminosity relation zeropoint, and determine the distance to the LMC relative
to the very accurate Hipparcos parallax distance to the Hyades with a minimum
of steps and assumptions.
================================================================================
Proposal Category: GO
Scientific Category: SOLAR SYSTEM
ID: 8152
Title: Mineralogy and Weathering History of Mars
PI: James F. Bell
PI Institution: Cornell University

We propose to perform high spatial resolution and moderate spectral resolution
5500Angstrom \ \ to 10000Angstrom \ STIS long-slit imaging spectroscopy of
Mars, in order to identify and globally map the planet's iron-bearing surface
mineralogy. STIS measurements would be obtained by push-broom scanning the 0.2
" slit entirely across the planet during each of four separate "visits" spaced
~6 hours apart over the course of a single Martian day. These hyperspectral
STIS image cubes will be complemented by near-simultaneous WFPC2 UV-VIS
imaging that will allow us to quantify the effects of water ice clouds or
other aerosols on our STIS spectra. These data will be used to search for and
globally map spectral signatures of climatically-diagnostic ferric and ferrous
minerals at a spatial scale comparable to existing spacecraft orbital
spectroscopy data (~20 km/pixel) and in a wavelength region not well
spectrally-sampled by existing or planned Mars spacecraft instrumentation. A
secondary objective of these observations is to provide unique new scientific
and calibration measurements in support of four NASA Mars exploration
missions. We require these observations to be scheduled near 0degrees phase
angle at opposition (24 April 1999) in order to study this poorly explored
part of the Martian phase curve and to maximize the spatial resolution.
================================================================================
Proposal Category: GO
Scientific Category: STELLAR POPULATIONS IN CLUSTERS
ID: 8153
Title: Exploring the Luminosity Function near the, Limit of
Hydrogen Burning in Globular Clusters
PI: Ivan King
PI Institution: University of California

This is a continuation of a program that has extended the color--magnitude
diagram and luminosity function of NGC 6397 into the neighborhood of the
hydrogen-burning limit (GO-6797, King et al.\ 1998). Accurate astrometry, over
a baseline of a few years, allows an excellent proper-motion separation of
faint cluster stars from the numerically dominant field stars. We propose to
take second-epoch images of a second field in NGC 6397, so as to double the
sparse numbers for that cluster, and to take second-epoch images of two rich
fields near the center of M4, plus a more outlying field. This second
cluster, with a different metallicity, will provide an even larger number of
faint stars than NGC 6397. The resulting color--magnitude diagrams and
luminosity functions will present an exciting challenge to theoreticians, as a
test of both the mass--radius and mass--luminosity relations for the
observable stars of lowest mass.
================================================================================
Proposal Category: GO
Scientific Category: HOT STARS
ID: 8154
Title: The Massive Binary Pulsar 2303+46: An unexpected
companion
PI: Marten van Kerkwijk
PI Institution: University of Utrecht

Double neutron star systems are objects of fundamental interest to physics
(tests of GR) and astronomy (sources of gravitational wave radiation, possible
progenitors of GRBs). The nature of their companion, specifically the size, is
clearly of importance for these issues and has historically motivated deep
optical observations. To our surprise and delight, we have found a faint blue
optical object within 0.25 arcsec of the location of one such presumed double
neutron star system, PSR B2303+46. From pulsar timing we know securely that
the companion is more massive than 1.2 M_\odot. We suggest that the companion
is a massive hot white dwarf formed before the pulsar; such an unorthodox
solution is possible by adding a twist to the usual evolutionary scenario.
Here, we propose UV imaging with STIS to confirm that the object is stellar,
to confirm its energy distribution is thermal, and to get a rough constraint
on its temperature. Confirmation is not only important for the reasons
discussed above, but also for our ideas about the evolution of these systems,
and of considerable interest for verifying white-dwarf cooling models. If
confirmed, the companion is the only white dwarf securely known to be so
massive, and one of only a few for which two independent age estimates are
available.
================================================================================
Proposal Category: GO
Scientific Category: STELLAR EJECTA
ID: 8155
Title: Highly collimated strings in the nebula around , Eta
Carinae - a new phenomenon
PI: Kerstin Weis
PI Institution: Universitaet Heidelberg, Institut fuer Theoretische
Astrophysik

We propose to observe a set of highly collimated strings in the nebula around
Eta Car with the HST/STIS in order to determine their physical nature and
their relation to phenomenologically similar structures in nebulae around
evolved low mass stars. Eta Car is one of the most massive stars known and a
member of the class of Luminous Blue Variables. After hydrogen core burning,
these stars enter a shortlived phase which is characterized by strong mass
loss, part of which happens in the form of bursts. One of these bursts gave
rise to the Homunculus nebula around Eta Car. The strings are faint, almost
straight features outside the Homunculus. They are characterized by a linear
velocity increase towards larger distances from the star. Only STIS
spectroscopy will give us the required spatial resolution to investigate the
ionization mechanism, the density structure, the ionizing field and the shock
parameters in the strings and their changes along the strings. This will then
allow us to determine the physical nature of the strings. Moreover, as there
are morpologically similar features in Planetary Nebulae, the so-called
FLIERS, it is of importance to investigate the relation between the strings in
a nebula around an evolved high mass star and the FLIERS in a nebula around an
evolved low mass star in order to understand the mass loss mechanism of the
different stellar types better. We request 4 orbits to carry out these
observations.
================================================================================
Proposal Category: GO
Scientific Category: BINARY STARS
ID: 8156
Title: The accretion geometry in the soft, double-pulsing
intermediate polar V405 Aur
PI: Coel Hellier
PI Institution: Keele University

The intermediate polars (IPs) show several types of behavior. Some show only
hard bremsstrahlung X-ray spectra, while others show an additional soft black-
body component. Some show quasi-sinusoidal single-peaked pulses at the white
dwarf spin period, others show double-peaked pulse profiles. We have suggested
that both dichotomies are related to the area of the accretion footprint on
the white dwarf, and hence to the process by which the magnetic field disrupts
the accretion disk. In order to confirm or refute our hypothesis we aim to
observe V405 Aur, the only IP showing both a soft X-ray component and a double
-peaked pulse profile. We will use UV STIS spectra to measure the temperature
of the pulsation, and hence deduce its emitting area (one of the most useful
pieces of information to obtain, since it can be immediately compared to the
white dwarf area to tell us where the pulse originates). We will further
compare the UV pulse profile to the optical and X-ray pulse profiles and model
all three with our simulation code to deduce their origin. Additionally, the
analysis of the UV line profiles will give us velocity information from near
the white dwarf for the first time. By putting all this information together
we can deduce the accretion geometry, and thus, by tracing field lines back to
the point where the field disrupts the disk, obtain constraints on the
(largely unknown) physics of the transition region.
================================================================================
Proposal Category: GO
Scientific Category: YOUNG STARS AND CIRCUMSTELLAR MATERIAL
ID: 8157
Title: Molecular Hydrogen in the Circumstellar Environments of T
Tauri Stars
PI: Frederick Walter
PI Institution: State University of New York

We will probe the gaseous environments of low mass pre-main sequence stars by
studying the H_2 UV Lyman bands. We have detected fluorescent H_2 Lyman band
emission, pumped by H I Lyman Alpha and Si IV, in 8 classical T Tauri stars
but not in 3 naked T Tauri stars. The former all show evidence for dusty
circumstellar disks; the latter show no evidence for dust disks. In T Tau the
H_2 emission is extended, but a large fraction of the total emission arises
within 15 AU of the star. We propose 2 investigations: 1. Where is source of
the fluoresced H_2 in the T Tauri stars? High dispersion spectra will yield
the line profiles and velocities. Gas in inner disks should evidence orbital
motions. At low dispersion, using a long slit, we can map the large-scale
spatial distribution of the molecular gas. 2. What is the gas disk survival
timescale? Do those PMS stars which show evidence of inner holes in their dust
disks have evidence of gas disks? Do the gas and dust disks dissipate at the
same time? The answers will have implications for theories of disk clearing
and planetary formation, and will provide insights into the spatial
distribution of gas near classical T Tauri stars.
================================================================================
Proposal Category: GO
Scientific Category: SOLAR SYSTEM
ID: 8158
Title: FUV diagnostic of Saturn's stratosphere with STIS. Water
influx from the ring and polar haze
PI: Renee Prange
PI Institution: Institut d'Astrophysique Spatiale

This program addresses several outstanding issues concerning Saturn's upper
stratosphere by means of UV long slit spectroscopy with STIS (6 orbits). In
the wavelength range of interest, 1150 - 3100 Angstrom, lie the signatures of
scattering by aerosols and of absorption by stratospheric species, and the
auroral H and H_2 emissions. The issues cover thermochemical equilibrium and
dynamics of the atmosphere through the abundance and latitudinal distribution
of the species (hydrocarbons, phosphine, water). We will particularly focus on
two particular issues for which we have obtained promising preliminary results
in Cycle 4 with GHRS: (i) The distribution of the abundance of heavy
hydrocarbons (identified in Cycle 4 spectra) and aerosols in the polar haze
with respect to the locus of the aurorae (their assumed source), in order to
investigate haze generation processes and transport. (ii) The latitudinal
profile of exogenous water in the atmosphere of Saturn (for which we have
detected a strong maximum at southern mid latitudes near the B-C ring
footprint in Cycle 4) . The effect of this influx on the composition of
Saturn's atmosphere will be inferred from photochemical models and compared to
observations (e.g. observed anomalies in CO, H and ionospheric densities). A
quantitative and accurate latitudinal profile of water abundance would be an
essential test of electromagnetic theories of ring erosion and of the age of
the rings.
================================================================================
Proposal Category: GO
Scientific Category: BINARY STARS
ID: 8159
Title: The UV Spectrum of an Elliptical Accretion Disk Devoid of
Hydrogen
PI: Richard Wade
PI Institution: The Pennsylvania State University

AM CVn (HZ 29) is the prototype of the interacting double-degenerate binaries,
or so-called Helium Cataclysmic Variables (He CVs), which cpould be a channel
to form Type Ia supernovae. These are short-orbital period systems in which a
low-mass He white dwarf orbits a more massive white dwarf and transfers matter
devoid of hydrogen to an accretion disk around that star. AM CVn is the best
He CV to measure the mass transfer rate (\dot M) and the chemical abundance
pattern of the transferred material. Lines from different ions of the same
element arise at different radii in the disk, and have different velocity
widths. This makes a mapping of temperature onto radius possible, and with it
a determination of \dot M. This modeling is best done using ultraviolet
spectra, where the necessary lines can be found. Observations by HST/STIS
are needed, to provide the combination of high spectral and temporal
resolution and signal-to-noise ratio, and wide spectral coverage that neither
IUE nor prior HST/GHRS spectra provide. The data can be used in a variety of
ways, thus we will make them available to the community immediately. We will
undertake a modeling study of the steady-state spectrum of AM CVn. We will
learn whether only H-burning took place in the mass donor or whether 3Alpha He
-burning also occurred. Comparing H-rich and H-depleted disks will also tell
us about the stability of disks and their ability to drive winds.
================================================================================
Proposal Category: GO
Scientific Category: STELLAR POPULATIONS IN CLUSTERS
ID: 8160
Title: A Proper-Motion Study of Two Fields, in the Globular
Cluster 47 Tucanae
PI: Ivan King
PI Institution: University of California

We propose, using only 5 orbits of HST time, to carry out high-precision
astrometry in two fields in the globular cluster 47 Tucanae in order to (1)
measure the relative proper motions in the radial and tangential directions,
for many thousands of main-sequence stars and white dwarfs, and determine the
anisotropy of stellar motions as a function of stellar mass; (2) strengthen
our current determination of the distance of the cluster, which depends on
comparing proper motions with radial velocities; (3) extend the luminosity
function of the cluster 3--4 magnitudes fainter, reaching well below
0.1\>m_\odot; (4) measure the rotation of the cluster in the plane of the sky;
(5) measure the absolute proper motion of the cluster; and (6) possibly
measure the proper motion of the Small Magellanic Cloud.
================================================================================
Proposal Category: GO
Scientific Category: HOT STARS
ID: 8161
Title: Boron in the Magellanic Clouds: A Novel Test of Light
Element Formation
PI: Kim Venn
PI Institution: Macalester College

Observations of boron abundances in the Magellanic Clouds will provide a novel
test of the assertion that boron is produced primarily through spallation
reactions between cosmic rays and ambient interstellar nuclei. The lower
metallicities and especially the lower cosmic ray flux of the Small Magellanic
Cloud, as inferred from Gamma--ray observations, imply that, if spallation is
the dominant production mechanism, boron should be significantly underabundant
in the Clouds relative to its local Galactic value. Only spectroscopy from
space can provide the necessary boron abundances. In this proposal, we are
requesting HST STIS observations to detect the B III resonance lines in one
LMC and two SMC main-sequence B stars. Only STIS can observe these NUV
lines, especially with the resolution and S/N required for reliable boron
abundance determinations. The main-sequence stars selected for this project
show no signs of stellar mixing (which could destroy B), thus they can be used
to determine an accurate, present-day, boron abundance. This abundance will be
compared with that predicted by simple models of galactic chemical evolution
using the inferred cosmic ray fluxes and interstellar abundances of target
nuclei.
================================================================================
Proposal Category: GO
Scientific Category: DISTANT GALAXIES
ID: 8162
Title: Identifying the hidden phases of galaxy evolution
PI: Simon Lilly
PI Institution: Department of Astronomy, University of Toronto

Deep surveys in the sub-mm waveband are revealing a population of very
luminous dusty galaxies at high redshifts, 0.5 < z < 3, which are; (a) as a
population, producing stars at a rate as large or larger than the optically
selected galaxy population at high redshifts and thus presumably producing a
substantial (and perhaps dominant) fraction of all stars that have ever been
produced; and (b) doing so, individually, in systems with bolometric
luminosities (i.e. star-formation rates) that are very much larger than
typically seen in the optically-selected population. Together, these suggest
that the sub-mm sources represent a major phase of galaxy evolution that is
not represented in the optically-selected samples. We are engaged in a major
study of this population using SCUBA on the JCMT. Existing HST images are
playing a crucial role in this work - both in revealing disturbed morphologies
of the identifications and in simply identifying the optically faintest
sources. But at present our HST images only cover a modest fraction of our two
main survey areas, limiting the number of sub-mm sources that can be
identified and studied in detail. We propose to observe additional fields in
our survey areas to overcome this limitation.
================================================================================
Proposal Category: GO
Scientific Category: HOT STARS
ID: 8163
Title: Trapezium Systems and Stellar Jets in 30 Doradus
PI: Nolan R. Walborn
PI Institution: Space Telescope Science Institute

30 Doradus is the nearest and best resolved extragalactic starburst, hence a
paradigm for the phenomenon. Recent NICMOS observations of the new stellar
generation being triggered by the outflows from R136 establish 30 Dor as a
prime region for investigation of massive-star formation as well. Since 1"\
already subtends 50,000 AU at 50 kpc, HST makes unique contributions to the
study of 30 Dor. A recent groundbased spectral-classification study has
provided new insights into the stellar content of 30 Dor, but many of the
targets are resolved into multiple systems in the available WFPC2 images. We
propose to obtain spatially resolved STIS blue spectroscopy of some of the
newly found multiple systems, which is essential to determine accurate stellar
tempertures and masses. Several systems each in the new and previous stellar
generations are included. The HST spatial resolution also reduces the
contamination of the stellar spectra by the nebular emission lines, which is a
critical advantage. We also propose dithered PC nebular-line images of the
young Trapezium systems Knots 1-3, which interact strongly with the
surrounding interstellar medium, forming several parsec-scale jets. Finally,
we shall do two WFPC2 pointings with continuum filters, to complete the
coverage of the field, which currently limits the search for multiple systems
and the illuminating comparisons with IR and other data.
================================================================================
Proposal Category: GO
Scientific Category: GALAXY POPULATIONS AND INTERACTIONS
ID: 8164
Title: A Search for Intergalactic Globular Clusters in A1185
PI: Michael J. West
PI Institution: Saint Mary's University

The origin of the anomalously rich globular cluster populations surrounding
many supergiant elliptical galaxies remains one of the great unsolved problems
in the study of extragalactic globular cluster systems. A number of authors
have suggested that the intrinsic globular cluster populations of such
galaxies may have been augmented by large numbers of intergalactic globular
clusters which are not bound to individual galaxies but, instead, roam freely
throughout the cores of clusters of galaxies. Although there is now
considerable circumstantial evidence in support of this view, efforts to
detect intergalactic globular clusters directly have thus far been thwarted
by the complication that most galaxy clusters have a supergiant elliptical
galaxy residing at their dynamical centre, which makes it impossible to
separate bona fide intergalactic globulars from the galaxy's own intrinsic
population. To avoid this difficulty, we propose to search for intergalactic
globulars in the rich, nearby cluster Abell 1185, since its brightest member
galaxy is offset from the X-ray centroid by ~eq 4^ (150 kpc). A series of
deep WFPC2 images centered on the peak of the X-ray distribution in Abell 1185
should reveal a population of intergalactic globular cluster if it exists. The
detection (or non-detection) of such globular clusters will provide important
new constraints on galaxy interactions and evolution in clusters.
================================================================================
Proposal Category: GO
Scientific Category: QUASAR ABSORPTION LINES
ID: 8165
Title: Pervasive Hot Gas Hidden in Galaxy Groups: A Substantial
Baryon Reservoir?
PI: Edward Jenkins
PI Institution: Princeton University Observatory

We propose to use STIS to search for hidden and pervasive hot gas in the
intracluster media of groups of galaxies. Cosmological simulations predict
that at z ~ 0, most groups of galaxies should be embedded in large filaments
and sheets of shock heated gas at 10^5 -- 10^6 ^degreesK. This hot gas may
contain a substantial fraction of the baryons in the universe at the present
epoch, but its quantity and existence is not firmly established because gas in
this temperature range is difficult to detect in x-ray emission. However, it
can easily be detected via absorption lines of highly ionized species such as
O VI. We propose to observe H1821+643 and PG1116+215 to search for O VI and
broad H I LyAlpha absorption due to the intracluster media of thirteen known
galaxy groups pierced by the sight lines. Toward H1821+643, we have already
discovered O VI absorption associated with a galaxy group at z = 0.225 using
low resolution HST GHRS spectra, but we could not determine if the O VI
absorber is collisionally ionized or photoionized. With the vastly improved
resolution and sensitivity provided by STIS, we will be able to identify the
ionization mechanism in this absorber by (1) searching for broad H I
absorption in collisionally ionized gas or narrow H I indicative of
photionized gas, (2) measuring C II/C III/C IV and Si II/Si III/Si IV, and (3)
examining the velocity widths of low and high ionization stages.
================================================================================
Proposal Category: GO
Scientific Category: GALAXY STRUCTURE AND DYNAMICS
ID: 8166
Title: WFPC2 Narrow--Band HAlpha Imaging of the Edge-on Galaxy
NGC4631
PI: Q. Daniel Wang
PI Institution: Northwestern University

Observations of nearby edge-on disk galaxies are essential to determine the
role that the disk/halo interaction has in galaxy evolution. Located in a
direction of exceptionally low Galactic extinction, NGC4631 is particularly
suitable for a multi-wavelength investigation of extra-planar gas components.
In fact, NGC4631 is one of the most well studied late-type disk galaxies.
Broad-band optical, near-infrared, near-UV, and far-UV observations have been
(or will be) taken with HST\ and \fuse. We have obtained \axaf\ observing time
to conduct a spatially-resolved X-ray spectroscopic observation of the galaxy.
Here we propose for HST\ WFPC2 narrow--band H-alpha\ imaging of the galaxy's
active central region. This image will enable us to resolve various narrow
filaments of warm ionized gas that extend more than 2 kpc away from the mid-
plane of the galaxy. Based on the geometry, filling factor and line intensity
of the filaments and their correlation with X-ray-emitting gas, we will study
their origins (chimney walls, blisters, condensations of cooled hot gas,
shocks, etc). The results will be invaluable for our understanding of similar
extra-planar gas observed in the Milky Way and other galaxies.
================================================================================
Proposal Category: GO
Scientific Category: DISTANT GALAXIES
ID: 8167
Title: WFPC2 Imaging of a Galaxy at z = 5.34 and its Field
PI: Daniel Stern
PI Institution: University of California, Berkeley

We propose to obtain deep WFPC2 images of a galaxy at z=5.34 and its
surrounding field. The galaxy, 0140+326 RD1, was the first spectroscopically
confirmed object at z > 5 and among the few confirmed objects at z > 5
currently. Our goals are to (1) map the Ly-alpha line--emitting region, (2)
study the restframe UV continuum morphology, (3) search for companion Ly-alpha
--emitting sources, and (4) study the stellar population and dust extinction
in this distant system in conjunction with recently obtained NICMOS F160W
images. If this galaxy is a truly primeval object in the process of forming
its first generation of stars, its morphological properties can provide
critical information on the earliest phases of galaxy formation. Ongoing,
deep, multi--wavelength, ground--based efforts make this an ideal field for
HST to underlinesimultaneously provide high--resolution morphological
information on several other timely issues in extragalactic astronomy: the
proposed WFPC2 pointing contains several sub--mm sources detected in a deep (~
40 ksec) program with SCUBA; the most distant known radio galaxy, 6C 0140+326
at z=4.41; 2 confirmed and several candidate Lyman--break galaxies at z ~gt 4;
and several unusually red galaxies. The observations proposed here cannot be
accomplished from ground--based facilities, as their success depends upon the
high spatial resolution and low sky background only attainable with HST.
================================================================================
Proposal Category: GO
Scientific Category: HOT STARS
ID: 8168
Title: The Optical Counterpart of the Soft Gamma-ray Repeater
1900+14
PI: Shri Kulkarni
PI Institution: California Institute of Technology

The soft gamma-ray repeaters (SGR), of which only four are known, are likely
an exotic class of neutron star known as magnetars with ultra-strong surface
magnetic fields (10^14-10^15 G). We have recently detected a radio synchrotron
nebula or "afterglow" toward SGR 1900+14 which is powered by the particle
outflow that accompanied a period of intense high energy bursting activity.
The discovery of this afterglow has allowed a sub-arcsecond position to be
determined for this source. HST observations are essential to overcome the
crowding which is present along this line of sight. We request STIS time to
identify the optical counterpart of SGR 1900+14 in hopes that it may shed
further additional light on the fascinating SGR phenomena.
================================================================================
Proposal Category: GO
Scientific Category: SOLAR SYSTEM
ID: 8169
Title: HST-Galileo Io Campaign
PI: Fran Bagenal
PI Institution: University of Colorado

Io plays a central role in the Jovian system, yet the mechanisms that couple
its volcanoes, the tenuous \sots atmosphere, the escaping corona and the
plasma torus remain elusive. In 1999 there is the unique opportunity to
combine HST observations with the Galileo close flybys of Io. A team
comprising 40 experienced Io observers, modellers and theorists have come
together to propose a campaign of HST observations that will address 4
critical issues concerning Io's enigmatic behavior: 4 pt noindento What do
the compositions of plumes and surface deposits reveal about Io's volcanism?
noindento How is Io's SO_2 atmosphere affected by volcanic activity?
noindento How does Io's atmosphere interact with the surrounding plasma
environment? What are the unidentified atmospheric emitters detected by
Galileo? noindento What powers the Io torus emissions? 4 pt The team
proposes an observing campaign of 12 targets over 35 HST orbits using WFPC2
and STIS to address these 4 tasks. On their own these HST observations will
answer many issues of the emissions from Io's surface and plumes, atmosphere,
corona and plasma torus. The synergy of combined HST and Galileo observations
provides a powerful scientific opportunity that will not be repeated in the
foreseeable future.
================================================================================
Proposal Category: GO
Scientific Category: GALAXY POPULATIONS AND INTERACTIONS
ID: 8170
Title: Kinematics of the Young Star Clusters and the Gas in the
Antennae Galaxies
PI: Bradley Whitmore
PI Institution: Space Telescope Science Institute

We propose to follow up on our discovery of over 1000 young star clusters in
``The Antennae'' (NGC 4038/4039) by obtaining long-slit and slitless spectra
of a representative sample of clusters with STIS. These young clusters have
the luminosities, colors, and radii expected of young globular clusters and
must have formed during the ongoing merger. Because of their proximity and
early stage of merging, the disks of NGC 4038/4039 form an ideal laboratory to
study cluster formation in progress. While we have GHRS spectra of two bright
clusters, the greater sensitivity and two-dimensional capabilities of STIS
will allow us to systematically study the kinematics of the stellar and
gaseous components at unprecedented spatial resolution over a large fraction
of the galaxy. In particular, we will be able to determine whether the
velocity dispersion of the clusters increases with age, as would be expected
as the process of ``violent relaxation'' turns two disk systems into an
elliptical galaxy. In addition, more accurate measurements of ages from the
long-slit spectra will provide an important consistency check on our earlier
work using UBVI photometry and H Alpha\ imaging, and will make a variety of
new studies possible (e.g., a search for evidence of propagating star
formation).
================================================================================
Proposal Category: GO
Scientific Category: SOLAR SYSTEM
ID: 8171
Title: HST Far-UV Imaging and Spectra of Jupiter's Aurora During
the Galileo Extended Mission
PI: John T. Clarke
PI Institution: University of Michigan

This proposal is for far-UV imaging and spectroscopy of Jupiter's auroral
emissions concentrating on the nature of the satellite auroral footprints in
Jupiter's atmosphere. These observations will be scheduled close in time with
Galileo spacecraft measurements of Jupiter's magnetospheric properties and UV
emissions during the GEM mission's final orbits through 1999. In our cycle 7
program to study Jupiter's aurora, we have recently identified 1) an extended
trail of auroral emission in the wake region beyond Io's magnetic footprint,
and 2) auroral emissions from Ganymede's magnetic footprint on Jupiter. Given
the emphasis of the GEM mission on the major satellites, we plan to
concentrate in cycle 7 on more detailed studies of the electromagnetic
interactions between the satellites and Jupiter. The images that we will
obtain will also allow us to continue our study of Jupiter's auroral
morphology, including updating the magnetic field model and studying dynamic
behavior reflected in persistent latitudinal motions of the auroral oval in
the morning and afternoon sectors. Because Galileo can only obtain limited
dynamic range images of the visible nightside aurora under special
circumstances, the HST observations are key to the interpretation of the
Galileo magnetospheric and auroral data.
================================================================================
Proposal Category: GO
Scientific Category: QUASAR ABSORPTION LINES
ID: 8172
Title: STIS Deep DLA Imaging Survey II
PI: Palle M\oller
PI Institution: European Southern Observatory, Garching

Using STIS we will obtain deep images of 20 high--z damped Ly-alpha galaxies
at 1.8 m_R=27.9, at rm S/N>6, as close as 0.4" (~ 1.4 h^-1 kpc) to the quasar line
of sight. The damped Ly-alpha galaxies contain nearly all neutral gas in the
Universe, so at high redshift they are the reservoirs from which today's stars
formed. However quasar absorption--line studies do not provide sizes or
morphologies, so they could be either large disks, or small e.g. more numerous
proto--galactic subunits. Deep imaging can resolve this issue, and HST is
required because the galaxies are very faint, and lie typically within 1" of
the quasar. Our STIS survey is aimed at measuring impact parameters, UV
continuum sizes, and star--formation rates of high--z DLA galaxies. With
NICMOS we extended this study to the near--IR with deep H--band imaging of 20
DLA galaxies. These observations will provide the crucial rest--frame UV--
optical colors and optical sizes and morphologies. This proposal is to now
complete STIS imaging of the NICMOS sample. The HST imaging together with
ground--based spectroscopy will unify absorption--line studies and faint
galaxy imaging studies, providing a comprehensive picture of the history of
assembly, star formation, gas consumption, and chemical enrichment in the DLA
galaxies.
================================================================================
Proposal Category: GO
Scientific Category: AGN HOSTS AND ENVIRONMENT
ID: 8173
Title: Alignment and evolution of redshift one radio galaxies
PI: Philip Best
PI Institution: Sterrewacht Leiden

vspace*-2mm The galaxies associated with powerful distant radio sources are
the most massive ellipticals known at early cosmic epochs, and are also
uniquely important for understanding the physics of AGN and the interactions
between the radio source and its environment. Our HST observations of a
complete sample of powerful 3CR radio galaxies at redshift z ~ 1 reveal
detailed small--scale structures aligned along the radio axis of these
sources. In combination with deep emission line studies, we have shown that
the properties of the host galaxies change dramatically throughout the
lifetime of the radio source, being dominated in the small sources by the
effects of the shocks associated with the radio activity. To allow
quantitative measurements of the on-going physical processes and the nature of
the surrounding environment, the importance of the radio beam power must be
determined. To tackle this issue, in cycle 6 we began a project using WFPC2,
imaging 5 galaxies from a complete subsample of 11 lower radio power 6C
sources. The first results show that the 6C galaxies also possess aligned
optical emission, but at lower flux densities than the 3CR galaxies.
Comparison with our new VLA data shows radio--optical correlations on kpc
scales. We now propose to finish the WFPC2 observations of our complete VLA
subsample. This larger sample of galaxies over a wide range of radio sizes
will allow an investigation of the evolution of the host galaxy properties
following the passage of lower power radio jets.
================================================================================
Proposal Category: GO
Scientific Category: STELLAR POPULATIONS IN CLUSTERS
ID: 8174
Title: Internal Velocity Distribution in Globular Clusters, II
PI: William van Altena
PI Institution: Yale University

We propose to determine the internal velocity distribution of the globular
clusters NGC 6205 (M13) and NGC 6656 (M22) in their cores and, for NGC 6656,
as a function of distance from the cluster center, and thus also infer its
mass distribution. In addition to measuring the velocity dispersion and any
anisotropy to 1 km s^-1 for various classes of stars, ( e.g. giants, dwarfs,
blue stragglers), we hope to better quantify the suspected rotation (and hence
cluster inclination) apparent in both of these clusters' radial velocity data.
We will also derive kinematic distances for the two clusters by comparison to
existing radial velocity data. These distances would be good to 1-3\ if the
radial velocity data were of the expected accuracy of the proper motions.
Instead, we will be limited by the radial velocities to 6\ accuracy, which
should still have considerable impact on the derived luminosities of the RR
Lyrae stars and their role in the cosmological distance scale. The HST
Astrometry Science Team obtained GTO first-epoch exposures of the above
clusters and three others (NGC 104, NGC 6752, and NGC 7078). The HST AST and
its collaborators were granted Cycle 7 GO time to observe these latter three
clusters and those observations are currently pending. In this proposal, we
are requesting second-epoch exposures under GO time for the remaining two
clusters, NGC 6205 and NGC 6656.
================================================================================
Proposal Category: GO
Scientific Category: CLUSTERS, LENSING AND COSMOLOGY
ID: 8175
Title: A Survey of Gravitational Lenses as Cosmological Tools
III
PI: Emilio Falco
PI Institution: Smithsonian Astrophysical Observatory

Gravitational lenses are powerful tools for studying cosmology, galactic
structure, and galaxy evolution. Such studies require large, uniform sets of
photometric observations and must be conducted from space because typical
image separations are ~1". CASTLES ( CfA- Arizona- Space- Telescope- LEns-
Survey) is an ongoing survey of known lensed systems. Some of its goals are:
to create a complete, uniform high-resolution photometric sample of the known
galaxy-mass lenses; to obtain redshift estimates for all lens galaxies which
lack spectroscopic redshifts; to find any source or lens components that have
escaped detection and determine their photometric properties; to obtain
precise astrometric data for all source components to improve lens models and
estimates of H_0; and to investigate the wide field environments of the lens
galaxies and their role in lensing. We propose to obtain WFPC2 V and I images
of the 14 new lens systems discovered after previous CASTLES proposals; to re-
image 13 lens systems with inadequate non-CASTLES observations; to image 2
systems that were excluded from CASTLES due to orbit cutbacks; and to obtain
WFPC2 I images of 5 binary quasars. We again would waive any proprietary
period for our data.
================================================================================
Proposal Category: GO
Scientific Category: CS
ID: 8176
Title: Confirmation and Characterization of Brown Dwarfs and
Giant Planets from NICMOS 7226/7227
PI: Glenn Schneider
PI Institution: University of Arizona

A systematic search for giant planet and brown dwarf companions to stars in
the solar neighborhood is a cornerstone of the NICMOS IDT's Environments of
Nearby Stars (EONS) program. A carefully selected candidate list of 74 stars
is currently being observed using the NICMOS coronagraph at 1.6Mum. We have
found 8 objects as faint as H=20, up to 13 magnitudes fainter than their
primaries with separations less than 5", which have very high probabilities of
being true substellar companions. For the stars in our sample this covers
minimum physical separations of 1.2-50 AU at the inner spatial detection
limit. The lower mass limit depends on age, distance, and spectral type, but
is as low as 3-5 M(Jupiter) for many of our targets. We are now requesting
time for critical spectrographic observations to characterize the physical
nature of the putative companions we have discovered. Our proposed
observations will address fundamental questions such as: Is there a continuity
of objects across the substellar mass spectrum bridging the main sequence to
planetary objects? What is their frequency of occurrence? At what distances
are they found from their primaries? And, what implications will these
discoveries have for our understanding of stellar/planetary formation
mechanisms?
================================================================================
Proposal Category: GO
Scientific Category: CLUSTERS, LENSING AND COSMOLOGY
ID: 8177
Title: Investigating Type Ia Supernovae and an Accelerating
Universe
PI: Brian Schmidt
PI Institution: Mt. Stromlo & Siding Spring Observatories

The results from the high-z supernova groups that the Universe is accelerating
rests entirely on the observation that the distant SN Ia are 0.25 magnitudes
fainter than expected for an empty Universe. While both groups have argued
that this magnitude offset is not due to quantifiable systematic effects, it
is critical to test this assumption in new ways. We propose to use WFPC2 to
obtain rest frame U and B photometry for four z~ 0.85 SN Ia. These
observations will be coupled to ground-based rest frame V photometry and
spectra. These data, combined with previous samples, will extend the D_L vs. z
diagram for SN Ia to z~0.85, and allow us to discriminate the redshift
dependence of supernova apparent magnitudes in an accelerating Universe from
that expected to result from systematic effects such as age of the stellar
population, chemical evolution, a drift in the properties of dust, and weak
gravitational lensing. Evolution of SN Ia is a primary concern and it is only
by careful object by object comparison that subtle effects will be apparent.
We therefore also propose to use WFPC2 to obtain rest frame B and V photometry
for four z~ 0.5 SN Ia. These data will be combined with extensive Keck spectra
and rest frame U and R photometry obtained from the ground. The four z~ 0.5
objects will have light curves and spectra of comparable quality to nearby SN
Ia, and will provide a basis for a detailed comparison.
================================================================================
Proposal Category: GO
Scientific Category: STELLAR EJECTA
ID: 8178
Title: Tracking the Evolution of the Homunculus and Outer Debris
in Eta Carinae
PI: Jon A. Morse
PI Institution: University of Colorado

We request Cycle 8 and Cycle 10 WFPC2 images of Eta Carinae in order to track
the expansion of high-velocity material ejected during one or more giant
outbursts of the central supermassive star. These images will increase the
time baseline from 2 to 6 years of high-resolution Planetary Camera data for
measuring proper motions and monitoring photometric changes in the debris
field. Assuming a distance to Eta of ~ 2300 pc, we will be able to trace
transverse motions of the debris of \ltsim 20 km s^-1 with the full 6 year
time baseline. PC1 images in red and blue continuum filters will be used to
track the expansion of the dusty bipolar lobes of Eta's ``Homunculus'' and
equatorial skirt of ejecta. WF3 emission-line images will be used to trace
motions of the outer debris field ~ 10'' - 40'' from the central star. This
investigation will resolve the recent controversy surrounding the kinematic
ages of the Homunculus lobes versus the equatorial skirt; whether or not these
structures are co-eval has enormous implications for models of the outburst
that created the Homunculus. We also can uniquely address issues of
hydrodynamic expansion and wind-wind interactions through a time series of
exposures of this textbook bipolar system. Because many groups around the
world who are working on different facets of Eta Carinae will be interested in
these images, we waive the proprietary rights to the dataset in order to
maximize its usage.
================================================================================
Proposal Category: GO
Scientific Category: HOT STARS
ID: 8179
Title: THE COMPOSITION AND EVOLUTION OF EXTREMELY HOT DA WHITE
DWARFS
PI: Martin Barstow
PI Institution: University of Leicester

We propose high S/N (15:1 to 30:1) STIS far UV observations of the hottest
known DA white dwarfs. With temperatures in the range 70,000-130,000K, these
stars represent an important but little understood link between the H-rich
central stars of planetary nebulae (CPN) and the general population of DA
white dwarfs. Stellar temperatures are extremely difficult to determine in
this range and depend upon knowledge of the photospheric composition, which is
also a mystery. Consequently, their relationship to the cooler DA stars
remains undefined. Far UV measurements of the abundances of heavy elements are
essential for an ultimate determination of the stellar temperature. Coupling
STIS data with an analysis of the Lyman lines obtained with planned FUSE
observations, it will be possible to determine the physical parameters of
these objects and finally track their evolution along the DA cooling sequence.
In addition, we will search for evidence of mass outflow, in the form of
blueward asymmetries in the heavy element line profiles, which is believed to
cause departures from the compositions predicted by radiative levitation
theory but which has been observed in only two DA white dwarfs.
================================================================================
Proposal Category: GO
Scientific Category: INTERSTELLAR AND INTERGALACTIC MATTER
ID: 8180
Title: The Lyman continuum radiation from galaxies
PI: Jean-Michel Deharveng
PI Institution: Laboratoire d'Astronomie Spatiale

The amount of ionizing radiation released into the intergalactic medium by
star formation is a poorly known but crucial parameter. This parameter would
tell how the galaxies can complement the contribution of quasars for ionizing
the IGM, especially at the epoch of re-ionization when the number density of
quasars appears to decline. Direct measurements of the Lyman continuum
radiation from galaxies are difficult and scarce. Indirect evaluations using
models or theoretical arguments are plagued by the uncertainties on the Lyman
continuum (\Lyc) escape fraction. We would like to take advantage of the
ultraviolet sensitivity of the G140L grating of STIS to detect (or set
significant upper limit on) the \Lyc\ radiation of star-forming galaxies in
the redshift range 0.35 -- 0.6. We have selected four objects with an H Beta\
flux (or equivalent) that warrants the detection of a \Lyc\ escape fraction as
low as 5\
================================================================================
Proposal Category: SNAP
Scientific Category: HOT STARS
ID: 8181
Title: Resolving Sirius-like Binaries
PI: Martin Barstow
PI Institution: University of Leicester

Space-based UV and EUV surveys have revealed a new population of detached
binary systems, comprising main-sequence primaries that dominate the optical
light, with hot white-dwarf secondaries that are revealed only at short
wavelengths. We propose a snapshot survey in order to search for resolved,
Sirius-like systems among these candidates. Subsequent determinations of the
visual orbits of the resolved binaries with HST will provide dynamical
measurements of the white-dwarf masses. Since there are only a very few
dynamically determined white-dwarf masses at present, this programme could
lead to a doubling or tripling of the number known. As a result, this sample
will yield direct observational data on the white dwarf mass-radius and
initial-mass ash final-mass relations and provide important tests of the
respective theoretical models.
================================================================================
Proposal Category: GO
Scientific Category: INTERSTELLAR AND INTERGALACTIC MATTER
ID: 8182
Title: The Extent of Metal Transport in the Low Redshift
Intergalactic Medium
PI: John Stocke
PI Institution: University of Colorado, Boulder

We propose to detect or at least place strong upper limits on the abundance of
C IV in 7 strong (280-740 mAngstrom\ equivalent width) low-redshift LyAlpha
absorption systems along the line of sight to the bright quasar H1821+643.
This quasar lies in an extensively surveyed field, so that all LyAlpha
absorbers are known to be within 10^2-10^3 kpc of a neighboring luminous
galaxy. We will be sensitive to C IV absorption at the 15-30 mAngstrom\
level, well below the average C IV equivalent width associated with low-
redshift LyAlpha absorbers of this strength, as inferred by line-stacking
techniques using FOS data. The C IV measurements will begin to map the extent
of the metals associated with galaxies or with the large-scale environment in
which they form. Measurements of higher Lyman series lines scheduled for FUSE
or already available will constrain the H I column density and hence the
metallicity. As a result, initial studies of the metallicity gradient of the
intergalactic medium (IGM) at large distances from luminous galaxies will be
possible. Such studies are possible only at the lowest redshifts, where we
know the locations of the LyAlpha clouds from HST spectroscopy and the
galaxies from ground-based redshift surveys.
================================================================================
Proposal Category: GO
Scientific Category: AGN HOSTS AND ENVIRONMENT
ID: 8183
Title: Morphology of the most massive galaxies in the early
universe
PI: George Miley
PI Institution: Sterrewacht Leiden

High redshift radio galaxies (HzRGs) are fundamentally important probes of
galaxy and cluster formation. They are amongst the most massive galaxies in
the early Universe and located in dense cluster environments. Our previous
WFPC2 data have revealed that HzRGs are remarkably clumpy on a sub-kiloparsec
scale, reminiscent of simulations of forming massive ellipticals. Surprisingly
our NICMOS images often show clumpy aligned morphologies unlike those expected
from an old elliptical population. There is a wide diversity in HST
morphologies and colour distributions for the 9 objects for which we have both
WFPC and NICMOS images. We propose to observe obtain WFPC2 images of 10
additional z ~ 2 radio galaxies for which we have NICMOS but no WFPC2 images.
The new data will be used to (i) determine the range of clumps colour
distributions, thereby constraining the formation history and the nature of
the radio/optical alignment effect (ii) compare them with the colours of Lyman
--break galaxies (iii) compare them with dust properties and the surmised axis
of the jet orientation (iv) confirm relationships between clumpiness and other
HzRG properties indicated by our present small sample. These observations will
comprise part of a multiwavelength study of HzRGs, involving SCUBA on the JCMT
as well as Keck and the VLT.
================================================================================
Proposal Category: GO
Scientific Category: GALAXY STRUCTURE AND DYNAMICS
ID: 8184
Title: The Origin of cD Envelopes
PI: Patrick C\^ote
PI Institution: California Institute of Technology

Approximately 20\ Located at the dynamical centers of their host cluster or
subcluster, these supergiant elliptical galaxies show extended, diffuse
stellar envelopes which trace the gravitational potential of the surrounding
cluster. A leading model for their formation involves the growth of cD
envelopes through mergers and/or tidal stripping of other cluster galaxies.
Unfortunately, the envelopes have extremely low surface brightness, making
direct observational tests of this model using either spectroscopy or
broadband colors virtually impossible. On the other hand, globular clusters
(GCs) are ideal tracers of the underlying stellar populations of cD envelopes.
Since the mean metallicity of GCs is known to depend strongly on the total
luminosity of the galaxy in which they form, an inescapable implication of cD
envelope formation through mergers or tidal stripping is that the total
luminosity of the envelope progenitor galaxies must be imprinted in the
metallicities of the GCs now associated with these galaxies. We propose to use
the superb imaging capabilities of HST to measure colors, and hence
metallicities, for several hundred GCs surrounding six nearby cD galaxies. Our
short program will triple the number of cDs having accurate GC metallicity
distributions, and will provide the first strong constraints on the
luminosities of the progenitors of cD envelopes.
================================================================================
Proposal Category: GO
Scientific Category: AGN HOSTS AND ENVIRONMENT
ID: 8185
Title: Optical Nuclear Hotspot in NGC 1068
PI: Robert Antonucci
PI Institution: University of California, Santa Barbara

Early HST observations by Lynds Etal\ revealed a nuclear optical ``hotspot"
with FWHM ~ 0.''25, now known to be displaced ~ 0.''1 from the most probable
location of the `hidden' nucleus. The nature of the hotspot is mysterious and
will be addressed by a high SNR STIS spectrum, combined with existing
polarimetric observations.
================================================================================
Proposal Category: GO
Scientific Category: GALAXY STRUCTURE AND DYNAMICS
ID: 8186
Title: The Properties of Gaseous Halos Around Disk Galaxies
PI: Joel Bregman
PI Institution: University of Michigan

Gaseous halos are key components in the structure and evolution of spiral
galaxies and here we propose to advance our understanding of these phenomena
through absorption line studies of the halo gas around the LMC and the edge-on
galaxy NGC 891. In the LMC we will determine the spatial extent of the halo
and the mass of highly ionized gas by measuring the CIV line strength against
three bright background AGNs at different disk locations. For the edge-on
system NGC 891, we will observe an AGN that we discovered whose sightline
passes through the X-ray, radio, and HAlpha halos, only 5 kpc from the disk.
By observing the Mg II and Fe II resonance absorption lines, we will measure
the filling factor, density, and pressure of this halo material and determine
the mass of gas that cools at this height above the disk.
================================================================================
Proposal Category: GO
Scientific Category: DISTANT GALAXIES
ID: 8187
Title: STIS Imaging of the Deep NICMOS Parallel Fields: Building
on the NICMOS Legacy
PI: Patrick McCarthy
PI Institution: Observatories of the Carnegie Institution of Washington

We propose to use the STIS/CCD to image 15 high latitude field imaged with
NICMOS as part of the public parallel program. The STIS images will yield
visual morphologies to magnitudes of 24.5 and quantitative measures of image
structure to 26.5 or fainter in two orbits. These data will allow us to 1)
derive the morphologies of a sample of HAlpha selected L^* galaxies at 0.7 < z
< 1.9, 2) assess the impact of patchy extinction on the population of very red
galaxies, and 3) compare the rest-frame visible and UV morphologies of a large
number of galaxies over a wide range of luminosities and colors to understand
the degree to which optical selection biases our view of galaxy evolution.
This modest investment of observing time will complement the Hubble Deep
fields and will greatly enhance the value of the NICMOS, STIS and WFPC2
archive of faint galaxy data.
================================================================================
Proposal Category: SNAP
Scientific Category: STELLAR EJECTA
ID: 8188
Title: Snapshot Spectroscopic Diagnostic Survey of the Symbiotic
Stars
PI: Charles D. Keyes
PI Institution: Space Telescope Science Institute

We propose to obtain G140L and G230L STIS spectra and nearly contemporaneous
ground-based optical spectra of as many as possible of the known symbiotic
stars for which no usable ultraviolet data exist. Currently, reliable
fundamental parameters are available for only 10 percent of the approximately
150 known or suspected symbiotics. For the components of many individual
systems, we will determine physical parameters such as Zanstra temperatures,
emission line diagnostic electron temperatures and densities, and limits on
red giant wind velocity laws and mass-loss rates. More importantly, we will be
able to establish meaningful statistical limits on the nature of hot component
sources of ionization and fundamental wind parameters, which are vital steps
toward understanding the accretion hydrodynamics and the evolutionary status
of symbiotic systems.
================================================================================
Proposal Category: GO
Scientific Category: DISTANT GALAXIES
ID: 8189
Title: The Source of Gamma Ray Bursts and the Nature of their
Hosts
PI: Andrew Fruchter
PI Institution: Space Telescope Science Institute

We propose to use the unique high-resolution optical and ultraviolet
capabilities of HST to investigate the physics of gamma-ray bursts (GRBs) and
the nature of their host galaxies. Our approach is three-pronged: 1) rapid
ultraviolet spectroscopy obtained within days of several outbursts will allow
us to probe the physics of the relativistic fireball and constrain the density
of the surrounding medium and the dust extinction in the host to the fireball,
and in many cases will provide the redshift of the GRB; 2) ultraviolet
spectroscopy and imaging will allow us to obtain redshifts of host galaxies
which cannot be found by Keck or the VLT (due to a lack of strong visible
lines in the redshift range 1.3 < z < 2.4), permitting us to measure the rate
of GRBs as a function of cosmological time; 3) optical images of the hosts
taken both shortly after outburst and up to a year later will permit a study
of the morphology of the hosts, determination of the position of the burst on
the host to 100 pc accuracy, and examination of the late time behavior of the
afterglow. The morphology and astrometry will provide a crucial discriminant
between models for the creation of GRBs; the long-term behavior of the light-
curve probes the density of the host ISM and the energetics of the fireball.
This comprehensive set of observations will provide new insights into the
astrophysics of GRBs and their high redshift host galaxies.
================================================================================
Proposal Category: GO
Scientific Category: AGN HOSTS AND ENVIRONMENT
ID: 8190
Title: The Nuclei of `Warm' Ultraluminous Infrared Galaxies --
Superstarbursts or AGN
PI: David Sanders
PI Institution: University of Hawaii

We propose high resolution spectroscopy with STIS of four of the nearest
`warm' ultraluminous infrared galaxies (ULIGs) that were discovered in the
IRAS database, and for which we have recently obtained WFPC2 images in B,I
filters. These objects are thought to represent a critical evolutionary link
between ULIGs and optically selected QSOs. Recent observations also suggest
that these objects were much more numerous at high redshifts (z = 1-4), and
that they may account for a substantial fraction of the far-
infrared/submillimeter as well as X-Ray background.. Our Cycle 5 PC
observations show that the nuclear regions (<1-2^ ) of all of these objects
appear to contain a population of massive star clusters (M ~ 10^6-10^8\
M_\odot), plus one or two `super knots' that are either the most massive star
clusters yet observed (M > 10^10\ M_\odot
================================================================================
Proposal Category: GO
Scientific Category: DISTANT GALAXIES
ID: 8191
Title: The Faintest Radio Galaxies: Interacting Starbursts at
z<1
PI: James Lowenthal
PI Institution: University of Massachusetts

We propose deep WFPC2 imaging and STIS slitless spectroscopy of two of our
ultra-deep VLA fields. Those 4- and 6-cm maps have 1-Sigma levels of 3 and 11
Mu-Jy, respectively, comparable to VLA observations of the HDF, and show 14
and 9 sources in statistically complete samples. Keck spectroscopy and
imaging to B, R, I ~26.5 have identified most of the sources as compact,
luminous starbursting and interacting galaxies at redshifts z es1; about 25\
at z>1.5. Our goals here are: (1) identify the remaining sources; (2)
pinpoint regions of star formation; (3) quantify the incidence of interaction
using spatially-resolved kinematics; (4) quantify morphologies; and (5)
constrain the evolution of these faintest of radio sources. Only the HDF and
one other field have such deep VLA, HST, and Keck data, and there is strong
evidence that field-to-field variations are significant. WFPC2 images with
F814 will provide the resolution needed to measure morphologies on sub-kpc
scales, identify interaction-induced star-formation, and distinguish AGN from
non-AGN components. Slitless spectroscopy with STIS will reveal faint
emission-line sources invisible in our Keck images and will provide spatially-
resolved kinematics, necessary to disentangle the starforming components in
interacting systems. The VLA fields extend over some 8\min\ each, so both
WFPC2 and STIS can be used simultaneously.
================================================================================
Proposal Category: SNAP
Scientific Category: FIELD STELLAR POPULATIONS
ID: 8192
Title: A Snapshot Survey of Probable Nearby Galaxies
PI: Patrick Seitzer
PI Institution: University of Michigan

The census of galaxies in the Local Volume of space is very incomplete,
particularly at the faint end. We propose a snapshot survey to use the high
spatial resolution of HST to determine whether selected galaxies are nearby on
the basis of resolution into stars, and the magnitudes and colors of the
brightest stars. Our sample is chosen from the survey by team members
Karachentsev & Karachentseva (KK98) of some 260 nearby dwarf galaxy
candidates. Our F555W & F814W snapshot survey will concentrate on the 75
candidates most likely to be within 4 Mpc. One HST orbit per galaxy results
in a distance from the magnitude of the tip of the red giant branch (TRGB) and
is sufficiently deep to identify the brightest stellar population. Keck, VLT,
and other large telescopes will be used for spectroscopic follow-up for
abundances and kinematics. As an example of the science to follow from this
survey, consider the incompleteness of the dwarf galaxy census of the Local
Group. Comparisons with the composite luminosity function of nearby groups
indicate that there may be as many as ~ 30 faint Local Group members yet to be
discovered. If only 10\ to be Local Group members, the luminosity function of
the Local Group will no longer appear truncated.
================================================================================
Proposal Category: GO
Scientific Category: AGN HOSTS AND ENVIRONMENT
ID: 8193
Title: Comparing the Hosts of High-z Radio-Quiet Quasars to
Lyman Break Galaxies
PI: Timothy M. Heckman
PI Institution: The Johns Hopkins University

The underlying causes of the rapid cosmological evolution of the quasar
population are a mystery around which are woven many different strands of
contemporary cosmology. Progress on this problem would have important
implications for understanding the early heating of the IGM, the formation and
early evolution of galaxies, and of course the quasar phenomenon itself. We
have begun a program with HST to image the host galaxies of a carefully-
selected sample of five high-z (z ~ 2 to 3) radio-quiet quasars in order to
compare the photometric and structural properties of the host galaxies to
those of the field population of normal star-forming galaxies at similar
redshifts (the `Lyman break' galaxies). We have already obtained deep H-band
NICMOS (rest-frame visible) images of this sample, and find that the host
galaxies are similar to the Lyman break galaxies in terms of their compact
sizes and moderate luminosities. In the present proposal we request time to
obtain WFPC2 images in order to extend this comparison into the crucial rest-
UV spectral window, where the young stellar population can be most directly
probed. This information is essential to begin to understand the long-
hypothesized relationship between quasars and galaxy-building in the early
universe. We emphasize that if the quasar host galaxies have UV sizes and
luminosities similar to typical Lyman break galaxies, we will be able to
detect them.
================================================================================
Proposal Category: GO
Scientific Category: AGN HOSTS AND ENVIRONMENT
ID: 8194
Title: Evolution of high-redshift Seyfert Galaxies
PI: Guenther Hasinger
PI Institution: Astrophysikalisches Institut Potsdam

The ROSAT Deep Survey covers an area of 0.3 deg^2 in the direction of the
Lockman Hole and has found a source density of ~ 1000 deg^-2 with fluxes above
10^-15 cgs. Spectroscopic identifications of optical counterparts at the Keck
telescope are complete to an X-ray flux limit of 2 \cdot 10^-15 cgs and
optical magnitudes of R<23.5^m. Approximately 70\ 0.08 to 4.45. This is the
highest AGN surface density detected in any waveband. The X-ray luminosity
function of AGN shows substantial density evolution, resulting in a
significantly larger space density of low-luminosity AGN (mainly Seyferts) in
the redshift range 1 < z <2, than expected from the conventional pure
luminosity evolution models. We have selected a statistically complete sample
of Seyfert galaxies from the ROSAT Deep Survey. The galaxies have a redshift
range of 0.9--1.9; this is the most distant available Seyfert sample. We
propose to image these objects with broad-band WFPC2 filters in order to
investigate the evolution of their morphology and environments. The
observations will provide insights into the Seyfert phenomenon at intermediate
redshift and will complement similar HST studies of normal galaxies, clusters
and quasars.
================================================================================
Proposal Category: GO
Scientific Category: FIELD STELLAR POPULATIONS
ID: 8195
Title: The Stellar Halo and the Metallicity Distribution
Function in the Giant Elliptical NGC 5128
PI: Gretchen Harris
PI Institution: University of Waterloo

We propose to measure the metallicity distribution function (MDF) of the halo
stars in the nearby (d ~ 3.9Mpc) giant elliptical galaxy NGC 5128 by direct
(V,I) color-magnitude photometry of its old red-giant stars. Because NGC 5128
is 2 magnitudes closer than any other giant E galaxy, it gives us a unique
opportunity to study the enrichment history at a level of detail that is
impossible for any other such galaxy. In a previous highly successful Cycle 5
program, we obtained a deep color-magnitude study of the halo in a field
projected ~eq 21 kpc from the center of NGC 5128, which shows that the MDF is
extremely broad but dominated by an old and metal-rich (Fe/H ~eq -0.6 up to
0.0) stellar population. In Cycle 8, we propose to measure two more fields:
a very remote one at 40 kpc, and a second one in the inner halo at 7 kpc. At
the distance of NGC 5128, the photometric limits of the WFPC2 camera reach
almost 3 magnitudes in I down the red giant branch, allowing the construction
of an accurate MDF. All our target fields are located well away from the dust
lanes and thus not affected by internal reddening or the presence of young
stars. Combined with our Cycle 5 data, these three halo fields will allow us
to study the MDF and metallicity gradient through the halo, and connect these
to enrichment history models.
================================================================================
Proposal Category: GO
Scientific Category: INTERSTELLAR AND INTERGALACTIC MATTER
ID: 8196
Title: High Spatial Resolution UV/Optical Spectroscopy of H II
Regions in the Magellanic Clouds
PI: Donald Garnett
PI Institution: University of Arizona

We propose to obtain high signal/noise UV/optical spectra of several H II
regions in the SMC and LMC with STIS to make definitive measurements of the
abundances of C and N in the Clouds, and to study the temperature, density,
and ionization structures of the nebulae at 10^17 cm resolution. We will
measure gas-phase C/O and N/O ratios from UV emission lines of C III, N III,
and O III, which can provide very reliable abundance determinations. The new
C/O and N/O measurements will be used to address apparent discrepancies
between C and N abundances in the H II regions and those derived in luminous
stars in the Clouds. N III measurements will provide the first reliable N
abundances in the Clouds, and resolve disagreements between optical and IR
abundance determinations. We will look at the magnitude of spatial variations
in C/O and N/O to study the efficiency of mixing of PN ejecta in the ISM.
Measurements of Si III Lambda1883 will yield accurate Si/O ratios and a better
understanding of grain depletions in a variety of environments. Our H II
region sample overlaps that of an ISO IR spectroscopy program, which will
provide complementary information on several ions not observable in the
optical/UV spectrum. High spatial resolution mapping of physical conditions
and ionization will enable us to develop photoionization models of greatly
improved accuracy for the Magellanic Cloud regions.
================================================================================
Proposal Category: GO
Scientific Category: CS
ID: 8197
Title: Detection of ^11B/^10B: Part II
PI: Douglas Duncan
PI Institution: University of Chicago

HST observations (e.g. Duncan Etal 1992; 1997) have led to new theories of how
cosmic rays (CRs) rich in CNO near massive stars form the light elements Li,
Be, and B (e.g. Ramaty Etal 1996, 1998). The neutrino process in SN, which
has never been experimentally verified, should also produce boron, but only
^11B, yielding a very different isotopic ratio than CR spallation. The boron
isotope ratio, \bele/\bten, can provide a definitive test of both these
theories, but its galactic evolution is completely unknown. Our previous GHRS
echelle observation of the moderately metal-poor (Fe/H=-1.0) star HD76932
placed a limit on its B isotope ratio, but not a definite value, because
possible blending from an unknown spectrum line could not be ruled out (Rebull
Etal 1998). The discovery of a halo star greatly depleted in B (Primas Etal
1998b) provides a wonderful opportunity to make the result definite. By
comparing two similar (Fe/H ~ -1.6) stars, which have very different amounts
of B, we can rule out or measure any blends. This should give a definite
result for \bele/\bten\ at metallcity Fe/H ~ -1.6, an epoch when massive star
SN should have dominated galactic nucleosynthesis. Furthermore, we can then
use our blending knowledge to reanalyze HD76932, getting a definite result for
its \bele/\bten\ ratio as well.
================================================================================
Proposal Category: GO
Scientific Category: INTERSTELLAR AND INTERGALACTIC MATTER
ID: 8198
Title: Understanding the Starburst-like Dust in the Small
Magellanic Cloud
PI: Karl Gordon
PI Institution: Louisiana State University

The similarities between the ultraviolet extinction found in the star forming
bar of the Small Magellanic Cloud (SMC) and starburst galaxies has highlighted
the importance of understanding the dust extinction in the SMC. The behavior
of the UV extinction in the SMC is unlike that seen in any other Local Group
galaxy. In a recent study, it was shown that the traditional (no 2175
Angstrom\ bump, high far-UV rise) SMC extinction curve is seen in the SMC's
star forming bar, while outside of this bar a much more Galactic (2175
Angstrom\ bump, weaker far-UV rise) extinction curve is seen. These results
are tentative due to the fact that only four extinction curves are known with
certainty in the entire SMC. We propose to determine the ultraviolet
extinction curves toward three additional stars stars in the SMC. These
sightlines were chosen to be located near differing levels of star formation
activity. In addition to helping understand the origin of the UV dust
extinction in starburst galaxies, study of the spatial variation of UV
extinction in the SMC also holds the promise of helping to understand the
origin of the 2175 Angstrom\ bump. Understanding the behavior of dust in
starburst regions is important as the differences between the extinction
corrections for the Milky Way and the SMC is a factor of 10 at 1500 Angstrom.
================================================================================
Proposal Category: GO
Scientific Category: CLUSTERS, LENSING AND COSMOLOGY
ID: 8199
Title: Local Cosmology: The Nearby Flow Field and its Structure
PI: Marc Davis
PI Institution: University of California

It is a curious fact that very little data are available to constrain the
velocity field of galaxies in the local neighborhood (<= 500 km/sec).
Although tremendous progress has been made in recent years in mapping the
large-scale gravitational field (out to scales of cz ~ 10,000
km/sec), the major impediment to constraining the local flow is the lack
of a consistent set of distances to nearby galaxies. Locally the
deviations from a pure Hubble flow have been predicted to be large and
measurable, as much as 1 magnitude(
================================================================================
Proposal Category: GO
Scientific Category: GALAXY POPULATIONS AND INTERACTIONS
ID: 8200
Title: Globular Cluster Systems in Three Giant Coma Ellipticals
PI: William Harris
PI Institution: McMaster University

In our previous imaging programs in Cycles 4 and 5, we have investigated the
luminosity functions, metallicities, and specific frequencies of the globular
cluster systems in three Coma giant ellipticals: the central cD NGC 4874, and
two normal giants NGC 4881 and IC 4051. These three have turned out to be
surprisingly and sharply different in globular cluster specific frequency,
metallicity distribution, and spatial structure. In certain cases, they
display a unique combination of factors which we have seen in no other
galaxies (such as extremely high specific frequency in a normal and non-
central cluster elliptical; distinctly unimodal metallicity distributions; or
enormously large core radius). These Coma ellipticals present serious
challenges to virtually every one of the current formation scenarios for
globular cluster systems. Coma is the densest and richest cluster of galaxies
in which globular cluster populations lie within reach of the HST cameras. We
propose to investigate this rich proving ground further by deep V,I WFPC2
imaging of three more of its giant ellipticals: the central (non-cD)
supergiant NGC 4889, the outlying cD NGC 4839, and another normal luminous gE
in the core region, NGC 4926. These targets will considerably extend the
range of parameter space that we have sampled in the systematics of globular
cluster populations.
================================================================================
Proposal Category: GO
Scientific Category: GALAXY POPULATIONS AND INTERACTIONS
ID: 8201
Title: The Ultraviolet Properties of Ultra-Luminous Infrared
Galaxies
PI: Gerhardt R. Meurer
PI Institution: The Johns Hopkins University

Ultraluminous Infrared Galaxies (ULIRGs) are the most luminous galaxies known
in the local universe, and are predominantly powered by massive star
formation. ULIRGs are the only type of star forming galaxies in the local
universe with bolometric luminosities approaching those of the Lyman-dropout
systems and SCUBA sub-mm detections at z~ 3. However, very few observations
of ULIRGs exist at ultraviolet (UV) wavelengths to compare to these high-z
detections. Here we propose imaging a modest size sample of ULIRGs in the UV
with STIS. This will extend the observations of these objects into the
wavelength range where massive stars dominate the intrinsic spectrum. We will
then be better able to compare the rest-frame UV morphology and overall SEDs
of ULIRGs to the high-z systems. We will test whether transmitted UV light
traces star formation and whether the UV SED reddens with dust absorption as
is the case for UV selected starbursts. We will assess what impact ULIRGs
make on rest-frame UV surveys of galaxies. Our images combined with archival
optical to near IR images will build on the HST heritage allowing key issues
concerning the physics of ULIRGs to be addressed. These include the relative
importance of clustered versus diffuse star formation, the mechanism of star
formation feedback, and whether and how UV light escapes these dusty systems.
================================================================================
Proposal Category: SNAP
Scientific Category: CLUSTERS, LENSING AND COSMOLOGY
ID: 8202
Title: Bright Quasar Close Lensing Search
PI: Michael Gregg
PI Institution: University of California, Davis

We propose a second generation snapshot survey of bright quasars, optimized to
find lenses with component image separations < 1". Most models of the lens
components predict distributions which peak at separations in the range 0arcs5
to 1", yet the observed distribution of lenses peaks at 1arcs3. The lack of
observed systems with close separations is difficult to reconcile with a
geometrically flat universe, preferred by theory (inflation) and the
observational determinations of the cosmological constant from type Ia
supernovae. The survey will improve over the earlier pre-refurbishment
snapshot survey of quasars (Bahcall et al.\ 1992; Maoz et al.\ 1993) in two
important respects. With the restored PSF, new images will be considerably
more sensitive to the presence of both close separation and faint lens
components, and because STIS reaches 2 magnitudes fainter than the PC, the
snapshot images can be kept to short exposures, containing the typical
trailing under gyroscopic guiding to less than a pixel (<0arcs05).
================================================================================
Proposal Category: GO
Scientific Category: GALAXY POPULATIONS AND INTERACTIONS
ID: 8203
Title: Dwarf busting in Abell 868
PI: Simon Driver
PI Institution: University of St Andrews

We request 24 orbits to obtain a deep mosaic (6 * 4-orbit pointings) of the
central region of A868, a rich Abell cluster which we have imaged
comprehensively from the ground. The objective is to identify and characterise
the morphological nature of the dwarf galaxy population(s) responsible for
the steep upturn seen in this cluster's luminosity function. While similar
upturns have been reported in many clusters, the specifics of the dwarf
population remain unknown as these objects cannot be resolved from the ground.
What type of dwarf galaxies are they ? Is there more than one population
contributing ? How are they clustered ? By obtaining deep high-resolution HST
WFPC2 imaging over a central strip of 7.5' * 3.75' we will be able to measure
morphologies, light-profiles and the clustering properties of the dwarf
population(s) down to M_I = -16 mags (H_o=75kms^-1Mpc^-1). Although we shall
primarily concentrate on the dwarf galaxies, we will also recover the
cluster's morphological luminosity distributions for elliptical, spirals and
irregulars over a broad absolute magnitude range (-24 < M_I < -16 mags) as
well as the more quantitative bivariate brightness distribution (-24 < M_I < -
16 mags, 17.0 < mu_e^I < 25 mags per sq arcsec). Comparing these results to
those recently derived for the general field will provide an insight into the
environmental influences on morphology and surface brightness.
================================================================================
Proposal Category: GO
Scientific Category: HOT STARS
ID: 8204
Title: Calibration of the Wind Momentum--Luminosity Relationship
in Cyg OB2
PI: Artemio Herrero
PI Institution: Instituto de Astrof'\isica de Canarias

We propose to improve the calibration of the Wind momentum -- Luminosity
Relationship of hot stars at solar metallicity by adding new objects with
well determined distances, stellar parameters and wind momenta. We propose to
acquire STIS low-resolution FUV spectra of O- and B-supergiants belonging to
the same OB association to determine their terminal wind velocities. We
selected stars in Cyg OB2, for which we alredy have optical observations and
have performed analyses (or which are currently under way) with our model
atmospheres codes to determine their stellar parameters and mass loss rates. A
precise calibration of the WLR using objects of the solar neighbourhood is
crucial for future applications of the method to determine extragalactic
distances out the Virgo and Fornax clusters of galaxies.
================================================================================
Proposal Category: GO
Scientific Category: YOUNG STARS AND CIRCUMSTELLAR MATERIAL
ID: 8205
Title: UV Spectroscopy of Infalling Cometary Material in Solar-
Type Pre-Main Sequence Stars
PI: Carol Grady
PI Institution: National Optical Astronomy Observatories, STIS Group

Models for the formation of the Solar System predict that an intermediate
stage in planet formation was the assembly of material in the disk into
planetesimals, and that this should be a common step in the evolution of
planetary systems. Planetesimals are difficult to detect directly except by
activity in renewing the small grain population in mature (e.g. t>100 Myr)
planetary disks, or by the presence of cometary activity. Cometary activity
can provide a marker for the presence of planetesimals in younger systems
where much of the dust is a remnant of the original protoplanetary disk. The
presence of such cometary activity has been inferred from redshifted
absorption features in the optical & UV spectra of Beta Pic and a large number
of younger, intermediate-mass pre-Main Sequence stars. However, if the
interpretation of these features as the aggregate comae of swarms of star-
grazing bodies is correct, similar activity must be present and remotely
detectable in the disks of young, solar analogs. We propose using HST STIS to
obtain the first UV spectroscopic observations of infall activity in the disks
of young, Solar-type stars, supplemented by a comparison intermediate- mass
star. The data will be used to determine whether infall activity around young
Suns evolves on the same time scale as for disks around more massive and
luminous stars.
================================================================================
Proposal Category: GO
Scientific Category: YOUNG STARS AND CIRCUMSTELLAR MATERIAL
ID: 8206
Title: The Structure of the Accretion Flow on pre-main-sequence
stars
PI: Erik Gullbring
PI Institution: Stockholm Observatory

We propose to test an essential prediction of the magnetospheric accretion
model for T Tauri stars. STIS echelle spectra will be used to search for the
relatively narrow high-temperature emission lines that must result from the
magnetospheric accretion shock, but are not expected in the previous,
alternative boundary layer model. By combining the results from high
temperature (10^5 K) lines, accessible only with HST, with optical lines and
optical-UV continuum emission, we will develop physically self-consistent
models of accretion shock structure. The geometrically distribution of the
emitting gas as derived from our results will test theories of mass-loading of
magnetic field lines at the magnetosphere-disk interface. Analysis of the UV
emission lines will also provide improved calibrations between ultraviolet
continuum emission and accretion luminosities, and thus improve estimates of
mass accretion rates for T Tauri stars.
================================================================================
Proposal Category: GO
Scientific Category: HOT STARS
ID: 8207
Title: The Ofpe/WN stars in M33: understanding Wolf-Rayet star
formation in different environments
PI: Luciana Bianchi
PI Institution: The Johns Hopkins University

We propose to obtain STIS Ultraviolet spectra of seven Ofpe/WN9 stars
(``slash stars'') in M 33 discovered from ground-based (KPNO, MMT)
classification spectra of the 400 UV-brightest stellar sources measured in the
Ultraviolet Imaging Telescope images (Massey, Bianchi, Hutchings & Stecher
1996). The purpose is to derive stellar parameters (T_eff, Luminosity, Radius,
Mass, element abundances, mass-loss rate, and wind velocity) by modeling wind
and photospheric line profiles. The measured stellar quantities will be
compared (a) with our previous HST observations of O supergiants and WNL stars
in M33, and (b) with archive spectra of Ofpe/WN9 stars in the Galaxy and the
LMC. The program will provide constraints on the evolutionary scenarios for
Ofpe/WN9 interpretations, clarify on the formation of Wolf-Rayet stars, and
will extend our comparison of massive populations in Local Group galaxies to
another, important class of objects. WFPC2 imaging parallel to the primary
spectroscopy in UBV and FUV filters will allow to substantially extend our
study of the hot massive star population and populous stellar clusters in this
galaxy.
================================================================================
Proposal Category: GO
Scientific Category: GALAXY POPULATIONS AND INTERACTIONS
ID: 8208
Title: Galaxy Interactions, Tidal Debris, and the Origin of
Intracluster Light in the Coma Cluster
PI: Michael Gregg
PI Institution: University of California, Davis

We propose to obtain deep WFPC2 and parallel STIS images of three extended,
low surface brightness objects that we have recently discovered in the Coma
cluster; these objects are tidal debris being stripped from galaxies and added
to the general cluster background. These images will enable direct study of
the brightest blue and red supergiants, globular clusters, and star forming
regions which may be present, or will place strong limits on the numbers of
such objects and any recent star formation. We also propose similar
observations of two spirals in the core of Coma: both are losing their ISM to
the hot cluster gas and one is the source of one of the low surface brightness
tidal features. By imaging these galaxies, we will get a high resolution look
at the interaction between the cluster and interstellar media, as well as any
ram-pressure induced star formation. The tidal features in Coma appear to be
adding material to the background light and cD galaxy envelopes at a
significant rate; determining the nature of the added stellar population and
the interactions which produce it are critical to understanding the formation
and evolution of cD galaxies and clusters.
================================================================================
Proposal Category: GO
Scientific Category: BINARY STARS
ID: 8209
Title: The Complex Circumstellar Environment of the Massive
Contact Binary RY Scuti
PI: Robert D. Gehrz
PI Institution: University of Minnesota

RY Scuti is a very massive and luminous evolved contact binary system. The
combined luminosity of the stellar components is near the Eddington limit,
resulting in complex, time variable mass-loss and mass-transfer in the
system's common envelope. It is surrounded by an unusual nebula that is only
a few arcseconds in extent. Our previous ground-based infrared observations
have shown a compact dust torus in the equatorial plane of the system. Our
recent HST/WFPC2 images have revealed a set of ionized rings at the inner edge
of this dust torus, as well as several other complex structures within 1" of
the star. We propose to obtain STIS spectra that will spatially resolve the
spectrum of the star from its compact nebula for the first time. This will
allow us to investigate the complex mass loss winds responsible for the
formation of the nebula. We also propose to duplicate our successful HAlpha
images in order to investigate possible variability of the nebula resulting
from eclipses in the binary system. Finally, we propose to image RY Scuti in
SIII, which will probe the excitation conditions in the nebula when compared
with our HAlpha image.
================================================================================
Proposal Category: GO
Scientific Category: STELLAR EJECTA
ID: 8210
Title: HST Imaging of Bipolar Proto-Planetary Nebulae and
Circumstellar Arcs
PI: Bruce Hrivnak
PI Institution: Valparaiso University

Proto-planetary nebulae (PPN) provide the best opportunity to test theories of
asymptotic giant branch mass loss (symmetric/asymmetric, continuous/episodic)
and the processes which shape planetary nebulae. These remain among the
outstanding unsolved problems in stellar evolution. We propose to use WFPC2 to
observe several new PPN which display evidence of being bipolar, to study this
phenomena. These will be modeled using our newly-developed axially-symmetric,
2-D, dust, radiation-transfer code. We have previously used WFPC2 to image 4
new bipolar PPN, and have successfully modeled their structures and spectral
energy distributions. This proposal will extend this study to additional PPN
and give important evidence on how common is the bipolar structure. In
addition, we have found concentric arcs, seen previously in the Egg Nebula, to
exist in 2 additional bipolar PPN. This has important implications for the
mass loss mechanism. We will investigate the existance of these arcs in
additional bipolar PPN by obtaining deep images.
================================================================================
Proposal Category: GO
Scientific Category: BINARY STARS
ID: 8211
Title: An Ultraviolet Census of Counterparts to Highly Luminous
X-ray Sources in M31 Globular Clusters
PI: Bruce Margon
PI Institution: University of Washington

The cores of certain globular clusters in our Galaxy contain some of the most
extraordinary stars known, identified by their intense, near-Eddington limited
X-ray emission. Essentially all are X-ray bursters, emitting L_x>10^4 L_\odot
in a few seconds. At least one, and probably two, of these sources are the
shortest binary period stars known anywhere: NGC 6624 contains a double-
degenerate binary with an 11 minute orbital period. HST has enabled the
optical identification and study of counterparts to a half-dozen of these
sources in the Milky Way, but the systems prove to have a wide range of
optical luminosities and orbital periods, with few obvious patterns emerging.
However, one common characteristic of these sources is intense flux at 1400
Angstrom, a wavelength where the 10^5 cluster stars virtually disappear. The
Andromeda Nebula is known to contain dozens of bright globular cluster X-ray
sources. We propose here a modest, first imaging reconnaissance of globular
cluster X-ray source counterparts in M 31 at 1400 Angstrom, with a goal of
materially increasing the number of X-ray clusters with counterparts, and
further exploring an odd dispersion of L_X/L_1400 seen in galactic clusters.
================================================================================
Proposal Category: GO
Scientific Category: CLUSTERS, LENSING AND COSMOLOGY
ID: 8212
Title: Reconciling the SBF and SNIa Distance Scales
PI: Edward A. Ajhar
PI Institution: National Optical Astronomy Observatories

We propose to use WFPC2 to measure surface brightness fluctuation (SBF)
distances to host galaxies of well-measured type Ia supernovae (SNIa) in order
to resolve the discrepancy between H_0 values determined from the SBF
distances and from SNIa distances. Currently, SBF distances yield H_0 ~
80kmsMpc, and SNIa distances yield H_0 ~ 60. While both of these distance
estimators provide excellent internal error consistency (near 5\ systematic
errors are preventing these methods from providing consistent values for the
Hubble parameter. Given that there are so few reliable methods for
determining distances over large ranges, it is imperative that we understand
the discrepancy between the SBF and SNIa methods. Only then can these methods
converge on the true value of H_0.
================================================================================
Proposal Category: GO
Scientific Category: GALAXY POPULATIONS AND INTERACTIONS
ID: 8213
Title: Globular Clusters of Low Surface Brightness Galaxies
PI: Bryan Miller
PI Institution: Leiden Observatory

We propose to investigate globular cluster (GC) systems in giant low surface
brightness (LSB) galaxies. The primary goals of the project are to determine
the number of GCs in two nearby LSB galaxies and to estimate their ages. LSB
spirals tend to be more isolated, more gas rich, and have had more quiescent
star formation than their high surface brightness (HSB) cousins. LSB galaxies
have either been forming stars very slowly for a Hubble time or have formed
within the last few Gyr. Thus, their star formation histories may be very
different from those of HSB galaxies. We will use the ages of the GCs to
estimate the cluster formation histories of LSBs. The colors and magnitudes
of their GCs will allow us to date the clusters and put constraints on when
the galaxies started to form. Thus, we may be able to distinguish whether
they are very slowly evolving or very young. We will also compare the
specific globular cluster frequency (number per unit luminosity) and the shape
of the GC luminosity function in LSBs with those quantities for GCs in HSB
spirals. The results of this project will have important implications for
galaxy and GC formation.
================================================================================
Proposal Category: GO
Scientific Category: GALAXY POPULATIONS AND INTERACTIONS
ID: 8214
Title: The Evolution of Globular Cluster Systems In Early Type
Galaxies
PI: Carl Grillmair
PI Institution: SIRTF Science Center

We will measure structural parameters (core radii and concentrations) of
globular clusters in four early-type galaxies using deep, four-point dithered
observations. We have chosen globular cluster systems which have young,
intermediate age, and old cluster populations, as indicated by cluster colors
and luminosities. Our primary goal is to test the hypothesis that globular
cluster luminosity functions evolve towards a ``universal'' form. Previous
observations have shown that young cluster systems have exponential luminosity
functions rather than the characteristic log-normal luminosity function of old
cluster systems. We will test to see whether these young systems exhibit a
wider range of structural parameters than old systems, and whether and at what
rate plausible disruption mechanisms will cause the luminosity functions to
evolve towards a log-normal form. A simple observational comparison of
structural parameters between different age cluster populations and between
different sub-populations within the same galaxy will also provide clues
concerning both the formation and destruction mechanisms of star clusters, the
distinction between open and globular clusters, and the advisability of using
globular cluster luminosity functions as distance indicators.
================================================================================
Proposal Category: GO
Scientific Category: STELLAR EJECTA
ID: 8215
Title: New clues to the ejection process in young stars:,
Forbidden line imaging of T Tauri micro-jets
PI: Catherine Dougados
PI Institution: Laboratoire d'Astrophysique, Observatoire de Grenoble

Bipolar outflows play a fundamental role in star formation. However, the
ejection and collimation mechanisms are still not identified. Classical T
Tauri stars (CTTS) offer a unique opportunity to progress on this problem, as
their optical forbidden line emission allows to trace collimated winds very
close to the central star (d <= 100 AU). Determining the exact flow geometry
and the line excitation mechanism is essential to obtain new clues to the mass
-loss process in young stars. Our team has recently obtained at CFHT the first
sub-arcsecond resolution (FWHM=0.15") images of micro-jets around 3 T Tauri
stars: DISTANT GALAXIES Tau, CW Tau, RW Aur. They reveal unprecedented details about the
morphology of these jets, strongly suggesting ejection and velocity
variability. However, such ground-based studies are limited to high-accretion
sources. We propose here to use the unique HST resolution capabilities to
image for the first time the innermost regions of jets associated with 4 CTTs
with R band magnitudes > 13. Extending our sample to less extreme stars is
crucial if we want to derive meaningful constraints on the mass-loss process
in CTTS. Images in the 3 narrow-band filters S ii, H_Alpha or N ii and O
i and in the adjacent continuum will be obtained. We will thus have access
both to the jet excitation conditions and intrinsic morphology, and compare
them with theoretical predictions from MHD models.
================================================================================
Proposal Category: SNAP
Scientific Category: YOUNG STARS AND CIRCUMSTELLAR MATERIAL
ID: 8216
Title: T Tauri Star Snapshot Survey II. Completing the CTTs
Sample
PI: Karl Stapelfeldt
PI Institution: Jet Propulsion Laboratory

Infrared and millimeter continuum photometry suggests that as many as 50\
solar nebula from which our planetary system formed. However, high
resolution, high dynamic range optical images currently exist for only a few
dozen of the hundreds of nearby T Tauri stars that may harbor observable
disks. Initial HST imaging with WFPC2 has shown that circumstellar disks are
detectable as reflection nebulosities adjacent to the bright PSF of the
central star. We propose a continuation of our R-band SNAPshot survey of T
Tauri stars in the five nearest star-forming clouds. The expanded source list
includes all nearby classical T Tauri stars with HAlpha equivalent widths
greater than 30 Angstrom\ - a group of objects which theory suggests are
actively accreting material from circumstellar disks. Our goals are to
determine the frequency of disk detections, to measure the disk sizes and
constrain their masses, to identify the nearly edge-on systems which are
particularly favorable for studies of disk geometry, and to discover new disks
undetectable using other techniques. In combination with our Cycle 7 program,
the result will be a large, uniform image database on as many as 140 young
stars likely to possess circumstellar disks. This database will be of
fundamental importance to understanding the nature of planet-forming
environments and their frequency in the galaxy.
================================================================================
Proposal Category: GO
Scientific Category: HOT STARS
ID: 8217
Title: Tests of Stellar Models Using Four Extremely Massive
Spectroscopic Binaries in the R136 Cluster
PI: Philip Massey
PI Institution: National Optical Astronomy Observatories

We are proposing to observe four non-interacting double-lined spectroscopic
binaries discovered in the R136 cluster by our Cycle 6 FOS spectroscopy
(Massey & Hunter 1998, ApJ, 493, 180). These binaries are all of very early
type (O3-4 + O3-8) and should prove to be of very high mass. These data will
allow us to extend the empirical mass-luminosity relation to higher masses,
providing crucial checks on stellar interior and atmosphere models.
Examination of the WFPC2 archives reveals that at least three of the four
systems undergo eclipses. We plan to obtain simultaneous spectroscopy and
photometry for all four systems during a single 2-orbit visit. Fourteen such
visits, over an interval of a few weeks, should provide direct measurements
for the masses of eight of the highest mass stars ever analyzed.
================================================================================
Proposal Category: GO
Scientific Category: SOLAR SYSTEM
ID: 8218
Title: Exploring Triton in the Act of Global Change
PI: Alan Stern
PI Institution: Southwest Research Institute

Triton appears to be undergoing the start of a long-awaited, and perhaps
fundamental, global seasonal change. As a result of this change, seasonally
deposited ices should sublime into the atmosphere, revealing extensive areas
of the more permanent underlying surface, most likely with different
photometric properties. We propose a 6-orbit Cycle 8 program consisting of
STIS mid-UV spectroscopy and VIS/mid-UV imaging in order to better quantify
the changes now underway, and to provide a critical benchmark for Triton's
photometric state before still more time elapses. HST is required for this
work owing to Triton's small (0.13") apparent diameter and the need for UV
observations.
================================================================================
Proposal Category: GO
Scientific Category: BINARY STARS
ID: 8219
Title: A Definitive Census of the Cataclysmic Variable
Population in 47 Tuc
PI: Christian Knigge
PI Institution: Space Telescope Science Institute

We propose to carry out a deep, far-ultraviolet (FUV), time-resolved,
spectroscopic search for faint cataclysmic variables (CVs) in the globular
cluster (GC) 47 Tuc. We will use STIS to carry out FUV slitless spectroscopy
and imaging of this cluster at 6 epochs for a total of 30 HST orbits. Since
crowding is not a problem in the FUV, this will yield time-resolved spectra
and photometry of all UV-bright objects in the cluster core. Our CV census
will be both deep enough to be essentially complete M_V(limit) ~eq 11
spectroscopically and ~eq 13 photometrically and ``broad'' enough to involve
all of the following CV characteristics:, (1) UV brightness;, (2)
blue FUV spectral shape;, (3) strong C iv 1550 Angstrom emission;,
(4) He ii 1640 Angstrom emission (especially in magnetic systems);, (5)
short time-scale (~ minutes) variability (flickering, WD spin);, (6)
intermediate time-scale (~ hours) variability (orbital variations);, (7)
long time-scale (~ weeks) variability (dwarf nova eruptions)., Tidal capture
theory predicts that we should discover 40 CVs in 47 Tuc and spectroscopically
confirm 25. These numbers are large enough to allow the first definitive test
of the theory.
================================================================================
Proposal Category: GO
Scientific Category: CLUSTERS, LENSING AND COSMOLOGY
ID: 8220
Title: Galaxy M/L Ratios, the Morphology-Density Relation, and
Weak Lensing in the z=1 Cluster of 3C184
PI: Marijn Franx
PI Institution: Leiden Observatory

We propose to obtain a deep mosaic of WFPC2 images for the radio selected
cluster around 3C184 at z=0.996. This proposal is the last part of a program
to take large HST WFPC2 mosaics of distant clusters. We augment the HST
mosaics of the clusters with extensive ground-based spectroscopy and imaging
from the Keck, MMT, ESO-VLT, NTT, and WHT telescopes. The large areal coverage
in high-z clusters is essential for studying the whole cluster population, and
for determining radial gradients in their properties. We have the following
scientific goals: (i) Use the Fundamental Plane of early-type galaxies to
measure the evolution of M/L ratios out to z=1, putting strong constraints on
the (star) formation epoch of early-type galaxies. (ii) Determine the density-
morphology relation at z=1, and its evolution from z=0 to z=1. The radial
distributions of starburst and post-starburst galaxies, as well as galaxy
mergers, will be of particular interest. (iii) Use weak lensing to derive the
detailed mass distribution of the cluster. 3C184 is well suited because it is
a massive, high redshift cluster, with a measured velocity dispersion. It will
provide great leverage on galactic evolutionary studies because of its high
redshift. The fully processed mosaic of this cluster, covering 5*5 arcmin
(1.5times1.5h^-2 Mpc), will be made available to the astronomical community,
with our other cluster mosaics at z=0.33, 0.58, and 0.83.
================================================================================
Proposal Category: GO
Scientific Category: STELLAR EJECTA
ID: 8221
Title: The next bright Galactic nova: High Resolution Imaging
PI: Michael Shara
PI Institution: Space Telescope Science Institute

The recurrent nova T Pyxidis is one of only ~20 novae with known shells, and
the only recurrent nova with clearly resolved circumstellar matter. A unique
and once-in-a-generation opportunity will exist during T Pyxidis' next
eruption (now overdue) to determine: 1) The uniformity and isotropy of
material (both dust and different chemical elements) ejected in previous
eruptions, and 2) The smallest structures formed in nova eruptions. We propose
to use WFPC2 to image T Pyx after it erupts to search for fluorescence and
reflection light echoes from, and small-scale structure in, the nova
circumstellar gas and dust ejecta. Only two novae are presently known to have
a highly structured shell that can be defined as ``very'' clumpy. These novae
are GK Per (known from the ground) and T Pyx (HST cycle 4 WFPC2 images). It's
unclear if this structure is common to all nova shells or, if it is, how the
structure is created. Though T Pyx is ``overdue'' it may take several years
before it goes off again. We therefore propose to use the TOO time, if
allocated, to follow the eruption of the next bright Galactic nova with WFPC2
(if T Pyx does not erupt) to determine how quickly the ejecta of a nova become
clumpy.
================================================================================
Proposal Category: GO
Scientific Category: STELLAR EJECTA
ID: 8222
Title: An Emission Line Survey of the Crab Nebula
PI: Jeff Hester
PI Institution: Arizona State University

We propose to conduct a WFPC2 survey of the Crab Nebula in the light of
emission from O I, S II, and O III, and in a single continuum band. WFPC2
observations have already dramatically reshaped our understanding of the Crab.
They have shown that the filaments in the Crab are the result of Rayleigh-
Taylor instabilities at the surface of the synchrotron nebula. These data
also provide the first direct evidence of the existence of an extended remnant
of freely expanding ejecta that surrounds the visible nebula and into which
the synchrotron nebula is expanding. High spatial resolution observations of
the range of conditions around the R-T unstable interface are needed if we are
to develop this understanding further or apply it to questions of the overall
structure and evolution of the remnant. We have also found that the
subarcsecond structure of filaments strongly influences overall filament
spectra. Detailed knowledge of the ionization structure of filaments at HST
resolution is essential to interpret any spectroscopic observations of the
Crab, and is needed in particular if we are to disentangle such structural
effects from the spatial abundance distribution within the nebula. In
addition to our specific scientific objectives, this survey will provide a
data set that is essential to all future studies of the structure, dynamics,
and evolution of the Crab.
================================================================================
Proposal Category: GO
Scientific Category: AGN HOSTS AND ENVIRONMENT
ID: 8223
Title: The nature of radio--optical alignments in faint radio
sources
PI: Mark Lacy
PI Institution: University of Oxford

Study of the host galaxies of high redshift AGN is important if we are to
attempt to investigate the population of high redshift galaxies which are not
selected on the basis of luminous starburst activity. However, it is first
important to establish how much the AGN affects the observed properties of the
host galaxies even in samples of relatively weak AGN. We propose to use
objects from a flux-limited sample of 7C radio sources, one of the first
complete samples of radio sources with a flux limit more than an order of
magnitude fainter than 3C, to study the effects of weaker radio-loud AGN and
their jets on the host galaxies of radio sources at z~ 1. This will complement
studies already made or in progress of the much more radio-luminous 3C and 6C
objects, and in particular we will be able to make a direct comparison with
the 3C sample of Ridgway & Stockton (1997). Results from our ground-based
study indicate that the alignment effect is still present in the 7C sample at
z~ 0.7, but is probably weaker and on a smaller spatial scale than that in 3C.
With HST data we can investigate the z~ 1 regime at high spatial resolution,
and compare galaxies and quasars directly.
================================================================================
Proposal Category: GO
Scientific Category: SOLAR SYSTEM
ID: 8224
Title: UV Imaging of Europa & Ganymede: Unveiling Satellite
Aurora & Electrodynamical Interactions
PI: Melissa McGrath
PI Institution: Space Telescope Science Institute

We propose to obtain ultraviolet images of Europa and Ganymede using STIS,
with suitable filters to isolate atomic oxygen (1304 and 1356 Angstrom ) and
hydrogen (Lyman-Alpha) emissions, to study the interaction of the Jovian
magnetosphere with the tenuous oxygen atmospheres of these icy satellites.
Previous spectroscopic observations, from both HST (with GHRS) and Galileo,
suggest the presence of polar aurorae on Ganymede whose geometry would be
clearly delineated in these images. Europa is expected to show an oxygen
emission morphology similar to that recently discovered on Io.
================================================================================
Proposal Category: GO
Scientific Category: AGN PHYSICS
ID: 8225
Title: Absorption and obscuration in radio-loud quasars
PI: Joanne Baker
PI Institution: University of California, Berkeley

The role of associated absorption systems and dust obscuration close to the
central engines of AGN is not understood. Using the low-frequency selected
Molonglo Quasar Sample, we have discovered evidence for direct links between
obscuration/absorption and the radio properties of quasars that shed new light
on the physics of radio source evolution. To establish these results
unequivocally, we require near-UV spectroscopy with STIS on the HST of a
complete set of 19 Molonglo quasars with 0.7 observe the restframe spectral region that includes Ly-alpha\ and C IV. To
detect reddening, we will measure UV--optical continuum slopes and Ly-
alpha/\hb\ line ratios and will also search for absorption systems close to
the quasar redshift. These properties will be investigated as a function of
redshift, orientation and radio source size in order to test basic models for
dust obscuration near the central engines of AGN and also the physics of radio
-source expansion.
================================================================================
Proposal Category: GO
Scientific Category: HOT STARS
ID: 8226
Title: Discerning the Origins of Blue Stragglers: Masses and
Rotation Rates
PI: Michael Shara
PI Institution: Space Telescope Science Institute

Conventional wisdom holds that the masses of Blue Straggler Stars (BSS) in
globular clusters (GCs) are significantly larger than the turnoff mass. We
have, for the first time, supported this theoretical claim by directly
measuring the mass of the blue straggler BSS--19 in the core of 47 Tuc to be M
= 1.7 +/- 0.4 M(sun), nearly twice that of the oldest core-hydrogen burning
cluster star (Shara et al. 1997, ApJ, 489, L59). Observations reveal that the
BSS in Galactic open clusters have low rotation velocities. However, we also
have found that BSS--19 is rotating rapidly, with a measured projected
rotation velocity v \sin i = 155 +/- 55 kms. We propose to obtain STIS
spectroscopy of 20 BSS in each of the GCs 47 Tuc, M 3, and NGC 6752, in order
to measure accurate masses and rotation rates. The mass distributions will
test the most basic assumption about BSS, namely, that massive stars with
lifetimes <= 10^9 yr are continuously forming (probably by coalescence) in the
oldest (\gta 10^10 yr) objects in the universe. Together, the mass and
rotation velocity distributions will distinguish between collisional and close
binary coalescence scenarios. Our proposed observations will definitively
constrain theories of BSS formation in GCs.
================================================================================
Proposal Category: GO
Scientific Category: BINARY STARS
ID: 8227
Title: The Shock Cones and Underlying Stars in Interacting Wolf-
Rayet Binaries
PI: Michael Shara
PI Institution: Space Telescope Science Institute

We are proposing STIS longslit spectroscopy of 3 HST-resolved Wolf-Rayet
binary stars. Our HST/WFPC2 Cycle 6 and 7 SNAP proposals clearly resolve these
3 Wolf-Rayet (WR) stars with previously suspected or debated companions. From
ground-based radio data, two of these WR stars are also known to be strong
emitters of non-thermal radiation. Our 1998 Astronomical Journal paper
conclusively linked these two traits, demonstrating the coincidence of
location of the non-thermal emission with the wind interaction region (bow
shock head) between each pair. STIS spectra will provide clear determinations
of the natures of each of the components of these 3 close WR binaries, and
possibly, their wind collision regions.
================================================================================
Proposal Category: GO
Scientific Category: GALAXY STRUCTURE AND DYNAMICS
ID: 8228
Title: The black hole versus bulge mass relationship in spiral
galaxies
PI: David Axon
PI Institution: University of Manchester

We propose to obtain long-slit spectroscopic observations with STIS of the
ionized disk gas in a volume limited sample of 54 nearby spirals, for which we
already have ground based emission line rotation curves, CCD surface
photometry and radio maps. For each galaxy we will use the G750M grating to
measure the HAlpha rotation curve in three different locations (a central
0arcs1 wide slit and two parallel 0arcs2 wide slits offset by ~eq0arcs2). We
will use these observations to determine if the gas motions and line-profiles
match those of a thin disk in Keplerian motion. Our strategy of securing data
along three parallel slits yields kinematic constraints on the center of mass,
inclination angle and line-of-nodes that are independent of photometric
constraints. This greatly improves the robustness of our estimates compared to
single slit measurements. Our observations will enable us to measure the mass
within a radius of ~eq7-14pc. Detailed simulations show that any black hole or
mass concentration >~ 10^7 M_\odot will be confidently detected. Even for the
most distant and most massive bulges we should either detect a black hole or
derive a meaningful upper-bound. In combination with our acquisition images of
the central ~5", our results will for the first time establish the black hole
mass distribution and its relationship to bulge mass/luminosity and cusp-slope
in a significant number of local spiral galaxies.
================================================================================
Proposal Category: GO
Scientific Category: SOLAR SYSTEM
ID: 8229
Title: Spatially Resolved Spectroscopy of Titan's Atmosphere and
Surface
PI: Caitlin Ann Griffith
PI Institution: Northern Arizona University

Titan's atmosphere is likened to the Earth's atmosphere; it is nitrogen based,
has a surface pressure of 1.5 bar, and has methane which plays the role that
water plays on Earth. Because methane can exist in both gas and liquid phases,
weather and methane clouds are hypothesized to exist on Titan. Yet Titan's
greater column abundance of atmosphere and the cooler conditions may induce
conditions more quiescent than found on Earth. Here we propose to investigate
the clouds in Titan's atmosphere, first discovered this year (Griffith et al.
1998). Our goal is to study weather processes native to the Earth's lower
atmosphere, yet in the exotic context offered by Titan. By scanning the
0.05'' STIS slit across of Titan's 0.8'' disk, we will build a 16x16 image of
Titan. Each 0.05x0.05'' pixel will consist of a spectrum of resolution 500-
1200 (grating G750L). With methane's varying absorption coefficient acting as
a vertical discriminator, we will resolve the opacity structure of the
atmosphere over a range of altitudes from 400 km down to the surface. This
combination of spectroscopy and imaging will allow us to detect clouds in
Titan's atmosphere, determine their coverage, thickness and altitude range. We
will also measure the surface reflectivity of Titan at 0.9 Mum, and map the
distribution of haze in the northern and southern hemispheres at altitudes
where the haze is formed.
================================================================================
Proposal Category: SNAP
Scientific Category: DISTANT GALAXIES
ID: 8230
Title: Snapshot Survey of Dynamically Close Galaxy Pairs from
z=0.1 to z=0.5
PI: David Patton
PI Institution: University of Victoria

We propose to obtain snapshot images of a large, well defined, and
dynamically selected sample of close galaxy pairs at moderate redshift. These
pairs have been selected from the CNOC2 Field Galaxy Redshift Survey
(0.1 combination with a large low-z sample (SSRS2; z<0.1), is being used for a
detailed study of galaxy mergers and interactions over the range z=0--0.5. At
low redshift, we have established that the majority of pairs satisfying our
criteria (projected separation < 20 h^-1 kpc and line-of-sight velocity
difference < 500 km/s) are undergoing interactions. We have developed an
improved approach to pair statistics that allows us to trace the evolution in
the galaxy merger rate with redshift. We intend to use WFPC2 I-band images to
identify morphological signs of interactions in moderate-z pairs, thereby
determining whether these pairs really are analogous to their local
counterparts. In addition, we will investigate how the rate of
interactions/mergers is changing with redshift. Finally, these images will
allow us to identify a pure sample of interacting galaxies, permitting a
detailed analysis of their properties and a direct comparison with field
galaxies. This study will provide a much needed link between detailed studies
of nearby pairs (e.g., the Antennae) and those at high-z, and it will
elucidate the significance of mergers and interactions in the evolution of
galaxies.
================================================================================
Proposal Category: GO
Scientific Category: SOLAR SYSTEM
ID: 8231
Title: Determination of the radius of comet 19P/Borrelly in
support of the NMP DS1 Flyby
PI: Michel C. Festou
PI Institution: Southwest Research Institute

Comet 19P/Borrelly is the ultimate target of the New Mellinium Program (NMP)
Deep Space 1 asteroid-comet flyby mission. The size of this comet's nucleus
is a critical parameter needed for flyby planning activities. However, as we
describe below, P/Borrelly's radius is not well established. We, the NMP DS1
Science Team, request 1 orbit of HST/STIS time in Cycle 8 to refine the
nuclear size estimate. This program cannot wait until Cycle 9 because of
mission planning constraints and the fact that the comet is likely to be
producing a weak but nonetheless enhanced coma by the time of Cycle 9. We
therefore propose to observe comet P/Borrelly late in Cycle 8 when the
activity level of its nucleus is near its minimum, and quite possibly
negligible, and the comet-Earth distance reaches a local minimum. From a
clear separation of the contributions of the coma and the nucleus in the inner
part of STIS images, we will extract the cross section of Borrelly's nucleus.
In addition to its immediate value for NMP DS1 mission planning, when coupled
to existing data sets, the STIS data will then enable us to model the coma
morphology to better infer the effect of the nucleus outgassing on the comet's
motion.
================================================================================
Proposal Category: GO
Scientific Category: GALAXY POPULATIONS AND INTERACTIONS
ID: 8232
Title: The Youngest Super-Star-Cluster
PI: Daniela Calzetti
PI Institution: Space Telescope Science Institute

Local starbursts are the most immediate counterparts to the high-redshift,
actively-star-forming galaxies, and the study of starbursts and their
constituents can shed light on the initial phases of galaxy evolution. We
propose to use STIS UV spetroscopy to derive an accurate age for the youngest
super-star-cluster candidate known to date in a nearby starburst galaxy. The
stellar cluster is located in the dwarf galaxy NGC5253 at a distance of 4 Mpc.
Its HAlpha equivalent width (from WFPC2 imaging) gives an estimated age of ~2
Myr, and more accurate determinations are hampered by the presence of heavy
dust reddening in the region. The cluster is bright enough in the UV to make
the project feasible with STIS and produce an age determination with an
accuracy +/-0.5 Myr. We will exploit the STIS long slit to derive an accurate
age also for the oldest among the bright stellar clusters (~50 Myr, estimated
from WFPC2 colors). We will use the new data to: (1) break the age/dust
degeneracy, derive the intrinsic luminosity of the clusters, and verify
whether they are proto-globular cluster candidates; (2) use the UV
spectroscopy-derived ages to calibrate the color-derived ages of the other
stellar clusters in the starburst; (3) use the spatial distribution of the
calibrated ages to investigate the spatial and temporal evolution (e.g.,
propagation) of the starburst in NGC5253.
================================================================================
Proposal Category: GO
Scientific Category: AGN PHYSICS
ID: 8233
Title: UV IMAGING OF OPTICAL JETS: A NEW WINDOW ON THE PHYSICS
OF JETS
PI: Stefi Baum
PI Institution: Space Telescope Science Institute

Extragalactic radio jets are highly collimated beams of high energy particles
and magnetic fields issuing forth at relativistic speeds from sub-parsec scale
regions, extending hundreds of kpc through interstellar and intergalactic
space. They are unique in their scope, power, and size. The jets affect their
host galaxies and environments, through kinetic energy output and through
deposition of cosmic rays and magnetic fields into interstellar and
intergalactic space. Despite years of study, fundamental jet parameters such
the magnetic field strength, particle density, jet configuration, bulk Lorentz
factor, and the nature of particle acceleration in the flow remain unknown.
Determining these key parameters and how they vary in different sources is key
to formulating a theory of the physics of the creation and propagation of
these jets. The tightest constraints on the physics of jets come not from
radio observations, but from observations in the optical, UV, and x-ray, where
the lifetimes of the synchrotron emitting particles are measured in hundreds
of years and the particles travel distances of hundreds of parsecs. We
propose to use the unique advantage of STIS' UV sensitivity and high spatial
resolution to obtain images at 1400Angstrom\ and 2400Angstrom\ of a sample of
seven optically-emitting radio jets. This dataset will provide qualitatively
new data with which to constrain the physics of extra-galactic jets.
================================================================================
Proposal Category: GO
Scientific Category: GALAXY POPULATIONS AND INTERACTIONS
ID: 8234
Title: Calibrating Star Formation with the Metal-Rich Starburst
Galaxy M83 (NGC5236)
PI: Daniela Calzetti
PI Institution: Space Telescope Science Institute

A large fraction of the active star-formation in the local and intermediate-
redshift Universe happens in relatively metal-rich regions of galaxies. We
propose to study the structure of the prime nearby example of a metal-rich,
actively star-forming environment: the starburst located in the nuclear region
of the spiral galaxy M83. In M83 the PC gives 1 pc resolution so we can chart
the detailed structure of this dusty but UV-bright system. For this purpose we
will obtain broad-band images in the mid-UV, V, and I bands to locate and
characterize stars, star clusters, and obscuring dust clouds, as well as
HAlpha, HBeta, OIII, and SII narrow band images to diagnose conditions in the
ionized ISM. We will combine these datasets to investigate the presence of
sequential/propagating star formation and establish whether the starburst is a
large-scale coherent or a random process. For this purpose we will measure:
(1) the recent star formation history of both stellar clusters and young
diffuse population; (2) the dust distribution; (3) the structures in the
shocked and photo-ionized gas. This program will allow us to quantitatively
place M83 in the broader context of starbursts in terms of the energetics,
evolution, and internal structures of a key class of burst events, while also
exploring its impact on the surrounding galaxy.
================================================================================
Proposal Category: SNAP
Scientific Category: AGN PHYSICS
ID: 8235
Title: Jets, Winds, and Bubbles in Hercules A?
PI: Stefi A. Baum
PI Institution: Space Telescope Science Institute

The astrophysics of the launching, collimation, and propagation of jets is one
of the outstanding problems in the study of powerful radio loud AGN. During
the course of obtaining WFPC2 F702W snapshot images of the complete 3CR radio
catalog, we came upon the remarkable discovery of a unique phenomenon which,
if verified, has the potential to shed new light on the transport of energy in
powerful radio jets. Our observation of the host galaxy to the powerful radio
source 3C348 (Hercules A), revealed the surprising discovery of interlocking,
kpc scale rings or bubbles aligned near the radio axis and slightly offset
from the galaxy nucleus (Baum Etal\ 1996). The morphology of the radio and
optical rings may suggest that at least in this one source, radio ejection is
episodic. These initial observations were of quite low signal to noise. With
STIS in 50CCD clear and F28X50LP observations, in a 25 minute snapshot
observation we will increase our signal-to-noise by almost an order of
magnitude, allowing us to verify the authenticity of these unique features,
and obtain basic color information as well. Given the possible ramifications
of these results for our understanding of jets, and the remarkableness of the
results, we propose to spend a ~ 25 minute snapshot observation verifying the
result before embarking on more costly (in terms of orbits) follow up
observations in Cycle 9.
================================================================================
Proposal Category: GO
Scientific Category: GALAXY STRUCTURE AND DYNAMICS
ID: 8236
Title: Black holes and gas disks in a complete sample of radio-
loud ellipticals - II: Kinematics
PI: Stefi A. Baum
PI Institution: Space Telescope Science Institute

In Cycle 6 we began a WFPC2 broad- and narrow-band imaging study of the nuclei
of a complete sample of the 21 nearest powerful radio galaxies. Here we
propose follow-up STIS spectroscopy of the nuclear emission-line gas. From
these observations we will measure the black hole (BH) masses, determine the
nature, kinematics, and structure of the central gas disks and obtain a
modeled upper limit to their mass accretion rates. With our available radio
observations, we will be in a unique position to exploit the HST data to
advance our understanding of the nature of BHs in radio-loud galaxies, their
relation to the radio activity, and the nature and physics of their jets. We
will establish the BH demography of radio-loud early-type galaxies out to
\asim 100 -/+c, increasing the number of measured BH masses for these systems
by a factor 5, and enabling systematic and statistically reliable comparisons
of BHs in normal and radio-loud early-type galaxies. Only HST offers the high
spatial resolution required for this study. We have already obtained extensive
other imaging data for the complete sample, at radio (VLBA, VLA), near-IR
(IRTF, KPNO), and X-ray (ROSAT HRI) wavelengths, and have developed the
machinery to model the data.
================================================================================
Proposal Category: GO
Scientific Category: INTERSTELLAR AND INTERGALACTIC MATTER
ID: 8237
Title: Detecting Circumstellar ``Hydrogen Wall'' Emission Around
a Nearby, Sun-like Star
PI: Brian Wood
PI Institution: Smithsonian Astrophysical Observatory

Using the long-slit spectroscopy capabilities of STIS, we propose to try to
detect for the first time nebular Lyman-Alpha emission surrounding a Sun-like
star produced by the interaction of its stellar wind with the ISM. Such
``hydrogen walls'' have likely been detected in absorption around the Sun and
several other nearby stars using GHRS Lyman-Alpha spectra. However, most of
these detections are tentative due to the difficulty in separating the H-wall
absorption from the interstellar H I absorption. Furthermore, even if one
accepts the reality of the detected hot H I absorption components, it is
impossible to prove that circumstellar material is in fact responsible. We
propose to circumvent these difficulties by detecting a hydrogen wall in
emission around 40 Eri A, which is one of the stars for which a tentative H-
wall detection already exists. A successful detection of the expected
circumstellar emission would validate the previous Lyman-Alpha aborption line
studies, and the combined spectroscopic and spatial information provided by
long-slit spectroscopy would contribute valuable new information on the
stellar wind of 40 Eri A and how it interacts with the ISM, especially when
compared with models that we will construct of 40 Eri A's ``astrosphere.''
This new information includes a direct measurement of the distance to the
stellar bow shock, information that we do not possess for any other nearby
star, including the Sun.
================================================================================
Proposal Category: GO
Scientific Category: YOUNG STARS AND CIRCUMSTELLAR MATERIAL
ID: 8238
Title: Collimated Jets and Low Velocity Forbidden Emission from
T Tauri Stars
PI: Patrick Hartigan
PI Institution: Rice University

We propose a program of slitless spectroscopy with STIS to image both the low
velocity component (LVC) and high velocity component (HVC) of forbidden line
emission in single and binary low mass stars undergoing disk accretion. Recent
observations suggest that forbidden emission lines trace two distinct outflows
from classical T Tauri stars, both associated with disk accretion, but with
distinctive kinematic signatures and physical properties. The HVC arises in a
stellar jet, with a mass loss rate proportional to the disk accretion rate,
while the LVC has a much lower velocity than the jet and becomes the dominant
source of forbidden line emission in sources with modest disk accretion rates.
The spatial distribution of the LVC will be traced by images of O ILambda5577,
which emits only in the LVC. Several arguments suggest that the LVC arises in
a slow wind that emerges from the disk at radii out to tens of AU. The
proposed observations will provide a decisive test of this hypothesis. Images
of other lines such as N II Lambda6583 that emit only HVC gas will define the
morphology of the jet as it emerges from the star. These images will quantify
how close to the star the jets become collimated. Our targets, which include
one single star and four binaries of separation ranging from 0.03 AU -- 465
AU, will allow us to determine how binarity affects disk winds and jet
collimation.
================================================================================
Proposal Category: GO
Scientific Category: AGN PHYSICS
ID: 8239
Title: Imaging the NLR in a complete sample of z<0.5 radio-quiet
PG quasars
PI: Heino Falcke
PI Institution: Max-Planck-Institut fuer Radioastronomie

Quasar activity is an important and little understood phase in the evolution
of galaxies, where a central engine leaves its visible imprints in the galaxy
through strong ionization and heating of the ISM. But, what is the structure
of these hot emission line regions in quasars? Do quasars have ionization
cones due to obscuring tori, as in Seyferts? Is this emission line region
different in radio-loud and radio-quiet quasars, and possibly affected by
radio jets shaping the ISM, or is there a contribution from star formation?
How is the emission-line region affected by different host galaxies? To answer
these questions one needs the high resolution of HST. Surprisingly, however, a
thorough study of quasar emission-line regions has not yet been made with HST.
Here we propose to use the Linear Ramp Filters (LRF) and now available
dithering techniques to survey a complete sample of the seven brightest radio-
quiet z<0.5 PG quasars and image their narrow line regions (NLRs) with HST. A
similar survey of Seyfert galaxies we have conducted with the LRFs has
revealed spectacular jet- and bowshock-like structures, and ionization cones.
Since the NLR will be affected by the host galaxy type, energy input from the
central engine, the presence or absence of a nuclear torus, different types of
jets, star formation, or tidal interactions, the program will help us to
investigate a number of key elements of AGN physics.
================================================================================
Proposal Category: GO
Scientific Category: GALAXY STRUCTURE AND DYNAMICS
ID: 8240
Title: Masses and Spins of Black Holes in Seyfert Galaxies
PI: Andrew Wilson
PI Institution: Astronomy Department, University of Maryland

About 20 bright Seyfert 1 galaxies are now known to have very broad (up to
100,000 km s^-1) Fe KAlpha emission lines near 6.4 keV. The line profiles can
be well described by a model involving Fe fluorescence in an accretion disk
within 20 gravitational radii of the hole. The line profile is sensitive to
the metric in this region and attempts have been made to derive the spin of
the black hole for the galaxy with the best measured profile (MCG--6--30--15).
This spin measurement is controversial because of the relatively poor quality
of the line profile, but soon to be launched X-ray missions (AXAF, XMM and
ASTRO-E) will provide profiles of sufficient quality for spin determination.
The goal of the present proposal is to measure black hole masses for a small
sample of these galaxies. Knowledge of both mass and spin provides a complete
description of the hole and gives many benefits, including the Eddington
ratio, the influence of the hole on stars, the variability timescale of the
inner disk, the radiative efficiency of accretion, the source of power for
radio jets and the history of accretion by the hole. We propose STIS
spectroscopy of the disk of ionized gas we have recently discovered in MCG--6-
-30--15 to measure, or obtain upper limits to, the mass of its black hole, and
WFPC2 imaging to search for similar such disks in 7 other galaxies.
================================================================================
Proposal Category: SNAP
Scientific Category: INTERSTELLAR AND INTERGALACTIC MATTER
ID: 8241
Title: A SNAPSHOT Survey of Interstellar Absorption Lines
PI: James T. Lauroesch
PI Institution: Northwestern University

We propose to obtain SNAPSHOT high-resolution STIS echelle observations of the
interstellar absorption lines between 1170 and 1372Angstrom\ towards a sample
of stars with known UV fluxes. By taking advantage of the SNAPSHOT observing
mode we will efficiently obtain large numbers of spectra of O and B-type stars
for ISM studies. Our goals are to explore the homogeneity of the ISM on large
scales and to conduct a census of high-velocity clouds. The selected
wavelength range contains numerous interstellar absorption lines which enable
us to measure the physical properties (density, temperature, depletions) in
individual components. By taking advantage of differential Galactic rotation
we can probe clouds as a function of Galactic radius, and differentiate
between various models for interstellar enrichment. High-velocity clouds can
provide significant information on the structure and evolution of interstellar
shocks, the transfer of energy from stars to the ISM, and the destruction of
interstellar dust grains. This dataset will provide information on the space
density and cross-sections of HVCs in the Galactic disk.
================================================================================
Proposal Category: GO
Scientific Category: GALAXY STRUCTURE AND DYNAMICS
ID: 8242
Title: WFPC2 Imaging of Dust Structures and Star Formation in
the Disk-Halo Interface of Spiral Galaxies
PI: Blair D. Savage
PI Institution: University of Wisconsin-Madison

We propose to obtain \bvi\ \wfpc2\ images of five edge-on spirals to study
star formation and dusty interstellar clouds in the disk-halo interface of
these galaxies. Ground-based and HST images of the nearby (9 Mpc) edge-on
spiral NGC 891 show an unexpected web of hundreds of dust structures at
heights 0.4 <=sssim z <=sssim 1.7 kpc (Howk & Savage 1997). With masses >10^5
-10^6 M(sun), the more prominent extraplanar dust complexes may be sites of
star formation at high-\z, and there is evidence for H II\ regions associated
with unresolved continuum sources far above the plane of NGC 891. We have
established that such high-\z\ dust features and H II\ regions are not unique
to NGC 891. We propose to image five edge-on spiral galaxies (D ~ 17 - 70
Mpc) with the \wfpc2. The proposed \bvi\ images will be used to identify
sites of on-going star formation in the thick disks of these galaxies, all of
which show evidence for high-\z\ dust complexes, and with ground-based H
Alpha\ images will be used to study the stellar content of any such regions.
The resolution and point-source sensitivity of the \wfpc2\ are crucial for
studying these star-forming regions. We will also use these images to study
interstellar matter in the thick disks of these galaxies with unprecedented
detail and derive the fundamental properties of high-\z\ dusty clouds--
including sizes, extinctions, column densities, masses, and gravitational
potential energies.
================================================================================
Proposal Category: GO
Scientific Category: STELLAR EJECTA
ID: 8243
Title: SINS: The Supernova INtensive Study - Cycle 8
PI: Robert Kirshner
PI Institution: Harvard College Observatory

Supernovae reveal the last stages of stellar evolution, create the chemical
history of the Universe, energize the interstellar gas, and occupy the center
of attention for the extragalactic distance scale and cosmology. HST can make
unique contributions to understanding supernovae, as the SINS program has
shown. Now HST is better than ever for this work: STIS is ideal for spatially
-resolved observations of SN 1987A, where a rapidly developing encounter
between the fast-moving debris and the stationary inner ring has just begun.
Our approach for Cycle 8 is the intensive study of a few selected objects
beyond SN 1987A: SN 1993J in M81, SN 1998bu, SN 1998S and a Target-of-
Opportunity observation of a bright, new supernova to be discovered during
Cycle 8. We aim to explore the UV emission from supernovae, exploit the
spatial resolution of HST, and press the late-time observations of supernovae
into uncharted territory. The SINS team provides extensive ground-based
support and analytic power to create an effective observing program that uses
HST to help understand the final, most violent stage of stellar evolution.
================================================================================
Proposal Category: GO
Scientific Category: STELLAR EJECTA
ID: 8244
Title: Probing Stellar Ejecta in SN 1006 through UV Absorption
Spectroscopy
PI: P. Frank Winkler
PI Institution: Middlebury College

The remnant of SN 1006 provides a unique opportunity to study ejecta from a
Type Ia supernova through UV absorption spectroscopy. Absorption lines in the
spectrum of the background Schweizer-Middleditch (SM) star have revealed the
presence of cold Fe and Si with velocities up to 7000kms. These lines surely
are due to ejecta, but extrapolation from a single line of sight to the entire
remnant suggests a mass of Fe less than half the ~ 0.5\: Msun \ expected from
a Type Ia supernova. A reliable inventory of the ejecta requires several such
``core samples'' through the remnant, but until now no other suitable
background UV sources had been identified. A recent search has revealed four
new background objects with which we propose to probe additional lines of
sight through SN 1006: two quasars and two A0 stars. These are fortuituously
well distributed about the 30'\ diameter shell---from only 2'\ away from the
center (even closer than the SM star) to <=sssim 1'\ from the shell rim. In
modest exposures with the STIS we can obtain low-resolution spectra in both
the near- and far-UV which will lead to a much fuller picture of the ejecta
distribution and address the following questions: (1) Are the ejecta in
diffuse expanding shells, or fragmented? In stratified layers, or mixed? (2)
Where is the reverse shock which reheats the ejecta located? (3) Can the
``missing'' Fe from the Type Ia supernova be accounted for?
================================================================================
Proposal Category: GO
Scientific Category: BINARY STARS
ID: 8245
Title: BLACK HOLE ACCRETION OUTBURSTS IN SOFT X-RAY TRANSIENTS
PI: Carole Haswell
PI Institution: University of Sussex

UV observations of soft X-ray transients (SXTs) will be made using STIS. This
is part of an extensive multiwavelength target of opportunity campaign to
monitor newly discovered SXTs in outburst and throughout the subsequent
decline. Recent work establishes that a high proportion of SXTs harbor black
holes, so these observations provide an unrivalled opportunity to obtain high
quality data from an accreting black hole. UV data is a keystone of our
multiwavelength campaign because the disk regions of interest radiate
predominantly in the UV. Emission lines will allow us to probe the kinematics
of the inner disk region. We will examine the relative strengths of the
reprocessed X-ray flux emitted in the UV, and the UV flux generated by viscous
heating in the accretion flow. Multiwavelength observations will probe the
physics of the accretion flow throughout the outburst. The observations will
yield detailed quantitative tests of the models for SXT outbursts. The new
STIS/MAMA capability to perform UV spectroscopy with 125 microsecond time
resolution will be exploited. A proven HST/RXTE echo-mapping experiment will
measure the size of the reprocessing regions in the accretion disk, and thus
probe morphology changes as the decline proceeds. It is unknown what rapid UV
variability we may find; recent RXTE discoveries suggest this may prove a rich
source of information on the dynamics close to the event horizon.
================================================================================
Proposal Category: GO
Scientific Category: HOT STARS
ID: 8246
Title: The youngest massive star clusters in the SMC as clues to
star formation in the early Universe
PI: Mohammad Heydari-Malayeri
PI Institution: Observatoire de Paris

High resolution imaging with WFPC2 has recently allowed us to resolve two
very tight clusters of newly born massive stars in the Small Magellanic Cloud
(N81, N88A; STScI Press Release 25-98, 23 July 1998). These are the youngest
massive stars accessible to direct observations at ultraviolet and optical
wavelengths. Situated in an extremely rare category of \h2 regions in the
Magellanic Clouds (only 5\frac to 10\frac across and of very high
excitation), these stars should rank among the hottest ones in these galaxies.
Although color-magnitude diagrams yield valuable information, follow-up STIS
observations of so identified hot star candidates are imperative for obtaining
spectral types and stellar parameters and establishing the H-R diagrams.
Comparison with models will allow us to derive the evolutionary state of the
stars and clarify the nature of the most intriguing ones. In particular, one
of the stars is a Wolf-Rayet candidate, which is an extremely rare kind of
massive star in the metal-poor SMC. If confirmed by the planned spectroscopy,
this finding will be important for stellar evolutionary models. Since the SMC
is the most metal-poor galaxy observable with very high angular resolution,
the proposed observations will provide valuable templates for studying star
formation in the very distant metal-poor galaxies which populate the early
Universe.
================================================================================
Proposal Category: GO
Scientific Category: STELLAR POPULATIONS IN CLUSTERS
ID: 8247
Title: Hidden new-born massive stars in compact \h2 ``blobs''
of the Large Magellanic Cloud
PI: Mohammad Heydari-Malayeri
PI Institution: Observatoire de Paris

High spatial resolution imaging with WFPC2 is necessary to resolve very tight
clusters of massive stars at birth in the Large Magellanic Cloud. These are
the youngest massive stars accessible to direct observations at ultraviolet
and optical wavelengths. Situated in an extremely rare category of \h2
regions in the Magellanic Clouds (only 5'' to 10'' across and of very high
excitation), these stars should rank among the hottest ones in these galaxies.
Using medium-band continuum filters, we will place the resolved components on
color-magnitude diagrams to identify the exciting stars. Continuum-free He,
ii 4686Angstrom\ images will pinpoint the hottest components and the Wolf-
Rayet candidates of the tight clusters. Imaging in HBeta, O, iii, and HAlpha
will allow us to correct for the extinction and for the nebular emission.
Following our recent HST result on the SMC ``blobs'' N81 (STScI Press Release
98-25, July 1998) and N88A, we are confident that the planned observations
will uncover the stellar contents of the LMC objects N160A1, N83B-1, and N11A.
These objects provide exceptional opportunities for studying various key
phenomena related to massive star formation, in particular whether these
massive stars form in isolation or inside co-spatial tight clusters. The
observations will also enable us to study the ``blob'' phenomenon at different
evolutionary stages in the chemically distinct evironments of the SMC and the
LMC.
================================================================================
Proposal Category: GO
Scientific Category: CLUSTERS, LENSING AND COSMOLOGY
ID: 8248
Title: WFPC2 observations of potential JVAS/CLASS gravitational
lenses
PI: Peter Wilkinson
PI Institution: NRAL University of Manchester

The JVAS/CLASS gravitational lens surveys have been the most successful so far
at finding new arcsecond-scale gravitational lenses. A total of 17 confirmed
systems have been discovered. One surprising result is the number of doubly-
imaged lensed systems compared to ``quad'' configurations. The doubles are
under-represented in the current JVAS/CLASS lens sample by a factor 5 based on
conventional models of the lensing galaxies. This may be partly due to an
observational selection bias that favours the discovery of quad lens sytems
over doubles. It is essential to ensure that no doubly-imaged lensed systems
are missed. Previous WFPC2 observations of candidate lens systems have proved
remarkably successful at confirming new lensed systems by the detection of
lensed images and the lensing galaxies. Recent Cycle 7 NICMOS observations of
JVAS/CLASS candidate systems discovered three new lens systems. However,
several ambiguous candidates from the first two phases of the CLASS survey
remain and two very strong new candidates from the recently observed final
phase of CLASS have also been uncovered. Based on the observed lensing rate in
JVAS/CLASS (1:500) we expect that the majority of these candidates will turn
out to be lenses. There is a companion proposal to this one which aims to
examine confirmed cases of gravitational lensing in the JVAS/CLASS surveys in
more detail.
================================================================================
Proposal Category: GO
Scientific Category: CLUSTERS, LENSING AND COSMOLOGY
ID: 8249
Title: A Strong Lensing Survey of the Mass Distribution in X-ray
Luminous Clusters
PI: Jean-Paul Kneib
PI Institution: Observatoire Midi-Pyrenees

We propose to use WFPC2 for a gravitational lensing survey of the central
regions of 16 X-ray luminous clusters from a statistically complete sample.
Our sample is based on cluster detections in the ROSAT All-Sky Survey and is
representative of the population of rich clusters at z~ 0.2. The proposed
WFPC2 survey will, for the first time, provide an unbiased view of strong
lensing (arcs, multiply imaged systems and arclets) by such systems.
Specifically, the strong lensing features and the shear field in the central
regions of these clusters will be used to reconstruct accurately the mass
distribution from galaxy to cluster scales. The resulting mass maps will be
compared with HRI and ASCA observations in order to probe the dynamical state
of, and the prevalence of substructure in, the cluster core. In combination
with other indicators of the clusters' evolutionary state (e.g. the presence
of a stable cooling flow) our study will provide the first coherent picture of
mass accretion onto clusters at an epoch where cluster growth through mergers
is expected to be common. Furthermore, the accurate mass models resulting from
this survey will allow us to probe fundamental properties of the distant
galaxy population, as well as provide new natural lenses for observations at
longer wavelengths. Finally, the proposed observations will allow us to
investigate the morphological mix and evolution of the cluster galaxy
population.
================================================================================
Proposal Category: GO
Scientific Category: GALAXY STRUCTURE AND DYNAMICS
ID: 8250
Title: Proper motions of bulge stars
PI: Konrad Kuijken
PI Institution: Kapteyn Institute

We request second-epoch observations of two fields in the galactic bulge for
proper motion measurements, using WFPC2. These observations will allow
velocities to be measured with an accuracy of 70km/s, sufficient to study the
rotation properties of the bulge and disk in these fields, the vertical
kinematics as a function of stellar type, and the presence of kinematic
substructure such as might be caused by accretion of small satellites or
dissolution of globular clusters. Further, a proper motion selected color-
magnitude diagram will yield the best possible depiction of the Galactic bulge
turnoff point. The first epoch observations were two-band, single-dither
exposures. For the second epoch we will only use one band, but use two half-
pixel dithered positions to improve the position accuracy.
================================================================================
Proposal Category: SNAP
Scientific Category: STELLAR POPULATIONS IN CLUSTERS
ID: 8251
Title: The Second-Parameter Effect in Metal-Rich, Globular
Clusters: A Snapshot Study of NGC 6441
PI: Horace Smith
PI Institution: Michigan State University

While it has long been known that at least one parameter besides the
metallicity, Fe/H, determines the horizontal-branch (HB) morphology of
Galactic globular clusters (GCs), our ignorance as to the nature of this
second parameter (or parameters) has been a major stumbling block in
understanding the formation history and age of the GC system. The newly-
discovered hot HB populations in the metal-rich GCs NGC 6388 and NGC 6441
provide an unique opportunity for unraveling this second-parameter effect.
Sweigart & Catelan (1998) have presented second-parameter models which predict
unusually bright HBs for these GCs. We propose to test these models by
obtaining B,V,I time-series photometry of the RR Lyrae variables in the core
of NGC 6441 in order to determine whether, as predicted, the pulsation periods
are unusually long as implied by a bright HB luminosity. If confirmed, this
would argue against age or mass loss as the second parameter in NGC 6441 and,
more generally, would have implications for the use of RR Lyrae stars as
standard candles for determining GC distances and ages. A possible new class
of bright RR Lyrae-like variables will also be investigated. The interplay
between stellar evolution and cluster dynamics will be studied by comparing
the radial distribution of the RR Lyrae stars to those of blue and red HB
stars. We waive proprietary rights to any data obtained.
================================================================================
Proposal Category: GO
Scientific Category: INTERSTELLAR AND INTERGALACTIC MATTER
ID: 8252
Title: Extinction Curves of Distant Galaxies
PI: Christopher Kochanek
PI Institution: Harvard-Center for Astrophysics

We propose to measure extinction curves in five external galaxies ranging in
redshift from 0.039 to 0.96 using gravitational lenses that show differential
extinction between the images. The program will more than double the number
of galaxies in which extinction curves have been measured and it will provide
the first such measurements far outside the local group, in early-type
galaxies and at significantly different cosmic epochs. STIS spectroscopic
observations will focus on the 2175Angstrom\ feature, combined with WFPC2 and
STIS photometry to check for variability and extend the wavelength coverage.
For the two systems in our sample that are radio quasars, we will be able to
check for the presence of dust which is gray in the IR--UV spectral range.
================================================================================
Proposal Category: GO
Scientific Category: AGN PHYSICS
ID: 8253
Title: Jet Acceleration of Narrow Line Region Gas
PI: Mark Whittle
PI Institution: University of Virginia

-13pt Recent progress in understanding the kinematics of the Narrow Line
Region (NLR) in Seyfert galaxies has identified three distinct components ---
a high velocity nuclear flow, a more widespread gravitational component, and a
jet-accelerated component. In this proposal, we aim to isolate and study the
jet-accelerated component. A ground based long-slit survey shows that the
kinematic signature of jet interactions while detectable, is usually confused
by the presence of the other two components. Higher spatial resolution is
essential if we are to isolate the jet-perturbed gas. We have selected 11
Seyferts with linear (jet-like) radio structure, pre-existing HST emission
line images, and some indication (kinematic and/or morphological) of a jet
perturbed component. Using STIS, we will obtain one (or in some cases, two)
long slit exposures of the OIII Lambda5007, taken along the radio axis and
through the brighter emission features. This will allow us to zero in on the
jet-accelerated gas --- isolating and measuring its strength, location, and
velocity field, all of which can be used to test the nature of the jet-gas
interaction. Our significant sample size also allows a `demographic' study of
the interaction phenomenon. In the big picture, jet interactions are an
important and widespread astrophysical phenomenon. Unlike other contexts, the
pervasive distribution of line emitting gas in Seyfert nuclei provides the
perfect `highlight' with which to study this interaction.
================================================================================
Proposal Category: GO
Scientific Category: HOT STARS
ID: 8254
Title: A Unique Calibration of Asteroseismology: the DBV GD358
PI: D.E. Winget
PI Institution: Univeristy of Texas at Austin

An improved understanding of the white dwarf stars has a great potential in
both physics and astronomy. Determination of the basic physical parameters of
the white dwarf stars will help us realize that potential; asteroseismology is
the key. We can use asteroseismology to constrain the stellar structure and
evolution, including the stellar mass and even the stellar distance if we can
determine the pulsation indices (k,\ell,m) of the non-radial g-mode light
variations observed in compact pulsators. We made tentative identifications
for GD 358 using a method based on the frequency distribution of consecutive
radial overtone g-modes. A comparison of the amplitude of the pulsation
between the optical and the UV proves to be another independent method to
identify the pulsation indices. Our project is to apply both methods to GD358.
We will measure the optical amplitude with ground-based time series
photometry. By observing the DBV star GD 358 with the HST, we have a unique
opportunity to cross-calibrate the two methods -- essential if we are to have
confidence in the conclusions drawn from either method. The future of
asteroseismology of white dwarf stars hinges on these observations. We
attempted this science previously with HST. The observations were successful,
but GD358 had other ideas (See Justify Duplications section). This exciting
data set only adds to the importance of the proposed calibration observation.
================================================================================
Proposal Category: GO
Scientific Category: FIELD STELLAR POPULATIONS
ID: 8255
Title: Stellar Populations in the Closest Large Low Surface
Brightness Galaxy
PI: Patricia Knezek
PI Institution: The Johns Hopkins University

We propose to observe the closest known large low surface brightness (LSB)
galaxy, UGC 2302, in order to resolve for the first time the massive stars and
tip of the red giant branch in such a system. Large LSBs represent an extreme
star formation environment, both locally within their disks, and on a larger
scale, often residing in underdense regions of the universe. Resolving the
underlying stellar component of such a galaxy can provide critical information
on how stars form and evolve in low metallicity, yet gas-rich environments.
The combination of this data with planned near-infrared, abundance and
molecular gas studies, existing optical UBVRI and HAlpha data, and a VLA HI
map, will allow comparison between the abundance and distribution of stars,
star formation, and neutral gas in unprecedented detail for disk LSBs. In
addition, determination of the characteristics of even the brightest stars in
this galaxy will provide a key calibration of the relative contribution of the
brightest main sequence, giant, and supergiant stars to the optical and near-
infrared colors. This calibration can then be applied to determining the
underlying stellar populations of other massive LSB galaxies using broad-band
filters.
================================================================================
Proposal Category: GO
Scientific Category: HOT STARS
ID: 8256
Title: Deep Helium-Mixing and the Ultraviolet Spectra of Hot
Horizontal Branch Stars
PI: Wayne Landsman
PI Institution: Raytheon STX

There is now good evidence that the luminosities and gravities of hot
horizontal branch (HB) stars in globular clusters are not correctly described
by canonical models of core helium-burning stars. Observations of HB stars in
the critical temperature range 4.2<\log T(eff)<4.3 consistently yield
gravities about 0.4 dex lower, and Stroemgren u magnitudes about 0.4 mag
brighter, than canonical predictions. One possible explanation is provided by
Sweigart's (1997) non-canonical models, in which the HB envelope helium
abundance is enhanced due to prior deep mixing along the red giant branch. The
existence of helium mixing would have important implications for long-standing
problems, such as the origin of the HB morphology and the RR Lyrae distance
scale. However, the critical HB T(eff) range is also where diffusion models
predict a large metal overabundance (due to radiative levitation) in the
photospheres of the slowly-rotating HB stars. A large metal overabundance (
Fe/H > 0) could explain the observed Stroemgren u and \logg anomalies, but
would also predict distinctive UV spectra characterized by strong metal
absorption lines. We propose to ascertain the degree to which radiative
levitation affects the observational properties of blue HB stars by obtaining
STIS low-dispersion UV spectra of 9 hot HB stars in NGC 6752. This will permit
us to disentangle the effects of helium mixing and radiative levitation upon
HB properties.
================================================================================
Proposal Category: GO
Scientific Category: CS
ID: 8257
Title: VV Cephei: The Egress from Chromospheric Eclipse
PI: Philip Bennett
PI Institution: University of Colorado

We propose to obtain STIS and FGS1R observations of the long-period (20.3 yrs)
eclipsing binary VV Cephei (M2 Iab + B0) as it continues to emerge from
chromospheric eclipse. We will also obtain comparison spectra of the similar,
but less interacting (and non-eclipsing) binaries KQ Pup and HR 8164. This
project is a continuation of the Cycle 7 medium length program ``The 1997/98
Eclipse of VV Cephei'' (GO-7269), which used the STIS high resolution echelle
modes to probe the chromosphere of the M supergiant primary. This is done by
observing the absorption spectrum of the primary's chromosphere, which appears
superimposed upon the companion's early-type continuum. Repeated monitoring of
the evolution of the chromospheric absorption spectrum during egress from
total eclipse permits the construction of an empirical model of the
chromosphere and wind of the M2 supergiant. VV Cep is unique among eclipsing
binaries in being sufficiently bright for high resolution spectroscopy. The
proposed STIS observations will probe the wind acceleration region; obtaining
empirical information here is of crucial importance in understanding the
nature of energy and momentum deposition in these cool winds. In addition, we
will observe VV Cep with the newly implemented FGS1R in TRANSFER mode in order
to obtain relative orbit information, and accurate stellar masses.
================================================================================
Proposal Category: GO
Scientific Category: SOLAR SYSTEM
ID: 8258
Title: A Search for Kuiper Belt Object Satellites
PI: Michael Brown
PI Institution: Caltech

The large number of collisions thought to have taken place in the primordial
Kuiper belt suggests that many Kuiper belt objects (KBOs) could have suffered
binary-forming collisions similar to that which formed the Pluto -- Charon
binary. Detection of such KBO binaries would allow us to measure KBO masses,
would help us to understand the past collisional environment of the Kuiper
belt, and would give a context to the otherwise unique-seeming formation of
the Pluto -- Charon binary. We propose a STIS CCD search for binarity in three
known KBOs. The three we target include the largest (1996 TO66), the closest
(1996 TP66), and the most eccentric (1996 TL66) known. We have performed deep
searches around each of these KBOs with the Keck telescope and have not
detected distant satellites; any satellites must therefore be closer than
about ~0.5 arcseconds. Collisionally formed satellites analogous to Charon
should be at distances of only ~0.2 arcseconds; their detection will require
the resolving power and sensitivity of HST. We have carefully constructed an
observing program optimized to detect any such very close satellites.
================================================================================
Proposal Category: GO
Scientific Category: AGN PHYSICS
ID: 8259
Title: The Origin of Blue Wings on NLR Line Profiles
PI: Mark Whittle
PI Institution: University of Virginia

Recent progress in understanding the kinematics of the Narrow Line Region
(NLR) in Seyfert galaxies has identified three distinct components --- a high
velocity nuclear flow, a more widespread gravitational component, and a jet-
accelerated component. In this proposal, we aim to isolate and study the high
velocity nuclear flow. The observational signature of this component is the
famous `blue wing' found on the OIIILambda5007 lines of almost all Seyfert
galaxies. Its ubiquity and amplitude suggest high velocity radial flows are
present, together with a source of opacity (dust). Surprisingly, although this
feature was the first to be identified, its origin and nature are still
unknown. The main stumbling block is its compact size and our ignorance of
the location of the dust. In this proposal, we select four nearby Seyferts
with exceptionally strong blue wings. Using WFPC2 we map the near nuclear
distributions of dust and emission lines, while STIS allows us to track in
detail the near nuclear OIII velocity field. Together, these data allow a
number of tests of the nature and direction of the near nuclear flow. This is
the last zone of the NLR to be understood, and yet it plays a crucial role in
carrying that understanding inwards towards the BLR.
================================================================================
Proposal Category: GO
Scientific Category: CLUSTERS, LENSING AND COSMOLOGY
ID: 8260
Title: Searching for the Hydrogen Reionization Edge of the
Universe at 5 PI: Rogier Windhorst
PI Institution: Arizona State University, Dept. of Physics & Astronomy

\n We propose 36 parallel orbits (4--5 fields of 5--8 orbits each) to
constrain the H Lyman-edge in emission that marks the transition from a
neutral to a fully ionized IGM at a predicted \zion~eq5--15. This edge is due
to recombination from the H Lyman series and Lyman continuum, and can be used
to constrain \zion, one of the most important unknown quantities in large
scale structure and cosmology. Baltz Etal (1998) have shown that there is a
rapid change in absorption around \zion, which can leave a sharp edge signal
in the spectrum of recombining Hydrogen with amplitude \JnuLy~eqfew* 10^-23
erg/cm^2/s/Hz/sr on top of an extragalactic background of JnuEBL~eq5*10^-21,
~3--4 dex below the zodiacal background. The model amplitude uncertainty is
\cge 0.5 dex. HST can constrain this signal in the sky background for Lambda
1Mu, but only with the STIS CCD, its 52*2'' long slit and G750L grating ---
covering Lambda~eq 6000--10,300Angstrom\ and z~eq4--7.5. We expect to set
upper limits to various models for \JnuLy, and possibly make a detection of
\JnuEBL, either of which will constrain \zion. This is a difficult project
that must use contemporaneous STIS calibrations at the bright side of each
parallel orbit to reduce systematic errors to an absolute minimum. We must
develop this technique properly to find out how to optimally develop
instruments for NGST, to make this measurement with greater sensitivity and at
higher redshifts (z~eq7.5--15).
================================================================================
Proposal Category: GO
Scientific Category: GALAXY POPULATIONS AND INTERACTIONS
ID: 8261
Title: Nuclear structure & merger--starburst relation in the
ultraluminous IR galaxy NGC 6240: II. Kinematics
PI: Roeland van der Marel
PI Institution: Space Telescope Science Institute

The ultraluminous infra-red galaxy NGC 6240 has tidal tails and a double
nucleus, suggesting an ongoing merger. We are imaging NGC 6240 with WFPC2 in
Cycle 6, to study the nuclear distributions of stars, dust and ionized gas. We
propose to follow up these observations with STIS spectroscopy, to determine
the stellar and gaseous kinematics. We have already obtained ground-based
spectra, and we are running N-body simulations for a proper interpretation.
Our comprehensive study is aimed at addressing several issues. a The velocity
field of the ionized gas reveals a steep velocity gradient at 12'' from the
double nucleus. STIS will establish whether this is due to rotation around a
suggested 10^10.5 M_sun black hole or to tidal forces in the interaction. b
The far-IR luminosity of NGC 6240 is generally attributed to dust-heating by a
starburst, but a ground-based measurement of the central stellar velocity
dispersion indicates too high an M/L for a starburst. STIS absorption line
spectra will determine whether the stellar motions are in fact relaxed, and
can be used to infer M/L. c An improved measurement of the stellar kinematics
will allow placement of NGC 6240 on the fundamental plane, to address whether
it is consistent with being an elliptical galaxy in formation. d STIS
HAlpha+NII spectra will allow us to search for an AGN component which may
contribute to the dust heating in NGC 6240.
================================================================================
Proposal Category: GO
Scientific Category: STELLAR POPULATIONS IN CLUSTERS
ID: 8262
Title: Nuclear kinematics of the dense globular cluster M15
PI: Roeland van der Marel
PI Institution: Space Telescope Science Institute

The high central density of M15 makes it unique for probing the structure and
evolution of globular clusters. Our WFPC2 images reveal a central cusp in the
star count distribution, consistent with either core collapse or the presence
of a central black hole. To study the dynamics of M15 we have determined
velocities of \asim 1600 stars, and we are currently analyzing state-of-the-
art Keck HIRES spectra and CFHT adaptive optics Fabry-Perot observations.
However, neither ground-based observations nor HST proper motion work can
reliably constrain the dynamics in the central 1--2 arcsec, due to crowding. A
kinematic study of this central region requires the high spatial resolution
and multi-object capability of HST/STIS. We propose to map the central arcsec
spectroscopically in the Mg b region, stepping the 0.1''-wide slit across the
center in 23 steps of 0.1''. Detailed simulations show that this will increase
the number of stars in the central r <= 1.4'' with known velocities from 6 to
\asim 41, which will allow us to determine the velocity dispersion profile
accurate to \asim 2kms. This will yield the mass-to-light ratio as function of
radius, and will constrain the presence of a central black hole or nuclear
concentration of dark remnants. This will be the first HST study of line-of-
sight velocities in any globular cluster, and will yield a unique dataset: no
kinematical data exists at comparable density and spatial resolution for any
other cluster.
================================================================================
Proposal Category: SNAP
Scientific Category: DISTANT GALAXIES
ID: 8263
Title: Snapshots of sub-mJy starburst galaxies
PI: Stephen Serjeant
PI Institution: Imperial College London

Some of the most ambitious and widely-cited extragalactic observations in
recent years have been the constraints made on the star formation history of
the Universe. Madau et al (1996) combined ground-based samples with
photometric redshifts and UV dropout galaxies from the HDF to obtain the
evolving UV luminosity density and hence star formation rate (SFR). From this
they inferred a peak and subsequent redshift cutoff in this star formation. If
correct this is a major result. However, H-alpha and sub-mm surveys find
systematically higher star formation rates, calling into question this
behaviour: in essence, by selecting in the UV, Madau et al are highly
sensitive to dust reddening. We have recently made a new determination of the
comoving star formation density at 0 function of starburst galaxies, which is insensitive to extinction, tracing
both the obscured and unobscured SFR, and is largely free of AGN. We inferred
a comoving SFR ~2* higher than even the de-reddened H-alpha estimates. We
propose a WFPC2 snapshot program of zstackrel<_~0.4 galaxies in our samples,
which dominate the comoving SFR at these epochs, to address: (1) Do
mergers/interactions drive the dramatic evolution in comoving SFR in sub-mJy
starbursts? (2) How, if at all, does reddening affect optical surveys of star
forming galaxies? (3) Is the strong evolution in SFR related to quasar
evolution?
================================================================================
Proposal Category: GO
Scientific Category: AGN PHYSICS
ID: 8264
Title: PDS 456: A radio-quiet analogue of 3C 273
PI: Paul O'Brien
PI Institution: University of Leicester

To understand the nature of Active Galactic Nuclei (AGN), it is important to
explore the full range of parameter space occupied by these powerful objects.
For 35 years, the most luminous, nearby AGN known was the radio-loud quasar,
3C 273 --- the first quasar ever discovered. Now, we have a newly discovered
quasar, PDS 456, which our IR/optical/X-ray data suggests may be the most
luminous object in the local Universe. PDS 456 is radio-quiet, and therefore
provides a view of the nucleus relatively unaffected by the relativistic jet,
which either dominates or contaminates the observed emission from 3C 273. We
propose to use one orbit of HST time to obtain a moderate-resolution STIS
spectrum of PDS 456 in order to: (a) better elucidate its spectral energy
distribution, and in particular its big-blue-bump, thereby constraining AGN
accretion disc models; (b) see if the close similarity with 3C 273 in the
optical/IR extends into the UV; (c) search for UV absorption lines possibly
associated with the strong Fe edge seen in the ASCA data, or with a broad
absorption line region; and (d) determine the UV emission-line spectrum,
particularly LyAlpha for comparison with the very broad Balmer and Paschen
lines.
================================================================================
Proposal Category: GO
Scientific Category: AGN PHYSICS
ID: 8265
Title: Reverberation Mapping of a Narrow-Line Seyfert 1 Galaxy
PI: Bradley M. Peterson
PI Institution: Ohio State University

We propose to monitor the UV spectral variability of the narrow-line Seyfert 1
(NLS1) galaxy Akn 564 at 50 epochs in order to measure the size of the broad
emission-line region via re\-verbera\-tion-mapping techniques. This
measurement, and the virial mass estimate that follows from it, will provide a
key test of NLS1 models and help determine the physical mechanism that
underlies the principal component of AGN spectra, the Boroson--Green primary
eigenvector. These observations will be undertaken in parallel with X-ray and
ground-based optical observations that will allow us for the first time to
explore the multiwavelength variability characteristics of this important
subclass of active galactic nuclei. Possible variations in absorption features
in the UV resonance lines will also be studied.
================================================================================
Proposal Category: GO
Scientific Category: QUASAR ABSORPTION LINES
ID: 8266
Title: The Coherence Length of Lyman-Alpha Absorbers at z ~ 1
PI: Chris Impey
PI Institution: University of Arizona

We propose to use STIS spectroscopy to measure the coherence length of Lyman-
Alpha absorbers in the redshift range 0.5 < z < 1.1, using a new pair of
quasars with a separation of 130 arcseconds. Quasars with this brightness (R =
18.1), redshift and separation are very rare. Coincident absorbers along the
line-of-sight to quasar pairs can reveal the geometry of the diffuse but
highly ionized gas that makes up the Lyman-Alpha forest; this gas represents
the majority of the baryons and it traces the underlying dark matter
distribution. The simple physical history of these low density regions of the
universe means that HST quasar spectra can be used to derive the shape and
amplitude of the power spectrum of mass fluctuations. We will use automated
line selection and fitting software to identically measure the HST spectra and
spectra extracted from SPH supercomputer simulations. The goals are to (a)
make an improved measurement of the coherence length of Lyman-Alpha absorbers
at z ~ 1, (b) determine whether or not the coherence length is a function of
line strength or column density, (c) look for evolution as a function of
column density across the range 0.5 < z < 1.1, and (d) make a direct
comparison between the absorber properties and the predictions of
supercomputer simulations on scales of ~ 0.5 h_100^-1 Mpc.
================================================================================
Proposal Category: GO
Scientific Category: CS
ID: 8267
Title: Taking the Measure of Planets in the Globular Cluster 47
Tucanae
PI: Ronald Gilliland
PI Institution: Space Telescope Science Institute

We propose a sensitive search for planetary companions in close orbits around
upper main sequence stars in 47 Tuc via transit signals from WFPC2 time-series
photometry. About fifty such systems will be detected with planetary radii
errors of only 2-4\ two transits. Follow-up radial-velocity spectroscopy from
the VLT and/or Gemini should provide velocity measurements for the best 25\
planetary masses (sin(i)~1 from transits). Densities to ~15-20\ with
approximately Jovian mass and size providing for the first time meaningful,
physical constraints on extra-solar-planet theory. Many other science
applications will follow from these extensive observations, e.g., U, V, I
imaging well down the White Dwarf cooling sequence in the cluster core, bottom
of main sequence definition to M_V ~13.8, M_I ~12.8, and a definitive survey
for eclipsing binaries. We propose this as a major survey program that will
result in a unique and valuable addition to the HST archive. Albeit
``scientifically risky" in that planets are not yet known to exist in globular
clusters, there is little technical risk -- HST is uniquely capable of
providing the requisite, high-dynamic range, time-series photometry.
================================================================================
Proposal Category: GO
Scientific Category: AGN HOSTS AND ENVIRONMENT
ID: 8268
Title: Lensed Quasar Hosts at High Redshift
PI: Chris Impey
PI Institution: University of Arizona

Gravitational lensing offers a novel way to detect quasar host galaxies at z >
1 and to measure their properties. In lenses, the host galaxy is magnified and
stretched, improving the contrast with the quasar point source. We propose
deep I-band WFPC2 imaging of five lensed systems (z=1.29, 1.59, 2.32 2.55 and
4.50) where rings and arcs of lensed hosts have been detected with NICMOS, to
measure accurately the host colors and luminosities. Preliminary results
suggest that the hosts (of radio-quiet quasars) are not very luminous (L <
L_*). Their properties are more consistent with the evolutionary behavior of
galaxies built up through continuous star-formation, rather than fully-fledged
ellipticals. Even though the sample is small, lensing may offer the best
chance to understand the host properties of the bulk of the high redshift
quasar population. As a fringe benefit, resolving the host structure will help
to determine the dark matter distribution of the foreground lens galaxies.
================================================================================
Proposal Category: GO
Scientific Category: DISTANT GALAXIES
ID: 8269
Title: The Morphological Evolution of Field Galaxies at 1 PI: Richard Elston
PI Institution: University of Florida

We propose to use WPC2 to study the morphological evolution of a near-IR
selected sample of field galaxies with redshifts between 1 and 2. This range
of redshifts is of particular interest since it seems that the properties of
field galaxies changes dramatically at 1 < z < 2. Luminous spirals and early
type galaxies appear to slowly evolve from z ~ 1 to the present but a luminous
and rapidly star forming population emerges by z>2. Determining how these two
seemingly disparate populations are related is the goal of this proposal, in
which we will study how the morphology, bulge, and disk properties of normal
luminous field galaxies change from z ~ 2 to z ~ 1. Given the space density
and luminosity of L_* galaxies we must survey a large area to provide a
statistically significant sample of galaxies. Our sample is complete to K <
20 (drawn from imaging down to K~21.4 at 3Sigma to ensure completeness), and
covers roughly 100 arcmin^2, ensuring we have several hundred galaxies more
luminous than L_* with 1 < z < 2. Near--IR selection is very well suited for
the study of galaxy evolution since the near--IR k-corrections are small,
uniform over galaxy types and rather immune to evolution of the stellar
population. Thus, the galaxy type mix will be the same for all redshifts, and
ensures that the galaxy sample is not biased toward finding more actively
evolving populations.
================================================================================
Proposal Category: SNAP
Scientific Category: GALAXY STRUCTURE AND DYNAMICS
ID: 8270
Title: Proper Motion of the Leo II Dwarf Spheroidal
PI: Michael Siegel
PI Institution: University of Virginia, Department of Astronomy

We propose to continue our investigation into the proper motion of distant
satellites of the Milky Way with a series of HST snapshots around faint
galaxies within our Leo II astrometric field. We will determine a proper
motion for Leo II by combining images from 111 Palomar 200" photographic
plates taken by Baade between 1950-1959 with the HST snapshots. Only with the
fine pixel scale of HST can we realistically hope to match the exquisite Baade
images, which were all taken on the very best nights from a decade of Baade's
allotment of about forty 200" nights a year. As part of Siegel's Ph.D. thesis,
our project on Leo II will: (1) Determine the proper motion of Leo II with
respect to the extra-galactic reference frame, allowing a measurement of the
orbital properties of Leo II from 3-D space velocity (1) Develop techniques
(of growing importance with the declining availability of photographic cameras
and plates) for the astrometric combination of WFPC2 data with older plate
material to derive high-precision proper motions. (2) Determine the proper
motion for an object at the greatest Galactocentric distance yet attempted,
which will provide significant leverage in determining the mass of the Galaxy.
(3) Provide a list of proper-motion selected stars for future refinement of
the proper motion and parallax of Leo II with the Space-Interferometry
Mission.
================================================================================
Proposal Category: SNAP
Scientific Category: STELLAR EJECTA
ID: 8271
Title: A SNAPSHOT Survey of LMC Planetary Nebulae: A Study of
Nebular and Late Stellar Evolution
PI: Letizia Stanghellini
PI Institution: Space Telescope Science Institute

We propose a survey of LMC planetary nebulae (PNe) to study the parallel
evolution of the nebulae and their central stars. We will obtain STIS imaging
and medium-resolution slitless spectroscopy which will yield line fluxes and
nebular morphologies in 7 emission lines (H Alpha, H Beta, \Hei\ <~m 6678
Angstrom, N Ii, O I, O Iii, and [S II]), plus magnitudes of the central stars.
We can gather this data very efficiently in a SNAPSHOT survey, and from it we
will gather a harvest of information: the nebular size, morphology, ionization
structure, density, and mass; and the central star temperature and luminosity
(and therefore its evolutionary state and mass). We will test the correlation
of nebular bipolarity with large progenitor star mass, and correlate PN
morphology and central star evolution in a unique sample of PNe that is free
of distance and other biases. We will compare all the observed and derived
nebular and stellar properties to the environmental stellar mass function to
estimate the progenitor mass. The HST Data Archive has been fully explored
to demonstrate the importance of acquiring new data and the feasibility of the
program. This study will be the most comprehensive of its kind, and will be
unique in the insight it will offer into the combined evolution of PNe and
their central stars. Because we expect these data to be of fundamental
importance to PN studies, we wave 9 months of our proprietary period to
expedite follow-up research.
================================================================================
Proposal Category: GO
Scientific Category: FIELD STELLAR POPULATIONS
ID: 8272
Title: The Horizontal Branches of the M31 Dwarf Spheroidal
Companions And V & VI
PI: Taft Armandroff
PI Institution: Kitt Peak National Observatory

The Galaxy's dwarf spheroidal (dSph) companions show a surprising diversity in
the epochs of their major star formation episode(s), extending from ~15 Gyr to
~3 Gyr. To aid in understanding the origin of this diversity, we need similar
results for M31's dSph companions, the nearest set of morphologically similar
galaxies. Observations of old main sequence turnoffs in the M31 dSphs are
impractical, but with WFPC2 we can establish their horizontal branch (HB)
morphologies, which observations of Galactic dSphs have shown to be a reliable
mean age indicator. Cycle 4 observations indicate that the bulk of the star
formation in And I took place ~10 Gyr ago, though the presence of blue HB and
RR Lyr stars testify to a minor older component. Analysis of Cycle 6
observations of And II are nearing completion, and observations of And III are
scheduled for execution in Cycle 7. Here we seek HST time to complete our
study of the M31 dSphs by observing And V & VI, newly discovered M31 dSph
companions. The primary aim is to determine the HB morphology and thus fix the
epoch of the major star formation episode(s) in these galaxies. Other results
that will follow include an estimate of the true (unprojected) distance from
M31 and limits on the fraction of younger stars, since the data will reveal
any main sequence stars younger than 2--3 Gyr.
================================================================================
Proposal Category: GO
Scientific Category: INTERSTELLAR AND INTERGALACTIC MATTER
ID: 8273
Title: The Oxygen Abundance in Translucent Interstellar Clouds
PI: David M. Meyer
PI Institution: Northwestern University

We propose to obtain high-resolution STIS echelle observations of the
interstellar O I Lambda1356 absorption toward a sample of stars behind six
translucent clouds characterized by large H I column densities and high
extinctions (1.10 <=sssim A_V <=sssim 2.82). Previous GHRS measurements of
this weak feature in diffuse clouds (A_V <=sssim 1) have shown no evidence of
density-dependent O depletion from the gas phase and indicate a total (gas +
dust) interstellar O abundance that is about 2/3 of the solar value. Models
of translucent clouds predict enhanced depletions of gaseous O into molecules
and dust by a factor of 2 or so over those of diffuse sightlines depending on
the cloud homogeneity, grain characteristics, and other factors. The primary
goals of our proposed investigation are to: (1) accurately determine if the O
depletion is enhanced in translucent clouds, and (2) assess the gaseous O
abundance spread in terms of extinction variations. With regard to the latter
objective, our targeted sightlines sample a wide variety of UV extinction
properties and values for the ratio of total-to-selective extinction (3 > R >
5). The lack of any enhanced O depletion among these translucent clouds,
especially if the abundance spread is narrow, would signify that the grain
characteristics are irrelevant to this issue for extinctions of A_V <=sssim 3.
================================================================================
Proposal Category: GO
Scientific Category: SOLAR SYSTEM
ID: 8274
Title: A Size Survey of Cometary Nuclei
PI: Philippe LAMY
PI Institution: Laboratoire d'Astronomie Spatiale

Following our recent success in detecting and characterizing eight cometary
nuclei with the HST, we now propose a minimum program to determine the basic
physical properties of a large fraction of the population of short-period
comets. By acquiring statistically significant data, we can study the origin
of this family of comets and test the hypothesis that they are collisional
fragments from the Kuiper Belt Objects, although with much less insight than
would be provided by our major proposal emphThe Origin of Short-Period Comets.
Our technique takes advantage of the high resolution of the PC2 to clearly
distinguish the nuclei from the surrounding comae provided they come within ~2
AU from Earth. Cycle 8 is exceptionally favorable as 13 short-period comets
meet this criterion. We also propose to observe the favorably-placed Centaur,
29P/Schwassmann-Wachmann 1, which may be in transition from the Kuiper Belt to
the short-period family of objects. Observations will be made through several
filters (some combination of U,B,V,R,I depending on the brightness) to obtain
unique color information. If appropriate, corrections will be applied to the
measured sizes to remove the effect of erosion and retrieve the ``original''
size distribution function. The size and color results obtained during our
survey will nearly double the number of cometary nuclei for which this
information is available.
================================================================================
Proposal Category: SNAP
Scientific Category: AGN HOSTS AND ENVIRONMENT
ID: 8275
Title: ULTRAVIOLET SNAPSHOTS OF 3CR RADIO SOURCE COUNTERPARTS AT
LOW Z
PI: William Sparks
PI Institution: Space Telescope Science Institute

Radio galaxies are an important class of extragalactic objects, representing
one of the most energetic astrophysical phenomena, while extraordinarily
useful as probes of their environments and of the early Universe. In earlier
Cycles we carried out extensive HST snapshot imaging of the 3CR sources to
investigate their optical characteristics. Here we propose a major enhancement
to a superb dataset: to obtain UV images of the 3CR sources at z < 0.1. A
crucial motivation is to offer a zero redshift comparison sample for the
extraordinary radio galaxy morhpologies found at high redshift (where UV
emission is imaged). Are we witnessing the effects of evolution or of
wavelength? We aim to determine whether the alignment effect holds at zero
redshift in the UV; we aim to identify regions of star formation along radio
axes, associated with dust-lanes, tidal interactions, or elsewhere; we will
probe old stellar populations by imaging old hot stars in these predominantly
giant ellipticals and measuring radial and isophotal profiles; we will measure
brightnesses and frequency of UV nuclei and measure dust extinction through
the interesting 2200 Angstrom\ region; we will seek spectral turnovers in
known synchrotron jets and hot spots, and may find new ones with increased
contrast against the host galaxies. The resulting database will be an
incredibly valuable resource to the astronomical community immediately and for
years to come.
================================================================================
Proposal Category: GO
Scientific Category: SOLAR SYSTEM
ID: 8276
Title: UV Spectroscopic Investigation of any Bright, Newly
Discovered Comet
PI: Harold Weaver
PI Institution: The Johns Hopkins University

We propose a emphTarget of Opportunity program to investigate any bright comet
(mboxV<=6) that is newly discovered during Cycle 8, including comets of any
dynamical class. Our main scientific objective is to obtain accurate abundance
measurements for all known UV-emitting cometary species (CO from the CO 4PG
bands, \cotwo\ from the CO Cameron bands, \stwo\ from the \stwo\ B-X bands,
\cstwo\ from CS emissions, and \water\ from OH emissions) and to perform a
deep search for any previously undetected species. The long slit capability of
STIS will allow us to characterize the spatial distribution of the coma
species, so that we can identify those derived from an extended source (e.g.
CO), study the decay of short-lived species (e.g. \stwo), and investigate the
importance of e-impact on CO for the excitation of the Cameron bands. The
latter issue can be definitively resolved during high spectral resolution
observations of any comet having mboxV<=5. If an exceptionally bright (V<=2)
comet is discovered, we would then request Director's Discretionary time to
measure the D/H ratio. This program is a continuation of our efforts in
previous cycles to observe as many comets as possible with HST for the purpose
of doing abundance intercomparisons on a statistically meaningful sample of
objects.
================================================================================
Proposal Category: GO
Scientific Category: STELLAR EJECTA
ID: 8277
Title: The Kinematics of Knots along Herbig-Haro Jets at High
Spatial Resolution
PI: Bo Reipurth
PI Institution: University of Colorado, Boulder

Since the beginning of this decade, it has been speculated that the aligned
knots of Herbig-Haro (HH) jets may correspond to ``internal working surfaces''
resulting from a time-dependent ejection velocity. This interpretation has
received substantial support from recent HST images of some HH jets, which
show that at least some knots do have morphologies that resemble internal
working surfaces. However, the principal signatures of a jet with a time-
dependent ejection velocity are kinematic, having a systematic spatial
velocity variability (with spatial variations over distances comparable to the
knot sizes) along the jet beam. Given the fact that the knots have typical
sizes (along the jet axis) of ~ 0.5'' and knot separations of ~ 2'', the
spatially resolved kinematic characteristics within the knots can only be
observed with HST. We propose to obtain STIS spectra of the two better
studied HH jets : HH 34 and HH 111. HST images have shown that some of the
knots along these jets show the bow shock morphology expected from internal
working surface models. The proposed spectroscopic observations will provide
the kinematical information necessary for a clear confirmation of the
identification of the knots along the HH 34 and HH 111 jets as internal
working surfaces.
================================================================================
Proposal Category: GO
Scientific Category: STELLAR POPULATIONS IN CLUSTERS
ID: 8278
Title: High Precision Photometry of the Core of M13
PI: Charles Bailyn
PI Institution: Yale University

We propose to obtain highly precise main sequence photometry in V and I in the
core of the globular cluster M13. The data will be used to search for a
binary sequence, and to obtain highly accurate main sequence ridge lines and a
deep luminosity function in the core regions of the cluster. The dynamics and
horizontal branch morphology of M13 are anomalous, and it seems likely than an
understanding of the core binary population will be required to resolve the
problems they raise.
================================================================================
Proposal Category: GO
Scientific Category: STELLAR EJECTA
ID: 8279
Title: Cataclysmic Variable Disk Winds: a high time- and
spectral resolution study of flow inhomogeneity
PI: Janet Drew
PI Institution: Imperial College of Science, Technology & Medicine

Disks and disk winds are found in many astrophysical settings. While much
effort has been invested in models for centrifugal MHD disk winds over the
past decade or so, only within the past year has the modelling of radiation-
driven disk winds developed to the point of generating predictions. This
proposed programme of time-resolved UV STIS/E140M observations of the high-
state non-magnetic cataclysmic variables (hNCV), IX Vel, V3885 Sgr, and QU
Car, will explore a striking prediction of the line-driven wind simulations by
Proga et al (1998). These have shown that unsteady, clumped outflow is to be
expected where most of the driving luminosity is produced by the disk rather
than the central star -- a circumstance believed to apply in hNCV. This
programme will identify such clumping as narrow absorption features, first
appearing at low outflow velocities, superposed on UV wind-formed spectral
line profiles. In addition, these winds, if line-driven, are likely at higher
projected outflow velocities to prompt further moving narrow absorption
components analogous to those well-known in OB stellar spectra. Flow times
are so short (~ 50 sec) in these compact binaries that time-tagged HST/STIS
observation is the only option. Observing 3 targets at 3 epochs will both
confront theory directly and yield insights into the systematic trends needed
to build our understanding of line-driven disk winds.
================================================================================
Proposal Category: GO
Scientific Category: CS
ID: 8280
Title: Origins, Structure and Evolution of Magnetic Activity in
the Cool Half of the H--R Diagram: A STIS Survey
PI: Thomas Ayres
PI Institution: University of Colorado

We propose to carry out a major ultraviolet spectral survey of ``coronal''
late-type stars using the powerful capabilities of STIS. The origin of the hot
emissions of otherwise cool stars is a fundamental puzzle in astrophysics, and
is linked closely with another long-standing mystery, that of late-type winds.
Stars are the powerhouses and chemical factories of galaxies. The source of
their ionizing radiations and the driving of their mass loss are of paramount
importance in studies ranging from population synthesis, galactic chemical
evolution, cosmic rays, evolution of planets, to terrestrial ``space
weather.'' Magnetic phenomena---at the heart of coronal activity and perhaps
wind driving as well---are crucial in many cosmic settings, particularly in
dynamic environments such as associated with accretion and mass-transfer.
Stars are accessible ``laboratories without walls'' in which to study the
interplay of magnetic and plasma processes, and seek a unification with the
highly refined---but singular---portrait of the Sun painted by an array of
recent orbiting observatories. The missing link: high-quality ultraviolet
spectra of a diverse collection of late-type stars. Such a major project was
unthinkable before STIS, but the high resolution, broad spectral coverage, and
sensitivity of the second generation spectrograph can capture the stellar
equivalent of a Hubble Deep Field.
================================================================================
Proposal Category: GO
Scientific Category: STELLAR EJECTA
ID: 8281
Title: The Spatial and Ionization Structure of Cas A's Metal-
Rich Ejecta
PI: Robert Fesen
PI Institution: Dartmouth College

Cassiopeia A (Cas A) is the prototype for the class of young, oxygen-rich SNRs
containing material moving at several thousand km s^-1 and exhibiting extreme
O and Si-group (Si, S, Ar, and Ca) abundances due to nuclear processing in a
massive star. Several basic properties of the remnant are not well understood
including shock dynamics of the ejecta, UV and optical line emission
mechanisms, and the puzzling organization of its optical knots into large ring
-like structures. Here we propose the first high-resolution mapping of this
important remnant using WFPC2. Our goal is to survey the small-scale spatial
and ionization structures in these metal-rich ejecta, then use these results
to test reverse shock and CSM-interaction hydrodynamic and line emission
models. We have selected filters which will permit imaging of the remnant's
full +/-6000 km s^-1 expansion velocity in both high and low ionization
emission lines of sulfur and oxygen. These data will provide spatial
information at scales down to 0.001 pc and distinguish oxygen from sulfur rich
emission knots and filaments. Because Cas A's ejecta knots have large proper
motions of 0.2''-0.5'' yr^-1 and exhibit significant structural changes on
timescales of just a few years, we would like to re-image the remnant during
Cycle 10 in order to detect and measure spatial and ionization changes.
================================================================================
Proposal Category: SNAP
Scientific Category: BINARY STARS
ID: 8282
Title: High resolution UV imaging of the binary nucleus of Abell
35
PI: Janet E. Drew
PI Institution: Imperial College

We propose to obtain two high resolution UV images of the extra-ordinary
binary central star of the Planetary Nebula Abell 35 using WFPC2. This system
consists of a rapidly rotating G8III-IV star which dominates the optical
light, and a PG1159-type white dwarf that dominates the UV flux. It is a
challenging test of binary star evolution theories because the interaction
between the binary components is apparent in the high rotation of the
companion. However, the orbital parameters of the system remain poorly
constrained. Our aim is to obtain high resolution UV images of the system
with a view to spatially resolving the binary. We already have data
indicating a projected separation in the range 0.08-0.14^ without achieving
a clear separation of the two stars. The requested observations will improve
on this to give direct and more precise measurements of the orbital separation
and position angle. These snapshot images will provide first epoch data for
the definition of the binary orbit of the central star of Abell 35.
================================================================================
Proposal Category: GO
Scientific Category: AGN PHYSICS
ID: 8283
Title: High Abundances in Luminous Quasars: A Test Case
PI: Jack Baldwin
PI Institution: Cerro Tololo Interamerican Observatory

Recent studies of high-redshift quasars suggest that their broad emission line
regions (BELRs) have metallicities (Z) that are generally above solar. A
natural conclusion is that quasars are associated with an epoch of very rapid
and extensive star formation during the birth of massive galaxies. However,
these metallicity estimates rest on just a few emission lines, most notably N
V Lambda1240. We have embarked on a study of other BEL metallicity
indicators, especially other nitrogen lines. The N IV Lambda1486 and N III
Lambda1750 intercombination lines can be useful abundance probes, but are
usually too weak to measure. The only other permitted N line, N III Lambda990,
should be an excellent diagnostic but its short wavelength make observations
difficult. The quasar Q0353--383 is an ideal test case for all these abundance
indicators because the intercombination lines are known to be strong (Osmer
1980). We propose HST-STIS observations to measure N III 990 and other
emission lines below LyAlpha to complement our ground-based spectra. The
combined data set will complete our reconnaissance of the nitrogen spectrum,
measure the gas density and constrain the ionization using abundance-
independent line ratios. We will compare results from the various abundance
diagnostics, and derive a definitive nitrogen abundance from several stages of
ionization.
================================================================================
Proposal Category: GO
Scientific Category: AGN PHYSICS
ID: 8284
Title: Deep STIS Observations of BALQSO PG 0946+301
PI: Nahum Arav
PI Institution: Institute of Geophysics and Planetary Physics

A major goal in the study of AGN outflows is the determination of the
ionization equilibrium and abundances (IEA) in broad absorption line (BAL)
QSOs. In the last few years it has become clear that partial coverage of the
continuum source and saturation are common in BALs, and these frustrate
attempts to determine the IEA from available HST data because of limitations
imposed by the S/N ratio and spectral coverage. We therefore propose to
reobserve the most suitable BAL IEA target: PG 0946+301. These observations
will allow us to measure saturation using at least six different diagnostics,
and therefore derive real column densities. The wide UV spectral coverage
will enable us to measure several occurrences of BALs from different ions of
the same element which are the key to determining the IEA of the flow. In
addition, the combined STIS/FOS data will yield the first possibility of
detecting BAL variability in the rest-frame far UV, and the data on the
highest ionization BALs will shed light on the connection between the BAL and
warm absorber phenomena. This proposal is a crucial part of a
multiwavelength campaign on PG 0946+301 which also includes ASCA, FUSE and
ground-based observations. Taken together, we believe these data will
revolutionize our understanding of quasar outflows.
================================================================================
Proposal Category: GO
Scientific Category: STELLAR EJECTA
ID: 8285
Title: Using STIS to Unravel Planetary Nebulae
PI: William B. Latter
PI Institution: SIRTF Science Center/Infrared Processing and Analysis
Center/Caltech

We propose new STIS observations to study the UV/optical properties of a
sample of young planetary nebulae. Objects in this class display remarkable
complexity that has prevented a full understanding of post-asymptotic giant
branch stellar evolution. With NICMOS we have imaged several such objects in
H_2 and other filters. H_2 emission can probe shocks (winds/jets) and the
photodissociation region through near-IR emission. To unravel the complex
structure (spatial and kinematic) and distinguish between excitation
mechanisms (UV or shock), we must follow up our NICMOS observations with STIS.
We will use STIS in various long slit modes (low and medium resolution and
echelle) to achieve the following objectives: (i) Spatially separate shock
structures from radiatively excited regions by looking at diagnostic lines
such as ionS2, (ii) obtain kinematic information in the vicinity of the
ionized gas--PDR interface and (iii) interpret the spatially resolved results
from (i) and (ii) in light of the ``interacting stellar winds'' theories, in
which the PN morphology is created as the fast PN wind plows into the slower,
denser AGB wind. We require observations with HST to get the highest possible
spatial resolution and stability for line ratio studies throughout the complex
nebulae. Several emission lines have been selected to be observed at high
spectral resolution for measurement of wind velocities and structure.
================================================================================
Proposal Category: GO
Scientific Category: GALAXY STRUCTURE AND DYNAMICS
ID: 8286
Title: Absolute Proper Motions of Nearby Dwarf Spheroidal
Galaxies
PI: Edward Olszewski
PI Institution: Steward Observatory, U. of Arizona

We propose to measure precise absolute proper motions for four dwarf
spheroidal satellites of the Milky Way using spectroscopically-confirmed
background QSOs to define a zero-velocity reference frame. Three epochs
within the 2 years separating 3 HST cycles will yield systemic tangential
velocities of UMi, Car, Scl, (and For) to +/- 78 kms\ (+/- 130 kms). These
are worst-case velocity precisions and they are likely to be 2* smaller. With
2-3 QSOs per galaxy and 3 observations per QSO field we will have a clear
understanding of the systematic errors that could affect the astrometry. We
will test whether the halo contains a small number of massive streams
containing several dwarf galaxies, or whether the individual halo dwarfs are
traveling along independent orbits. HST is essential to achieving the high
precisions needed to conclusively compare the projected orbital motions of the
individual galaxies; even with our conservative uncertainties, we are
competitive with the best ground-based efforts with only a 2 year baseline.
We will also use our results to improve our estimate of the mass of the Galaxy
interior to ~ 100 kpc.
================================================================================
Proposal Category: GO
Scientific Category: QUASAR ABSORPTION LINES
ID: 8287
Title: A Search for transparent lines of sight with
Intergalactic HeII absorption towards 26 bright z > 2.9
Quasars
PI: Dieter Reimers
PI Institution: Hamburger Sternwarte

We propose to probe the far-UV continuum fluxes of 26 new bright (B~ < 17,5)
2.9 <= z <= 3.2 QSOs from the Hamburg Bright Quasar Survey by means of single-
orbit STIS exposure, with the aim of identifying more suitable bright objects
for detailed studies of intergalactic HeII absorption over this redshift
range. According to improved estimates of the Ly C opacity of the IGM, we
expect at least 3 positive detections. Together with 15 FUSE Cycle 1 targets
with z < 2.9, successful detections will provide detailed information on the
HeII reionization history of the universe which appears to occur close to z =
2.9 and on the diffuse intergalactic medium.
================================================================================
Proposal Category: GO
Scientific Category: QUASAR ABSORPTION LINES
ID: 8288
Title: UV brightest known intermediate redshift QSO:, A
\boldmath z \unboldmath = 1.15 DLA and metals in the Ly
\boldmath Alpha \unboldmath forest
PI: Dieter Reimers
PI Institution: Hamburger Sternwarte

We propose to observe with STIS the DLA system at z = 1.15 and the Ly Alpha
forest in HE 0515-4414, with V = 14.9 and z = 1.71 the brightest known QSO
above z = 1.5 (also in the UV with a flux of > 5 \cdot 10^-15 erg cm^-2 s^-
1Angstrom ^-1). We plan to observe the unabsorbed range from 2300 to 3100
Angstrom\ at a resolution of ~ 30 000 with the following aims: (i) to detect
the Ly Alpha forest at z < 1.5 in order to investigate the evolution of
metallicity in the Ly Alpha forest by means of optical spectra at extremely
high resolution and S/N covering C\IV (z = 1 to 1.5) and Si\IV (1.3 to 1.5);
(ii) to determine element abundances in the damped Ly Alpha system at z = 1.15
from ions not accessible from the ground ( H\I, S\II, S\III, P\II, P\V,
Si\III, Si\IV, C\II, C \III, O\I, N\II, N\I, Ar\I, etc.).
================================================================================
Proposal Category: GO
Scientific Category: YOUNG STARS AND CIRCUMSTELLAR MATERIAL
ID: 8289
Title: Development and evolution of YSO outflows and jets
PI: Christopher Burrows
PI Institution: Space Telescope Science Institute

XZ Tauri, HL Tauri, and HH 30 are three young stars which can be observed
simultaneously in a single WFPC2 pointing. Broad-band HST imaging has
revealed that the XZ Tauri binary is the source of an elongated bubble of
emission nebulosity nearly 5'' long. In new images of these objects obtained
in March 1998, we discovered that the XZ Tau bubble had expanded significantly
and had become markedly limb-brightened since 1995. This behavior suggests
that we are witnessing, for the first time, the earliest stages of development
of a Herbig-Haro bowshock, perhaps the initial formation of its post-shock
cooling zone. We propose to test this hypothesis with emission line imaging
and temporal monitoring of the bubble's size and brightness. Simultaneously
with the XZ Tau study, we will observe the jets and reflection nebulosities of
HH 30 and HL Tauri. Monitoring of HH 30 is particularly important, as our
1998 imaging also revealed that a very large reflected light asymmetry has
developed in this prototype young stellar object accretion disk system.
================================================================================
Proposal Category: GO
Scientific Category: CS
ID: 8290
Title: Weather, moons, and orbit of the brown dwarf Gl 229B
PI: Christopher Burrows
PI Institution: Space Telescope Science Institute

Gl 229B is the only unambiguous brown dwarf. It can be imaged with high
astrometric and photometric accuracy only by HST. For the first time, we have
an opportunity to study the object over an extended period of time. The
possibilities for detecting planets or moons orbiting Gl 229B are quite
promising because Gl 229B's small size, mass, and distance from us amplify the
expected signals. We will be able to detect a companion if it is almost as
small as Earth, and in a close orbit (similar to those occupied by Jupiter's
moons) that is favourably inclined. Such a body in such an orbit might well
have formed in the accretion disk from which Gl 229B grew. On the other hand,
a higher mass companion in a wider orbit will be detected by the reflex motion
it induces on Gl 229B itself, with a search radius limited only by the time
baseline over which the observations are carried out. Any detection of a
companion will allow the immediate determination of the mass of Gl 229B. An
additional benefit of the monitoring proposed here is that if there are
stationary and long lived surface features on Gl 229B like Jupiter's giant red
spot, we will detect them and hence measure the rotation period of the brown
dwarf. Finally, variations in the intrinsic luminosity could be caused by
weather in its highly convective atmosphere. Even if no planetary companion
is detected, this proposal will establish the variability or lack thereof of
this unique object.
================================================================================
Proposal Category: GO
Scientific Category: FIELD STELLAR POPULATIONS
ID: 8291
Title: The Alpha-Element/Iron Ratio in Starburst Populations
PI: Claus Leitherer
PI Institution: Space Telescope Science Institute

We propose STIS observations of A and F supergiants in NGC1569, the closest
starburst galaxy. Spectra around 6200 Angstrom\ taken with the G750M grating
will be used to determine element abundances of Fe and several Alpha-elements.
The galaxy has experienced a strong starburst over the past few hundred Myr
and possibly only very few and much less intense episodes of star formation at
earlier epochs. Chemical evolution models predict a significant Alpha/Fe
enhancement in the galaxy. This prediction is difficult --- if not impossible
--- to verify from an abundance analysis of the gas phase. However, the issue
can be settled with a direct abundance measurement in recently formed stars.
The proposed STIS observations, in combination with the stellar atmosphere
tools we have developed will allow such an abundance determination. These
observations are the first abundance measurements of individual stars outside
the Local Group. The determination of the Alpha/Fe ratio is fundamental to our
understanding of the chemical evolution history of this galaxy. It will also
constrain the treatment of mixing processes in the hot and cold phase of the
ISM and the enrichment of the intracluster and intergalactic medium.
Ultimately, understanding local starbursts in detail will allow us to
extrapolate to high redshift and to better understand galaxy evolution in the
early universe.
================================================================================
Proposal Category: GO
Scientific Category: CS
ID: 8292
Title: Calibrating the Mass-Luminosity Relation at the End of
the Main Sequence
PI: Todd Henry
PI Institution: Harvard-Smithsonian Center for Astrophysics

This is a continuation request for GO 6047/6566/7493. 5pt We propose to use
HST-FGS1R to calibrate the mass-luminosity relation (MLR) for stars less
massive than 0.2 Msun, with special emphasis on objects near the stellar/brown
dwarf border. Our goals are to determine M_V values to 0.10 magnitude, masses
to 5\ than double the number of objects with masses determined to be less than
0.20 Msun. This program uses the combination of HST-FGS3/FGS1R at optical
wavelengths and ground-based infrared speckle work to examine nearby,
subarcsecond binary systems. The high precision measurements with HST-
FGS3/FGS1R (to 1 mas in the separations) for these faint targets (V = 10--15)
simply cannot be equalled by any ground based technique. As a result of these
measurements, we are deriving high quality luminosities and masses for the
components in the observed systems, and characterizing their spectral energy
distributions from 0.5 to 2.2 Mum. Several of the objects included have M <
0.1 Msun, placing them at the very end of the stellar main sequence, and in
fact making them brown dwarf candidates. The payoff of this proposal is high
because all 8 of the systems selected have already been resolved with HST-
FGS3 during Cycles 5/6/7, and contain most of the reddest objects for which
masses can be determined.
================================================================================
Proposal Category: GO
Scientific Category: GALAXY POPULATIONS AND INTERACTIONS
ID: 8293
Title: Spatial Structure of Super Star Clusters in NGC 1569
PI: Dan Maoz
PI Institution: Tel-Aviv University

HST and ground-based observations have revealed that a large fraction of star
formation in starburst environments occurs in compact super star clusters
(SSCs). SSCs appear to be gravitationally bound, implying a very high star-
forming efficiency, which may be difficult to explain. We propose spatially-
resolved long-slit spectroscopy of three of the nearest and brightest SSCs in
NGC 1569. A fortuitous alignment allows positioning the three SSCs (A1, A2,
and B) simultaneously in the slit. The HST + STIS resolution and sensitivity
will allow resolving the clusters (half-light radius = 1.6 pc) into three
radial bins at 1-4 pc. With our 3000--10,000 Angstrom spectra, we will
determine the dominant stellar populations at each radius, and hence the
structural star-forming history of the clusters. The only SSC that has been
studied in this way is R136 in the LMC, and it shows evidence for population
segregation, suggesting the massive stars form last, in the already-
established potential well of lower-mass stars. We will test this idea in
three additional, more massive, SSCs. The measured radial stellar-population
gradient, combined with Keck high-spectral-resolution data will refine the
total mass estimate for the cluster and constrain the initial mass function.
The mass estimate can reveal the presence or absence of low-mass stars, and
thus address the open question of whether SSCs ultimately evolve into globular
clusters.
================================================================================
Proposal Category: GO
Scientific Category: CS
ID: 8294
Title: Is SiO observed in the uv spectrum of Beta Gem?
PI: Carole Jordan
PI Institution: University of Oxford

Beta Gem (HD 62509) is a K0 III star with relatively low ultraviolet (uv)
emission line fluxes and X-ray emission, and is thought to be a helium core-
burning `clump' giant. However, since it lies at a distance of only about 10
parsecs the fluxes at the Earth are sufficient for detailed spectral studies
in the uv. Although our main interest in the star has been in modelling for
the purposes of establishing and understanding the energy balance
requirements, this proposal is concerned with a specific aspect of its
spectrum around 2320 Angstrom to 2365 Angstrom. In Beta Gem (HD 62509) and
cooler giants the strongest lines in this region are those of C II, Si II and
Fe II. The spectrum of Beta Gem (HD 62509) is so far unique in that it also
shows a number of narrow emission features that are not observed in the cooler
stars, with an overall structure that suggests the presence of a molecular
band. We wish to investigate the possibility that this is the A ^1PI - X
^1Sigma (0 - 0) band of SiO, which has never been identified in an
astrophysical spectrum. This requires the high spectral resolution of STIS.
Other bands in the above system would then also be expected in the region from
about 2300 Angstrom to 2500 Angstrom. Chromospheric models would be used to
understand the presence of the SiO band system in Beta Gem (HD 62509) and its
absence in cooler giants.
================================================================================
Proposal Category: SNAP
Scientific Category: BINARY STARS
ID: 8295
Title: Anomalously Blue Giants: Possible Precursurs to Subdwarf
B Stars
PI: Brian Chaboyer
PI Institution: Dartmouth College

Subdwarf B (sdB) stars are evolved hot stars (24000 to 35000K) that are
commonly found in the field of our Galaxy and have recently been identified in
old disk, metal-rich clusters. They are likely to be one of the most
important contributors to the upturn in the far-ultraviolet (FUV) flux
exhibited by many elliptical galaxies and the bulge of M31. It is believed
that sdB stars are core helium burning stars with very thin hydrogen
envelopes. The mechanism which stripped the hydrogen envelope is not
currently known. We propose that sdB stars are formed due to binary
interactions. In particular, they have evolved from anomalously blue giants,
which in turn have evolved from blue stragglers. These `blue' giants have
been recently identified by us in NGC 188 and 6791, and are 0.1 -- 0.2 mag
bluer in B-V than the normal red giant stars in each cluster. If our theory
is correct, a significant fraction of these giants will have white dwarf
companions that could be detected in the FUV. We propose to test this
scenario in a snapshot program to obtain STIS FUV images of a dozen of the
bluer giants in both clusters. The giants themselves emit a negligible amount
of FUV flux and would be undetectable without a hot companion. Confirmation
of the presence of hot companions would lend strong support to the theory that
the anomalous giants are the binary precursors to the sdB stars.
================================================================================
Proposal Category: GO
Scientific Category: STELLAR POPULATIONS IN CLUSTERS
ID: 8296
Title: Massive blue clusters in M31
PI: Paul Hodge
PI Institution: University of Washington

We propose to study six massive blue clusters in M31. U, B, V photometry will
provide important data on the stellar population of these clusters, a type
virtually unknown in the Milky Way. Comparison of the cluster CMDs with models
will allow us to age-date them and to explore the evolutionary parameters,
such as stellar mass loss, that are more difficult to study in our Galaxy's
much more sparsely-poulated young clusters, which have very few evolved stars
in any given cluster. Photometry of the supergiant stars will allow us to
constrain the metallicity, one of the probable parameters relevant to the
formation of this type of massive cluster.
================================================================================
Proposal Category: GO
Scientific Category: INTERSTELLAR AND INTERGALACTIC MATTER
ID: 8297
Title: The Physical State of the Starburst Outflow in NGC1705
PI: Claus Leitherer
PI Institution: Space Telescope Science Institute

We propose STIS echelle M mode spectroscopy from 1200 Angstrom\ to 3000
Angstrom\ of the nearby starburst galaxy NGC1705. Our selected sightline
towards the super star cluster NGC1705-1 probes the physical conditions in the
starburst-driven galactic superwind. The resolution of ~10 kms\ is a factor-of
-30 improvement over existing HST data and allows a study of the complex
outflow kinematics. Multiple supershells are expected to be resolved. Together
with FUSE data, the proposed observations will constrain the energetics of the
cold and hot gas and help determine if the outflow material can escape from
the galaxy. Several weak lines will be measured at sufficiently high S/N to
derive column densities and abundances. Previous suggestions of an Alpha-
element/Fe enhancement will be verified or rejected using weak Si II, S II, Cr
II and Zn II lines. Dust depletion in the outflow will be studied with Fe II
lines. No other starburst-driven outflow can be observed with STIS at even
remotely similar resolution and S/N. The chosen sightline will allow us to
generalize our results to the overall properties of the galaxy outflow, to
search for implications for similar galaxies at cosmological distances, and to
add to our understanding of QSO absorption lines. We will reduce the
proprietary period to six months to allow the community rapid access to these
template spectra.
================================================================================
Proposal Category: GO
Scientific Category: BINARY STARS
ID: 8298
Title: Binary Interaction in the Mira AB Accreting System
PI: Margarita Karovska
PI Institution: Smithsonian Astrophysical Observatory

The Mira AB system belongs to a class of detached binaries in which a compact
object accretes mass from the wind of a cool giant or supergiant. This system
provides a unique laboratory for detailed study of wind accretion processes
because it is the only wind-accreting binary that has been resolved with the
HST and whose components can be studied individually. In 1995, we resolved
this binary using the HST FOC camera images and objective prism observations.
We detected significant asymmetries in the giant's atmosphere and found
evidence for possible interaction with its companion. A study of the
asymmetric outflow from Mira can be pivotal for understanding the early
formation of asymmetries in the atmospheres and the circumstellar envelopes of
planetary nebulae progenitors, because Mira-type stars are a critical link in
the evolutionary path toward planetary nebulae. We propose to carry out
follow up HST observations using STIS to obtain high spatial/spectral
resolution observations of each component of the system. Our main scientific
objectives are: 1. To further study the signatures of the interaction between
Mira A and Mira B; 2. To determine if the asymmetries in Mira A are related to
a bipolar outflow or structures in the extended atmosphere; 3. To carry out
detailed study and modeling of the accretion processes in the system.
================================================================================
Proposal Category: GO
Scientific Category: AGN HOSTS AND ENVIRONMENT
ID: 8299
Title: Mapping the Dynamics of the quasar 3C 48
PI: Walter Jaffe
PI Institution: Leiden Observatory

In quasars and radio galaxies there is a relation between the properties of
the radio source and those of the (optical) line-emitting gas. Compact steep-
spectrum (CSS) radio sources often show disturbed kinematics of the
interstellar gas coupled to associated radio components, providing evidence
for gas outflow. The interaction between radio jets and the host galaxy ISM
may be responsible for the jet confinement to small scales and can contribute
to the ionization of the medium and lead to star formation. Detailed study of
the circumnuclear region is essential in understanding the processes that
drive the kinematics, physical conditions and morphology of the line emitting
gas. The archetypical, nearby (z=0.37) quasar 3C 48 is an unusual CSS radio
source with excess far-IR emission, whose one-sided radio jet is aligned with
the extended ionized emission and a putative second nucleus. The radio
morphology and our ground based integral field spectroscopy of 3C 48 suggest
the jet is interacting with its immediate environment. 3C 48, because of its
high AGN luminosity and proximity, is a good candidate to search for kinematic
signatures of the radio jet-gas coupling and/or of a recent interaction. We
propose STIS long slit spectroscopy in several slit positions to map the
kinematics and physical conditions of the extended emission line gas and their
relations to near-nuclear star forming regions found in existing HST images.
================================================================================
Proposal Category: GO
Scientific Category: YOUNG STARS AND CIRCUMSTELLAR MATERIAL
ID: 8300
Title: Testing the Falling Evaporating Bodies hypothesis on the
\hb\ star \hd
PI: Anne-Marie Lagrange
PI Institution: Observatoire de Grenoble

It has been recently proposed that several Herbig stars exhibit \spec\
variable features similar to those of the older, Main Sequence star, \bpw, and
by analogy attributed to evaporation of cometary-like bodies falling on to the
star. The presence of such around Herbig stars is an important issue regarding
the evolutionary timescales of planetary systems formation. However, this
hypothesis is still controversial and needs to be tested. The only way to do
so is to compare the observations with detailed, dedicated simulations, as we
successfully did on \bpw. This is also the only way to reliably estimate the
physical (sizes, evaporation rates, etc) and orbital parameters of the
suspected infalling bodies. We recently adopted this approach in one of the
sofar most convincing cases of \hb\ candidates for cometary infalls, namely
\hd, comparing IUE data with the predictions of our model. First tests could
be done, eventhough limited, due to the limited Signal/Noise provided by IUE
and to the limited number of available data. Important differences have
already been found between this object and \bpw. We propose to record STIS
data to test the cometary hypothesis for this star into more details and more
quantitatively, from both dynamical and chemical points of view.
================================================================================
Proposal Category: SNAP
Scientific Category: GALAXY STRUCTURE AND DYNAMICS
ID: 8301
Title: A SNAPSHOT SURVEY OF X-RAY SELECTED CENTRAL CLUSTER
GALAXIES
PI: Alastair Edge
PI Institution: University of Durham

Central cluster galaxies are the most massive stellar systems known and have
been used as standard candles for many decades. Only recently have central
cluster galaxies been recognised to exhibit a wide variety of small scale
(<100 pc) features that can only be reliably detected with HST resolution. The
most intriguing of these are dust lanes which have been detected in many
central cluster galaxies. Dust is not expected to survive long in the hostile
cluster environment unless shielded by the ISM of a disk galaxy or very dense
clouds of cold gas. WFPC2 snapshot images of a representative subset of the
central cluster galaxies from an X-ray selected cluster sample would provide
important constraints on the formation and evolution of dust in cluster cores
that cannot be obtained from ground-based observations. In addition, these
images will allow the AGN component, the frequency of multiple nuclei, and the
amount of massive-star formation in central cluster galaxies to be assessed.
The proposed HST observations would also provide high-resolution images of
previously unresolved gravitational arcs in the most massive clusters in our
sample resulting in constraints on the shape of the gravitational potential of
these systems. This project will complement our extensive multi-frequency work
on this sample that includes optical spectroscopy and photometry, VLA and X-
ray images for the majority of the 210 targets.
================================================================================
Proposal Category: GO
Scientific Category: INTERSTELLAR AND INTERGALACTIC MATTER
ID: 8302
Title: Lyman alpha emission in starburst galaxies
PI: Daniel Kunth
PI Institution: Institut d'Astrophysique de Paris

We propose to perform a deep study of Ly-alpha\ emission and destruction in 3
star-forming galaxies. These objects have been already observed with the GHRS
and exhibit a variety of situations, with Ly-alpha\ showing P Cyg profiles,
secondary emissions or even a deep damped absorption line with no emission.
They also span a range of intrinsic properties: IZW18 is a gas-rich, metal
deficient dust free dwarf galaxy, Haro 2 has a simple morphology while IRAS
08339+6517 is a luminous IRAS starburst galaxy with more dust and complex Ly-
alpha\ profile. The use of STIS will allow for the first time to study the
geometrical/kinematical configuration of the ionized and neutral gas across
the galaxies nuclear regions and pin point the effects of porosity and the
kinematical structure of the ISM, that may play the key roles (in addition to
dust) in the detectability of the line. This study will have important impact
for cosmology since Ly-alpha\ emitters are nowaday found at high-redshift. We
strongly emphasize that since Ly-alpha\ is primarely a diagnostic of the ISM,
a full understanding of how the ISM and Ly-alpha\ are related is a necessary
step before we can hope to correlate Ly-alpha\ to the cosmic star-formation
rate. Our results will be interpreted against the model of superbubble
evolution developed with G. Tenorio Tagle.
================================================================================
Proposal Category: GO
Scientific Category: GALAXY POPULATIONS AND INTERACTIONS
ID: 8303
Title: What is 52W036?
PI: Steven
PI Institution: Majewski

University of Virginia, Dept. of Astronomy
================================================================================
Proposal Category: GO
Scientific Category: HOT STARS
ID: 8304
Title: Stellar Winds from Central Stars of Young Planetary
Nebulae
PI: Sun Kwok
PI Institution: University of Calgary

Stellar winds from central stars of planetary nebulae (CSPN) are responsible
for driving the dynamical expansion as well as shaping the morphology of
planetary nebulae (PN). The stellar winds also remove material from the thin
hydrogen atmosphere of the central star, determining whether a PN will stay
hydrogen burning throughout its lifetime or will go through an episode of
thermal pulse and revert back to the asymptotic giant branch. Wind signatures
have been seen in the IUE spectra of a number of evolved PN with high
temperature central stars but very little is known about the properties of the
stellar winds in young PN when the nebular morphology is being shaped. We
request HST time to carry out sensitive UV spectroscopic observations of a
number of CSPN. With good S/N spectra, we will be able to fit the line
profiles of resonance lines to deduce the mass loss rates and terminal
velocities of the stellar winds. We propose to observe 4 young PN selected for
their small angular sizes, low temperature stars, and high nebular densities.
We have chosen a mixture of carbon-rich and oxygen-rich nebulae to see if
the wind properties are dependent on atmospheric chemistry. In addition, by
fitting the line profiles of some of the atmospheric lines, we can derive the
surface gravity and therefore obtain a better determination of the mass and
luminosities of the central stars.
================================================================================
Proposal Category: GO
Scientific Category: BINARY STARS
ID: 8305
Title: Two Post-Common-Envelope Binaries in the Hyades Cluster
PI: Howard E. Bond
PI Institution: Space Telescope Science Institute

V471 Tau and HZ 9 are two detached binaries that are members of the Hyades
cluster and consist of hot white dwarfs with main-sequence K-M companions.
They have emerged from common-envelope interactions which drastically reduced
their initially wide separations. For V471 Tau we will use STIS to confirm
and further explore the host of fascinating phenomena that we have found using
GHRS in a very limited spectral range near Lyman-Alpha. We have shown that the
white-dwarf component, which rotates with a 9.25-min period, has a polar cap
of accreted metals. The implied accretion rate from the dK wind, however, is
so low that a magnetic propeller mechanism must be rejecting most of the
material that attempts to accrete. In fact, we tentatively find Zeeman
splitting of a metallic line, implying a field strength of ~350 kG, sufficient
for the propeller mechanism to work. The GHRS radial velocities imply a white
dwarf mass of 0.85 M_\odot, paradoxically much too massive for the star's high
temperature. STIS, whose echelle can cover the entire UV spectrum from 1150-
1710 Angstrom, is ideal for confirming and extending all of these exciting
findings. We will also use STIS to obtain the first high-resolution UV
spectra of HZ 9, to see to what extent the above phenomena occur in a non-
magnetic system which is otherwise remarkably similar to V471 Tau, and to
determine accurate component masses.
================================================================================
Proposal Category: GO
Scientific Category: QUASAR ABSORPTION LINES
ID: 8306
Title: Lyman Alpha clouds toward PKS1302-102.
PI: Martin Lemoine
PI Institution: Departement d'Astrophysique Relativiste et de Cosmologie

We propose to conduct high spectral resolution (DeltaLambda~10 km/s)
observations of the low-redshift quasar PKS1302-102 (z_ em=0.278), whose line
of sight comprises ~20 Lyman Alpha absorbers with H i column densities in
excess of 10^14 cm^-2. Using existing archive FOS data of this quasar, we
derived constraints on the average ionization state and metallicity of the
absorbers. The constraint is not stringent because the FOS spectrum did not
fully resolve the absorption lines. However, when combined with existing upper
limits on the local metagalactic ionizing flux, it already suggests that these
low-z Lyman Alpha clouds are on average metal-deficient, with Fe/H<~-1. At
high resolution, the confidence region for the average radiation flux
intensity and metallicity would sharpen considerably and yield a reliable
estimate of these two physical characteristics; notably, this would yield an
estimate of the baryon content of Lyman Alpha clouds at low redshift.
Moreover, three intervening galaxies are present in the field, with impact
parameters spanning 40-200 kpc. This line of sight thus provides a unique
opportunity, for a relatively low observational cost, to study the morphology
and physical conditions of low-z Lyman Alpha clouds, whose nature and origin
remain unknown.
================================================================================
Proposal Category: GO
Scientific Category: STELLAR EJECTA
ID: 8307
Title: Morphology of High Radio Surface Brightness Planetary
Nebulae
PI: Sun Kwok
PI Institution: Department of Physics & Astronomy, University of Calgary

The morphological transformation from the spherically symmetric circumstellar
envelopes of AGB stars to the complex, bipolar structures of planetary nebulae
has remained one of the major unresolved problems in the late stages of
stellar evolution. Recent HST observations of proto-planetary nebulae and
planetary nebulae have found evidence for jets and radial filaments suggesting
that non-isotropic outflows are occuring during the early stages of planetary
nebula evolution. However, the morphology of very young planetary nebulae
have not been extensively studied by the HST. In this proposal, we have
selected a group of compact (< 2^ ) and high radio surface brightness
planetary nebulae to image in three narrow bands (HAlpha, N ii, and O iii)
to determine the morphological structures as a function of ionization. With
these images, we should be able to detect any previously unseen haloes, arcs,
jets, and knots, and derive the physical conditions of these features at the
earliest stage of PN evolution.
================================================================================
Proposal Category: GO
Scientific Category: BINARY STARS
ID: 8308
Title: The FUV Spectrum of SS 433
PI: Douglas Gies
PI Institution: Georgia State University

We propose to make the first ever investigation of the FUV spectrum of the
unusual X-ray binary, SS 433, using STIS and its sensitive MAMA detector.
The unexplored FUV region should offer significant clues about the nature of
the mass-losing star and mass loss by winds. Our plan is to obtain spectra at
key phases in the orbital and disk precessional cycles in order to document
the spectral variations associated with each of these ``clocks''. We will use
a tomography algorithm to separate the FUV spectral features associated with
the jets, disk and donor star, and we will compare the optical and FUV light
curves to establish the flux contributions from the various parts of this
system. Orbital phase variations in the UV P Cygni profiles will provide key
information on the role of colliding winds as a source of the X-ray flux.
The huge redshifts associated with the jets will translate jet flux from the
Lyman limit into the region near LyAlpha, and these variations will help
elucidate the radiative processes that drive the jets. The proposed
observations offer an exceptional opportunity to study the mass loss processes
at this singular stage in binary star evolution.
================================================================================
Proposal Category: GO
Scientific Category: HOT STARS
ID: 8309
Title: A Link Between Massive Binary Stars and Non-thermal Radio
Emission
PI: Debra Wallace
PI Institution: The Johns Hopkins University

Non-thermal radio emission in Wolf-Rayet (WR) stars is explained in terms of
synchrotron emission from shocks in the wind. For single star models, the
shocks arise from instabilities in the wind itself, whereas in binary models,
the shocks form at the wind-wind interaction zone. In Niemela et al. 1998
(from WFPC2 data), we support the binary theory, for two WR stars, linking the
non-thermal emission with the colliding wind region. Before we can
conclusively link non-thermal emission to binarity, we must demonstrate that
all non-thermal emitters are binary, and that all thermal emitters are either
single stars or binary systems with separations that are either too wide or
too close to result in a wind-wind interaction that produces shocks. We cannot
yet conclusively state this because WFPC2 does not resolve binaries with
separations less than about 0.100''. We propose to use the FGS to observe 9
non-thermal and 9 thermal WR stars to search for binary companions. The FGS
can resolve angular separations as small as .007''. If the non-thermal stars
are resolved as binaries and the thermal emitters are determined to be single,
the single star theory of non-thermal emission can be disavowed. Co-
latterally, we will have demonstrated a new method of detecting massive
binaries, and, for all WR stars, we will establish a more accurate binary
incidence rate.
================================================================================
Proposal Category: GO
Scientific Category: STELLAR POPULATIONS IN CLUSTERS
ID: 8310
Title: White Dwarf Distances to Globular Clusters and the RR
Lyrae Luminosity Calibration -- M5 and NGC 3201
PI: Andrew Layden^a
PI Institution: Bowling Green State University

Despite the efforts of Hipparcos, the RR Lyrae absolute magnitude
calibration, M_V(RR), remains uncertain at a level which critically
compromises these stars' use as standard candles. This uncertainty propagates
into globular cluster ages, Galactic formation scenarios, limits on the age of
the Universe, and estimates of the Hubble Constant. Reviewers have concluded
that fitting globular cluster white dwarf (WD) sequences to field WDs with
observed trigonometric parallaxes, or to theoretical WD cooling curves, has
the potential to provide a precise estimate of M_V(RR). However, data on WDs
in globular clusters are lacking. We propose deep HST WFPC2 imaging in F555W
and F814W of the WD sequences in two nearby globulars rich in RR Lyrae, NGC
5904 (M5) and NGC 3201. We describe our plans for the observations and
analysis, and estimate that our resulting M_V(RR) value will be accurate to
0.06 mag (random) plus 0.05 mag (systematic) -- more precise than existing
methods. We request parallel imaging observations using STIS to detect
variable stars in the cluster. We hope to discover and measure periods of
eclipsing contact binaries, which will provide an independent distance
estimate. We will also derive deep luminosity functions for these
intermediate metallicity globulars.
================================================================================
Proposal Category: GO
Scientific Category: DISTANT GALAXIES
ID: 8311
Title: MODERATE REDSHIFT ANALOGS TO LYMAN BREAK GALAXIES?
PI: Christopher Martin
PI Institution: California Institute of Technology

We propose to determine whether high luminosity galaxies selected using rest
ultraviolet luminosity at low-to-moderate redshift (0.2 Bright Galaxies UBG) are related to Lyman-break galaxies (LBGs) at high
redshift (3 limited samples selected at rest Lambda~ 1500Angstrom. This is the first
effort to make a systematic comparison of the high z population to a similar
luminosity class of galaxies at moderate redshift also selected in a flux-
limited photometric survey at the same rest wavelength. Study of these analogs
will provide a critical baseline for high z survey interpretation. Our
objective is to answer the following questions: 1. What is the star formation
rate in UBGs, the extinction correction, and how do these compare with the
LBGs? 2. What is the morphology and size of the UBGs, and how does this
compare with that of the LBGs? 3. Do the UBGs show evidence for prior episodes
of star formation, how does this compare to the prior star formation in the
LBGs, and how is this older population distributed? 4. Do the UBGs show
spectra similar to that of the high z sample? 5. Are the UBGs analogs to LBGs?
Ultimately, our objective is to test hierarchical structure models for galaxy
formation and evolution. We also propose test whether the Lyman continuum flux
escapes the galaxies.
================================================================================
Proposal Category: GO
Scientific Category: QUASAR ABSORPTION LINES
ID: 8312
Title: Low Column Density Ly-Alpha Absorbers at z=1.2: , High
SNR Echelle Spectroscopy of PG 1634+706
PI: Buell Jannuzi
PI Institution: National Optical Astronomy Observatories

We propose to produce the highest signal-to-noise ratio (SNR) Echelle
resolution spectrum ever obtained of Ly-Alpha absorbers between z=0.9 and 1.2
by augmenting the planned cycle 7 observations of the luminous quasar PG
1634+706 with five orbits of CVZ observing time with the E230M grating. Our
different central wavelength will allow a combined high SNR spectrum (>40 in
some regions) with 10 km s^-1 resolution that covers 1865 Angstrom to 3100
Angstrom. Recent theoretical work has shown that the neutral hydrogen column
density N_ HI of an absorber is tightly correlated with its overdensity, and
hence with its dynamical and physical state. However, the mapping between
overdensity and N_ HI changes as the universe expands. If we wish to study
absorbers at z~1$ that are physically similar to absorbers at z~3 we must
probe a factor ~20-50 lower in column density (Dave et al. 1998). The high
SNR spectrum obtained from our observations of PG 1634+706 will allow the
accurate (10\ uncertainties) measurement of the neutral column densities and
line profiles of lines with N_ HI as low as 3* 10^12 cm^-2 and the detection
of 87\ 2times10^12 cm^-2 for a significant path length. For the first time
it will be possible to study at z~1 the mildly overdense regions of the
intergalactic medium that have been observed so successfully at high redshift
(z~3) with HIRES and the Keck I telescope.
================================================================================
Proposal Category: SNAP
Scientific Category: CLUSTERS, LENSING AND COSMOLOGY
ID: 8313
Title: Imaging the Host Galaxies of High Redshift Type Ia
Supernovae
PI: Richard Ellis
PI Institution: Institute of Astronomy

We propose to obtain snapshot unfiltered STIS images of distant galaxies of
known redshift which have hosted supernovae (SNe) of Type Ia found via the
Supernova Cosmology Project. The Hubble diagram of these SNe yields
measurements of the cosmological parameters (Omega, Lambda) that are
inconsistent with a flat Universe of zero cosmological constant. Even if the
universe is not flat, Lambda > 0 is indicated with strong statistical
confidence (>99\ this confidence is now limited more by the possibility of
systematic errors than by statistical uncertainty. In particular, it is
important to justify convincingly that effects of the environments of low and
high redshift SNe are accounted for by current lightcurve width-color-
luminosity correction methods. HST will secure high resolution images to test
this hypothesis. We will look for correlations between the luminosity or
lightcurve width of the SNe and the host galaxy morphologies and positions of
SNe with respect to their host galaxies. We will identify a subset of SNe
that are far from the host galaxy, and thus likely to be un-extincted, and use
them to obtain an independent check on the effect of extinction on the
cosmological parameter measurements. Host galaxy morphologies will also
provide new constraints on possible evolution of the SN Ia rate as a function
of redshift and galaxy type which can be compared to predictions based on
global star formation histories.
================================================================================
Proposal Category: GO
Scientific Category: STELLAR POPULATIONS IN CLUSTERS
ID: 8314
Title: Star Clusters of NGC 6822
PI: Paul Hodge
PI Institution: University of Washington

We propose to obtain BVI photometry of four fields in the irregular Local
Group galaxy NGC 6822. The chosen fields include star clusters of a variety
of ages and we will study the CMDs of both the clusters and the surrounding
field stars. Our goals are: (1) to measure the oldest population of stars in
the field to answer the question of when star formation commenced in this
galaxy; (2) to ascertain the nature of the star formation history of the
galaxy; and (3) to look for evidence of a halo population of old stars.
================================================================================
Proposal Category: GO
Scientific Category: AGN HOSTS AND ENVIRONMENT
ID: 8315
Title: The Location of the Active Nucleus in the Radio Galaxy 3C
294
PI: Alan Stockton
PI Institution: Institute for Astronomy

We have obtained AO K'-band imaging of the z=1.779 radio galaxy 3C 294 showing
detailed and intriguing structure within a region a little larger than an
arcsecond across. Our bandpass corresponds to restframe 6800--8300 Angstrom,
a region devoid of strong emission lines, so it is likely that the structure
is dominated by continuum radiation. It is not obvious which (if any) of the
numerous knots corresponds to the nucleus, and the correct interpretation of
the structure depends critically on its location. The center of 3C 294 lies
about 9"\ from a V=12 star, and we know the registration of our image with
respect to this star to an accuracy of ~10 mas. Furthermore, the position of
the compact flat-spectrum radio core is known from VLA observations to a
similar or better precision. However, the position of the bright star is
uncertain by at least 0arcs8 (2 Sigma). We need to improve this uncertainty
by at least a factor of 6 in order to locate the nucleus with sufficient
precision in our image. We propose to use FGS1R to measure the position of the
star and three nearby V~15 stars with respect to a bright Hipparcos star,
which can be placed simultaneously in the FGS1R pickle. We will use
groundbased observations to determine more accurately the HST rotation angle
so that we can obtain both coordinates to the required accuracy from the
single astrometric standard.
================================================================================
Proposal Category: GO
Scientific Category: QUASAR ABSORPTION LINES
ID: 8316
Title: The LyAlpha Absorption Cross-Section of Nearby Galaxies
PI: David V. Bowen
PI Institution: Royal Observatory, Edinburgh

We propose to determine the size of Ly-alpha\ absorbing halos around nearby,
relatively isolated galaxies, by searching for Ly-alpha\ absorption in STIS
spectra of 12 UV-bright, background QSOs and AGNs. The galaxies selected cover
a range of luminosities, from M_B = -16.1 to -19.9, and are probed at
distances of 4-160 \h\ from their centers. We aim to settle the question of
whether galaxies possess extended, gaseous envelopes with radii of several
hundred kpc, and whether the presence of Ly-alpha -absorbing gas around a
galaxy depends on its luminosity, morphology, or inclination. To test the
latter case, for example, we have selected five sightlines which probe highly
inclined galaxies: three sightlines are aligned with the major axis of these
galaxies, the two others pass >= 45degrees away from the major axis. With
these data, we will be able to determine whether absorption occurs in galaxy
disks or halos. We wish to obtain spectra with the G140M grating to measure
precise column densities of the absorbing gas and thereby map the decline in H
I column density with galactocentric radius. The high resolution of the
spectra will allow us to accurately determine the velocity of the gas, which
can be compared to the systemic velocity of the galaxy, and to the velocity
field determined from 21 cm H I emission measurements, when available,
enabling us to determine if or how the gas is kinematically tied to the
galaxy.
================================================================================
Proposal Category: GO
Scientific Category: YOUNG STARS AND CIRCUMSTELLAR MATERIAL
ID: 8317
Title: Mass accretion rates for pre-main sequence intermediate
mass stars
PI: Nuria Calvet
PI Institution: Smithsonian Astrophysical Observatory

We propose to obtain the first direct, accurate measurements of mass accretion
rates for intermediate mass (1.5M(sun) to 3.5M(sun)) T Tauri stars (TTS),
precursors of the Beta Pic-type stars. Observations in the far and near
ultraviolet with the low resolution STIS spectrographs will be used to measure
the excess luminosity produced by the accretion of protoplanetary disk
material onto the central star. These measurements cannot be made at optical
wavelengths for these stars because of the lack of contrast between the excess
emission and the photospheric flux. These observations, combined with our
accretion shock column modelling, will provide for the first time
measurements of the mass accretion rate for intermediate mass TTS. With these
measurements and our existing infrared line fluxes, we will extend our present
calibrations of accretion luminosity with emission line luminosity for low
mass TTS to the entire range of mass covered by these stars. This will provide
a powerful tool for rapidly obtaining mass accretion rates for large samples
of stars in different evolutionary stages and environments, enabling the
effective study of stellar and protoplanetary disk formation and evolution.
================================================================================
Proposal Category: GO
Scientific Category: HOT STARS
ID: 8318
Title: Probing the Evolution of Massive Stars: Ejecta Ring
Nebulae Abundances and Dynamics
PI: Linda Smith
PI Institution: University College London

We propose to obtain STIS spectra of the nebulae surrounding several evolved
massive stars in the Magellanic Clouds. These stars represent a short but key
transition phase in the evolution of an O to a Wolf-Rayet (WR) star. This
phase is characterized by a sudden increase of the mass loss and the
appearance of processed material at the stellar surface. The remnants of this
brief period are seen as small circumstellar shells. Since the nebulae, in
effect, represent the stellar surface layers during the transition phase, the
stellar evolutionary history can be probed by using STIS spectra to measure
the N and O abundances together with the dynamics. HST is required because the
nebular radii are typically 2--4 arcsec and thus stellar contamination
precludes an accurate ground-based analysis. Our previous HST/FOS observations
show that one such nebula is not composed of heavily-processed wind material
but material that may have originated in a RSG envelope. Since our findings
directly challenge our understanding of the evolution of massive stars and
their enrichment of the interstellar medium through extensive mass loss, we
propose to undertake a systematic abundance study of nebulae around evolved
massive stars. This study will allow us to understand at which evolutionary
stage the major mass loss occurs in the transition from an O to a WR star, and
provide new insights into the LBV mass loss mechanism.
================================================================================
Proposal Category: GO
Scientific Category: YOUNG STARS AND CIRCUMSTELLAR MATERIAL
ID: 8319
Title: Masses and Distances of Pre-Main Sequence Binaries
PI: Michal Simon
PI Institution: SUNY

We propose the continuation of FGS measurements of the orbital motion of young
stars successfully carried out in Cycle 7 and earlier cycles. We need to
continue these observations to acquire sufficient data to determine the
orbital parameters of the binaries. Our goal is to measure the masses of low
mass young stars. This will enable a calibration of theoretical calculations
of stellar evolution to the main sequence. Hipparcos measured the distance
41+/-10 pc to one of our program binaries, DF Tau, making it an isolated T
Tauri star, much closer than its presumed location in the Taurus star forming
region at ~ 150 pc (Favata et al. 1998, F98). This measurement drastically
changes the conventional interpretations of DF Tau's evolutionary state and
its activity. An independent confirmation is urgently required. DF Tau lies
well within the capabilities of a reliable parallax measurement using the FGS.
We therefore propose parallax measurements of DF Tau and two other binaries in
Taurus in our sample.
================================================================================
Proposal Category: GO
Scientific Category: INTERSTELLAR AND INTERGALACTIC MATTER
ID: 8320
Title: The H_2/CO ratio in the Large Magellanic Cloud
PI: Dominik J. Bomans
PI Institution: Astronomisches Institut, Universitaet Bochum

Little is known about real abundance ratios of the two most abundant molecules
H_2 and CO in the interstellar matter of the Large Magellanic Cloud. Because
of their abundance, both molecules play a crucial role in the physics of
molecular gas. The only possibility to observe the homoeopolar molecule H_2
in its cool phase is the measurement of its far UV resonance lines with
absorption spectroscopy., So far, of 4 observed lines of sight to the LMC,
only the one to LH 10:3120 showed a significant amount of the H_2 molecule at
LMC velocities. The CO molecule also has resonance lines in the far UV, but
due to its much smaller amount and the relatively poor signal to noise ratio
in the ORFEUS spectrum of LH 10:3120, the presence of CO could not be
established from those measurements., With its high resolution spectrograph
(STIS), the Hubble Space Telescope provides the possibility to measure several
strong CO absorption bands near 1500 Angstrom\ due to the LMC gas. We propose
to observe LH 10:3120 and make the direct determination of the H_2/CO ratio
for the LMC possible for the very first time.
================================================================================
Proposal Category: GO
Scientific Category: AGN PHYSICS
ID: 8321
Title: Coordinated STIS/AXAF Spectroscopy of UV/X-ray Absorption
in the Seyfert 1 Galaxy NGC 4051
PI: Niel Brandt
PI Institution: The Pennsylvania State University

X-ray studies of the nearby Seyfert 1 galaxy NGC 4051 reveal strong and
complex absorption by ionized nuclear gas (a `warm absorber'). This gas is a
major component of the nuclear environment, and we will soon use AXAF to make
the first grating-resolution study of the X-ray warm absorber in NGC 4051.
Here we propose simultaneous or near-simultaneous STIS UV spectroscopy. Many
Seyferts/quasars with X-ray warm absorbers also show UV absorption lines (e.g.
LyAlpha, N v and C iv), and it has been argued that the X-ray and UV
absorption arise in the same gas. NGC 4051 shows evidence for C iv
absorption in IUE spectra, and combined STIS/ AXAF spectra will allow us to
critically test the unified UV/X-ray absorber model by comparing the velocity
fields and strengths of the UV/X-ray absorption. We will also derive superior
constraints upon the internal velocity structure, location, global covering
factor, and line-of-sight covering factor of the ionized gas. NGC 4051 is a
particularly interesting target because, as a soft X-ray `Narrow-Line Seyfert
1' galaxy, its ionizing continuum is substantially softer than that of more
`typical' Seyfert 1s (e.g. NGC 3516 and NGC 3783). This may lead to
significantly different absorption characteristics. This observation will be
the first HST UV spectroscopy of NGC 4051, and simultaneous observations are
important because the absorption is likely to be variable.
================================================================================
Proposal Category: GO
Scientific Category: CLUSTERS, LENSING AND COSMOLOGY
ID: 8322
Title: The Distance to NGC 2841: Improving the TF Calibration
and Definitively Testing MOND
PI: Greg Bothun
PI Institution: University of Oregon

This proposal aims to measure a distance to the spiral galaxy NGC 2841 using
Cepheid variables. NGC 2841 provides a unique opportunity to simultaneously
probe three separate phenomenon in extragalactic astronomy: 1) It will provide
the highest rotational velocity data point for the Cepheid based calibration
of the I-band Tully-Fisher relation and thus will firmly determine if this
relation experiences curvature or remains linear all the way out to high
rotational velocities. 2) It has hosted two SN Ia events; both of which have
good photometry (1957A and 1972R)- this significantly adds to the number of
calibrators for the SN Ia distance scale; 3) If its distance can be shown to
be significantly less than 19.5 MPC, then MOND can be definitively ruled out
because NGC 2841 will require a value of a_o substantially in excess of the
empirically determined "universal" value. The current estimated distances for
NGC 2841 range from 9--20 Mpc. An accurate determination of this distance,
based on HST detection and measurements of its Cepheids, will therefore have
an important and distinctive impact in these three areas.
================================================================================
Proposal Category: GO
Scientific Category: STELLAR EJECTA
ID: 8323
Title: Herbig-Haro Jets Irradiated by Massive OB Stars
PI: John Bally
PI Institution: CASA, University of Colorado, Boulder

Despite significant recent advances in the investigation of Herbig-Haro jets
powered by young stars, a number of fundamental problems remain unsolved.
Among these are the precise determination of the mass loss rate through a
jet, and the nature of the flow behavior in the jet launch and collimation
region. We have discovered a class of HH jets which are irradiated by the UV
radiation from nearby OB stars and are therefore photoionized. Such jets hold
the promise of a direct measurement of the mass flow rate through a jet.
Furthermore, our observations show that the opaque envelopes that normally
obscure jet sources have been removed from these objects. We propose to use
HST to study the brightest of these irradiated jets, HH 444. STIS spectra
will be used to measure the distribution of electron density, the mass flux
through the jet, and the kinematics and excitation conditions in or near the
jet collimation region which will constrain models of jet formation. We will
also use WFPC2 to determine the sub-arcsecond structure of the jet so that we
can correctly interpret the STIS spectra, to search for evidence of a
circumstellar disk needed to fuel the jet, and to probe the nature of the
asymmetry seen in this jet.
================================================================================
Proposal Category: GO
Scientific Category: YOUNG STARS AND CIRCUMSTELLAR MATERIAL
ID: 8324
Title: The Structure and Kinematics of Irradiated Disks and
Associated High Velocity Features in Orion
PI: John Bally
PI Institution: University of Colorado, Boulder

STIS provides us with a unique opportunity to study the early evolution of
proto-planetary disks and their chances of survival in the harsh irradiated
environments of OB associations where most stars form. We seek to test new
circumstellar disk photo-erosion models for the Orion Nebula proplyds (proto-
planetary disks), to measure the disk mass loss rates, the nature of their
tails, and the high excitation upstream bow shocks (HAlpha + ionO3 arcs). We
will obtain long-slit low dispersion UV spectra to measure the relative
intensities of a variety of UV lines that trace the excitation conditions in
the circumstellar disk, neutral outflow, and in the ionized zone and to search
for OH emission predicted by a recent model of photo-chemical excitation of
the 6300Angstrom\ ionO1 line. We will obtain moderate resolution long slit
visible spectra to constrain the sub-arcsecond structure and excitation
conditions in the proplyds, search for disk rotation, estimate disk wind
velocities, and measure the flow velocities as a function of position,
excitation, and ionization and in various portions of the photo-ablation flow.
We will measure the velocity fields of several supersonic micro-jets powered
by the Orion proplyds. Our data will constrain the survival time of
irradiated disks, address their potential for forming planetary systems, and
shed light on the planetary system formation frequency.
================================================================================
Proposal Category: GO
Scientific Category: CLUSTERS, LENSING AND COSMOLOGY
ID: 8325
Title: Galaxy Evolution in Low-Density Environments: WFPC2
Imaging of Poor X-ray Clusters at z=0.2--0.3
PI: Roger Davies
PI Institution: University of Durham

We propose to use WFPC2 to obtain high quality morphological information on
galaxies within 9 X-ray-selected poor clusters at z=0.2--0.3. These
morphologies will be combined with information on the stellar populations of
the galaxies from our on-going spectroscopic survey of these systems to
provide a complete view of the morphological and spectral evolution of
galaxies within these clusters. The results of this analysis will be
contrasted with the conclusions of previous HST/spectral studies of much
richer clusters to provide a clearer understanding of the physical processes
which operate on galaxies and how these vary with environment. One Specific
goal is to test recent claims that the ram-pressure of the intra-cluster
medium causes a morphological and spectroscopic transformation of star forming
disk galaxies into S0 galaxies.
================================================================================
Proposal Category: GO
Scientific Category: STELLAR EJECTA
ID: 8326
Title: Colliding stellar winds and proto-planetary dynamics:
WFPC2 imaging of OH231.8+4.2
PI: Valent'\in Bujarrabal
PI Institution: Observatorio Astronomico Nacional

The interaction between a fast post-AGB collimated wind and a slowly
expanding, dense AGB wind is believed to be the dominant dynamical effect in
the evolution of protoplanetary nebulae (PPNe) and the shaping of planetary
nebulae. We are carrying out a multi-wavelength study of the protoplanetary
nebula OH231.8+4.2. Our interferometric mapping of mm-wave molecular lines in
OH231.8+4.2 shows the presence of a massive molecular envelope, to which a
large amount of momentum has recently been transferred via shock interaction.
Long-slit optical spectroscopy reveals the overall kinematics of the shocked
high-excitation gas, showing a strong axial gradient superimposed on bubble-
like expansion. OH231.8+4.2 is the only PPN known so far in which the leading
bow shock has been detected. Because of the rich structure of the shocks in
this source, it is the best candidate to study protoplanetary dynamics, but
the different components are still poorly resolved in present observations. We
propose to use HST/WFPC2 to image with high angular resolution the atomic
line emission from the gas component excited by shocks in OH231.8+4.2. These
observations will enable an accurate determination of the structure and
excitation stratification of the shock fronts and, we argue, will lead to
major advances in our understanding of the dynamics of colliding stellar winds
and their effect on protoplanetary evolution.
================================================================================
Proposal Category: GO
Scientific Category: HOT STARS
ID: 8327
Title: STIS observations of Eta Carinae: The central star
PI: Kris Davidson
PI Institution: University of Minnesota

Eta Carinae relates to a number of astrophysical topics and may be crucial for
some of them, but its physical nature is certainly Not Yet Understood, and in
1998 the research situation became even more extraordinary than it was before.
New STIS observations had the combination of good spatial and spectral
resolution, with UV-to-far-red wavelength coverage, that we've always wanted
for studies of the star itself (or its wind). However, these data were
acquired during a major ``spectroscopic event.'' It has now become clear that
such events recur at 5.5-year intervals, strongly affect the X-rays, and, as
the STIS data show, are not easy to explain. Given a 5.5-year periodicity, the
binary-vs.\-single-star question has become critical for further progress on
Eta Car. If it is a binary, we need to find the parameters. STIS spectroscopy
of Eta's normal state is required. Here we propose a project with several
combined goals: (1) to obtain the spectrum of the star at ``normal'' times;
(2) to extend the wavelength coverage below 1700 Angstrom; (3) to seek
evidence for a hypothetical companion star; (4) to learn whether Eta Car
varies significantly when it is not near a discrete spectroscopic event; and
(5) to study the bizarre spectra of dense, slow-moving, extremely peculiar
ejecta located 0.15" to 1.5" from the star. This project is coordinated with
our Cycle 7 program and some planned GTO observations.
================================================================================
Proposal Category: GO
Scientific Category: HOT STARS
ID: 8328
Title: HST ASTROMETRY TO GAUGE THE DISTANCE OF PSR0833-45 (VELA)
and PSR 0656+14
PI: Patrizia Caraveo
PI Institution: Istituto di Fisica Cosmica del CNR

High angular resolution, coupled with sensitivity, makes HST the ideal
instrument to measure tiny displacements of faint objects, such as those due
to proper motions and annual parallaxes of Isolated Neutron Stars. ,In this
proposal, we first include the third exposure of the Vela pulsar aimed at the
measure of its parallactic displacement (see GO 6526), then we ask for two
more exposures for PSR 0656+14, for which one PC observation, close to the
time of the maximum parallactic displacement, is already in hand (GO 6136).,
The distance value of both objects is highly disputed and a model-free
measurement (or a reliable lower limit) would be very important, e.g., to
assess the luminosity of these objects at different wavelengths and measure
how efficienctly they convert their rotational energy losses in optical, X and
gamma radiation.
================================================================================
Proposal Category: GO
Scientific Category: BINARY STARS
ID: 8329
Title: Double Degenerates Among DAO White Dwarfs
PI: Matthew Burleigh
PI Institution: University of Leicester

The evolution of DAO white dwarfs, which have hybrid spectra showing both
hydrogen and helium lines, is not well understood. It appears that they may be
a rather disparate collection of objects with a variety of different origins.
For example, it was recently discovered that one of these stars (Feige 55)
lies in a close double degenerate system, and must therefore have undergone
mass transfer and common envelope evolution. We propose to obtain STIS/FUV
spectra of two problematic DAOs, GD561 and PG 1210+533, to determine whether
they are also the product of binary evolution. Circumstantial evidence exists
to suggest that both stars possess unresolved degenerate companions. However,
ground based observations to search for radial velocity variations have proved
inconclusive, since the H Balmer lines in these hot stars (50,000K are too broad and shallow to allow accurate velocity determinations, even with
the largest telescopes available. Indeed, PG 1210+533 in particular shows no
sharp NLTE cores from which precise measurements can be made. Instead, we
propose to utilise narrow heavy element lines in far-UV spectra (e.g. CIV).
Using a similar observing strategy to ground-based searches for double
degenerates, we will observe each star on two successive HST orbits (i.e.
separated by ~2 hours), followed by a further observation one day later, to
cover as many potential periods as possible.
================================================================================
Proposal Category: GO
Scientific Category: STELLAR EJECTA
ID: 8330
Title: High Resolution Imagery of Selected Symbiotic Stars
PI: Michael Bode
PI Institution: Liverpool John Moores University

A fuller understanding of the symbiotic star phenomenon is important to
several branches of astrophysics including mass loss, accretion onto compact
objects, and photoionisation and radiative transfer in gaseous nebulae. Our
work with MERLIN, the VLA and the AT has revealed complex structure down to
sub-arcsecond spatial scales, similar to the proposed binary separation in
some objects. Combining the surprisingly limited amount of HST imaging data
that currently exists with our radio observations has demonstrated the
potentially important gains in understanding to be made. The aims of this
proposal are (i) to help define the positions of the binary components in our
targets (crucial to deeper understanding of the sources); (ii) to relate
structure on various spatial scales to the history of activity and other
parameters of each source (e.g. to explore collimation mechanisms for jets and
to determine distances by expansion parallax); (iii) to explore physical
conditions in the inner nebulae and perform extinction mapping; (iv) compare
and contrast the properties of sub-classes of symbiotic, and (v) to prepare
the ground for future STIS spectroscopy. Our target list contains the four
objects for which we have the largest amount of ground-based data, and for
which structure on sub-arcsecond scales has been revealed by our radio
observations. Between them, they represent intriguing examples of both major
sub-classes of symbiotic.
================================================================================
Proposal Category: GO
Scientific Category: DISTANT GALAXIES
ID: 8331
Title: Probing the Dark Side of Galaxy Formation: HST Imaging of
the ISO ULTRADEEP Survey
PI: David Clements
PI Institution: Institut d'Astrophysique Spatiale & Cardiff University

The Hubble Deep Field (HDF) gave us an unprecedented view of the optical and
rest--frame--UV side of galaxy formation. However, new data from ISO and COBE
confirms the suspicion that the optical/UV does not tell the whole story. ISO
observations have also demonstrated that this is true even in the HDF. These
show the presence of ~25 galaxies brighter than ~200MuJy at 15Mum. However, it
is so far unclear what distinguishes the ISO sources in the HDF from many
similar HDF galaxies undetected by ISO. There is a suggestion that they are
more often interacting systems, and that they have somewhat redder colours,
but at this stage the sample size in the HDF is too small to draw definitive
conclusions. We thus propose obtaining moderately deep (~ 24-25 mag arcsec^-
2) imaging of the ISO ULTRADEEP survey region. This survey covers 25 arcmin^2
to a 75MuJy flux limit -- larger and deeper than the ISOHDF -- and includes
~200 sources to the 3Sigma flux limit -- nearly 10 times as many as found by
ISO in the HDF. With our much larger sample we will examine the detailed
morphologies, colours and colour-distributions and compare them with objects
undetected by ISO. In this way we will determine what makes a galaxy mid-IR
luminous, and thus uncover the origin of the strong evolution seen in this
population. This will put us one step closer to understanding the dark side
of galaxy formation.
================================================================================
Proposal Category: SNAP
Scientific Category: STELLAR EJECTA
ID: 8332
Title: A Snapshot Survey of Symbiotic Stars
PI: Michael Bode
PI Institution: Liverpool John Moores University

A fuller understanding of the symbiotic star phenomenon is important to
several branches of present day astrophysics including mass loss, accretion
onto compact objects, and photoionisation and radiative transfer in gaseous
nebulae. Optical imaging has been used to great effect in combination with
observations at other wavelengths, and the detailed history of variability of
sources, to determine such fundamental parameters as distances, likely jet
collimation mechanisms and evolutionary links to the formation of planetary
nebulae. That said, there is a dearth of high spatial resolution imaging of
these objects with the HST. This is despite the fact that our own radio
interferometry has shown structure down to sub-arcsecond size scales where in
many cases one is sampling regions with dimensions of order that of the
central binary pair. Here we propose to conduct the first HST survey of a
carefully selected sample of symbiotics covering all major sub-types. As this
is an exploratory programme, requiring relatively short exposures, we have
chosen to conduct it in SNAPSHOT mode.
================================================================================
Proposal Category: GO
Scientific Category: GALAXY POPULATIONS AND INTERACTIONS
ID: 8333
Title: Pox 186: A Nearby Protogalaxy?
PI: Michael Corbin
PI Institution: Steward Observatory

Blue Compact Dwarf Galaxies (BCDGs) typically consist of clusters of early-
type stars embedded in older, evolved stellar populations similar in size and
shape to normal dwarf ellipticals. However, deep ground-based CCD images of
one faint BCDG, Pox 186, reveal a very compact (~ 5" diameter) structure with
no evidence of an underlying older population. Optical spectroscopy of this
object also indicates that a large number of Wolf-Rayet stars are present,
which implies that a burst of star formation must have occurred very recently
(<=sssim 10^7 years ago). It has thus been suggested that Pox 186 is a
protogalaxy, forming its very first generation of stars. Further
investigation of this possibility requires the high angular resolution and
ultraviolet spectral coverage that only HST can provide. Using WFPC2, we
propose to image the galaxy in the U, V, and I bands, in order to better test
for the presence of an underlying evolved population and to revea
================================================================================
Proposal Category: GO
Scientific Category: YOUNG STARS AND CIRCUMSTELLAR MATERIAL
ID: 8334
Title: HD 98800: An Opportunity to Measure True Masses for Low-
Mass PMS Stars
PI: David Soderblom
PI Institution: Space Telescope Science Institute

HD 98800 became interesting when IRAS found it to have a large infrared
excess, indicating a substantial dust disk. But ``HD 98800'' is, in fact, a
quadruple system consisting of four K and M stars, and its Hipparcos parallax
has now shown that this is a pre-main sequence system. The four stars are in
two visible objects, each of which is a spectroscopic binary with a period of
about one year. In particular, the Ba-Bb pair is an SB2 with an estimated
semi-major axis of about 20 milliarcsec. In TRANS mode, FGS1R can cleanly
resolve the Ba-Bb pair and can determine the relative orbit and luminosities
for the two components. POS mode observations lead to an absolute orbit and a
more precise parallax than is currently available. In this program we propose
to follow the HD 98800 Ba-Bb pair over the course of a full orbit during Cycle
8. The combination of FGS1R-TRANS and FGS1R-POS observations will provide
gravitational masses for two low-mass PMS stars. In addition, the constraints
of coevality and knowledge of the astrophysical properties of the components
(temperatures, luminosities, composition) make these observations a crucial
test of our models of pre-main sequence evolution. These may be the first
true masses determined for low-mass PMS objects, and so can provide a
fundamental test of PMS evolutionary tracks.
================================================================================
Proposal Category: GO
Scientific Category: CS
ID: 8335
Title: Calibrating Stellar Models with the Pleiades: Resolving
the Distance Discrepancy
PI: David Soderblom
PI Institution: Space Telescope Science Institute

This is the first phase of a multi-year effort to measure true masses for low-
mass dwarfs in the Pleiades and to determine an accurate distance to this
fundamental cluster. The goals are: 1) To determine the true distance to the
Pleiades to resolve the problem raised by the Hipparcos results for this
cluster. The Hipparcos distance for the Pleiades, taken at face value,
indicates that solar-composition ZAMS stars are 30\ 2) To test ZAMS models of
evolution for young solar-type stars by measuring masses of individual stars.
3) To construct a mass-luminosity relation for young low-mass stars with solar
composition. The resolution to the Hipparcos distance problem is vital for
understanding all the parallaxes that have come from that mission and hence
this issue is fundamental to the cosmic distance scale. In this first phase
we get several observations of three systems which are already resolved
spectroscopically and which have 2 to 3 year orbital periods, and we examine
other Pleiades binaries to ascertain which objects are resolvable pairs with
separations suitable for orbit determinations with the FGS. Please note: Most
of our targets are bright and near each other, and can therefore be surveyed
in TRANS mode in 1/2 an orbit each. Our total orbit request reflects this.
================================================================================
Proposal Category: GO
Scientific Category: QUASAR ABSORPTION LINES
ID: 8336
Title: A Unique Measurement of the Dust-to-Gas Ratio in an
Absorption Line Systems
PI: Ross Cohen
PI Institution: University of California, San Diego

The dust--to--gas ratio in damped Ly-alpha\ absorbers has been determined from
ISM metal abundances and from the effect of extinction on the background
quasar continuua. Both methods have significant uncertainties. A damped
system lies along the line--of--sight to both bright components of the
gravitationally lensed quasar, 0957+561. If we observe the complete UV to
optical spectrum of each component separated in time by the known time delay
in this system, we can make a differential measurement of the reddening which
does not depend on the intrinsic continuum shapes. This will yield a precise
measurement of the dust--to--gas ratio in an absorption system at redshift
z=1.3911 and will test whether the extinction laws of the Galaxy and
Magellanic clouds are the same as those in extragalactic systems. We can also
test our assumptions about how abundance measurements translate into dust--to-
-gas ratios by comparing these results with dust--to--gas ratios derived using
high--resolution spectra of both components obtained at Keck Observatory. The
UV portion of these observations is required to discriminate between different
extinction laws and clearly requires HST. Because the extinction in the
optical is lower, very high accuracy in the relative flux calibration of the
two objects is required. This accuracy is not attainable from the ground
because of cross--contamination of the two spectra and contamination by the
lensing galaxy.
================================================================================
Proposal Category: GO
Scientific Category: GALAXY POPULATIONS AND INTERACTIONS
ID: 8337
Title: Red Giants, Planetary Nebulae, and the Properties of
Virgo's Intracluster Stars
PI: Robin Ciardullo
PI Institution: The Pennsylvania State University

Intracluster starlight can be a powerful probe of the structure and
evolutionary state of galaxy clusters. Recently, this field of study has been
revolutionized by the ground-based discovery of intracluster planetary nebulae
(IPN) in the Virgo and Fornax Clusters, and by the detection of Virgo's
intracluster red giants (IRG) by HST. These two measurements should
complement each other: ground-based IPN surveys can map out the distribution
and kinematics of the intracluster stars, while HST IRG measurements at
specific locations in the cluster can provide details about the stellar
population and normalize the IPN data. Unfortunately, the IPN and the IRG
observations to date are not complementary. The distribution of intracluster
stars in Virgo is clumpy, and the HST IRG field has the misfortune to be
located in a region of very low stellar density. Since very few IPN are
located in the field, we cannot compare their luminosity function to that of
the red giants. We propose to use the Hubble Space Telescope to detect IRG
stars in regions of the Virgo cluster where the stellar density is high and
the IPN luminosity function is well defined. These observations will allow us
to calibrate IPN measurements in the rest of the cluster, independently
confirm the Virgo Cluster morphology, and place new constraints on the parent
populations of the intracluster stars.
================================================================================
Proposal Category: GO
Scientific Category: AGN HOSTS AND ENVIRONMENT
ID: 8338
Title: The Evolution of the Host Galaxies of Powerful Radio
Sources
PI: Matthew Lehnert
PI Institution: Sterrewacht Leiden

The co-moving space density of highly luminous AGN has decreased by roughly 3
orders of magnitude from z=2-3 to the current epoch. To enhance our
understanding of this ``mass extinction'' of luminous AGN, we propose to
conduct a broad-band imaging survey, using the WFPC2, of 20 radio galaxies
with a large range of redshifts (~0.3 to 3), and radio powers and
morphologies, selected from a complete sample of radio sources. Continuum
filters are chosen such that galaxies at all redshifts are imaged at constant
rest-wavelength near 2200Angstrom, in a region free of strong emission lines.
Imaging of this type over such a wide range of redshifts has never been
attempted before. These data will allow us to study the properties and
evolution of radio galaxies at uniform wavelength over look-back times of 25
to 85\ the universe. Our recent studies of a similarly selected sample of
radio-loud quasar hosts have shown that the rest--frame UV luminosities of the
host galaxies increase by about a factor of 100 between z=0.3 and z=3, and
that the higher redshift hosts have larger sizes and more distorted
morphologies. A combined data set of radio galaxies and quasars will allow
powerful tests of the relationship between radio galaxies and quasars and the
evolution of the host galaxies of powerful radio sources over a wide range of
look-back times.
================================================================================
Proposal Category: GO
Scientific Category: STELLAR POPULATIONS IN CLUSTERS
ID: 8339
Title: Light Element Abundance Variations in the Core of 47
Tucanae
PI: Michael Briley
PI Institution: University of Wisconsin-Madison

We propose a novel use of the F390N and F410M WFPC2 filters to explore the
extent of star-to-star light element variations in the core of the Galactic
globular cluster 47 Tucanae. Observations in 47 Tuc have revealed that large
star-to-star differences in sodium, correlated with CN band-strength
differences, exist amoung its main-sequence turn-off stars, well before any
proposed mechanism for Na production and subsequent mixing could be in
operation. Moreover, the range of Na abundances and CN band-strengths
observed at the turn-off are consistent with those found among the evolved red
giants of 47 Tuc. The simplest interpretation of this result is that the gas
from which the present cluster stars formed was inhomogeneous in at least C,
N, and Na. The ratio of CN-enhanced to CN-normal stars is also found to
increase by a factor of 3 from a radial distance of 17' to 10'. The ratio
of CN-enhanced to CN-normal stars is unknown within a radial distance of 4'
due to crowding. This segregation in CN distribution carries evidence of the
chemical and dynamical processes which created these inhomogeneities. Probing
this signature into the very core of the cluster will provide tighter
constraints on possible origins of the chemical inhomogeneities and,
ultimately, on the early history of the globular clusters. The superior
imaging capabilities of HST will allow us to probe much closer into the dense
core of 47 Tuc.
================================================================================
Proposal Category: GO
Scientific Category: AGN PHYSICS
ID: 8340
Title: Probing the Kinematics of the Narrow-Line Region, in
Seyfert Galaxies with Slitless Spectroscopy
PI: D. Michael Crenshaw
PI Institution: Catholic University of America

Studies of the gas kinematics of the narrow-line regions (NLRs) in Seyfert
galaxies indicate complex velocity fields, with evidence for both
gravitational and non-gravitational forces. Determining the relative
importance of these dynamical effects as a function of position will shed
light on: 1) the mass of the putative supermassive black hole (SMBH), 2) the
interaction of jets and/or outflowing winds with the NLR gas, and 3) the
fueling of the active nucleus from gas in the NLR and surrounding galaxy.
Slitless spectroscopy with STIS is an exciting new technique, which will allow
us to determine the velocity field of the entire NLR in a single orbit. We
will obtain slitless G430M spectra of the extended O III Lambda5007 emission
in 14 Seyfert galaxies, at a spectral resolution of Lambda/DeltaLambda ~
10,000 and a spatial resolution of 0"point1 -- 0"point2. A survey of this size
is necessary to investigate the relationship between the kinematics and other
properties, including morphology of the NLR, orientation effects, prominence
of radio jets, and extranuclear characteristics. Based on our experience with
STIS slitless spectra of NGC 4151, we have selected targets that show
prominent O III knots of emission, to ensure the success of this technique and
to complement observations of compact or smooth NLRs that require a long slit.
================================================================================
Proposal Category: GO
Scientific Category: AGN PHYSICS
ID: 8341
Title: UV Spectroscopy of M33-X8: mini-AGN or black-hole binary?
PI: Phil Charles
PI Institution: Oxford University

The nucleus of M33 contains X-8, the most luminous steady X-ray source in the
Local Group (Long et al, 1996). Our ROSAT long-term studies (Dubus et al,
1997) have shown that it exhibits a remarkable 106d periodicity which is
similar to the ``super-orbital'' modulations seen in some galactic low-mass X-
ray binaries. This indicates that X-8 is a single object, and our recent
WFPC2 UV images reveal a ~16th magnitude UV source in the centre of the
(almost) stellar M33 nucleus. However, the nature of this object cannot be
gleaned from optical studies as the nucleus is dominated by a compact stellar
core of ~F integrated spectral type. And with an L_X/L_UV ratio much too low
to be typical of an X-ray binary (unless it is an accretion disc corona
source), X-8 is likely to be the nearest example of a ``mini-AGN''. We are
therefore applying for STIS far-UV to optical spectroscopy to study this
potentially crucial link between X-ray binary behaviour (the periodicity) and
that of AGN.
================================================================================
Proposal Category: GO
Scientific Category: CS
ID: 8342
Title: ABUNDANCES IN HALO STARS AND GALACTIC ELEMENT FORMATION
PI: John Cowan
PI Institution: University of Oklahoma

We propose to measure the abundances of a wide array of elements ranging from
light neutron-capture elements (such as germanium) up to the very heaviest
such elements (including platinum and lead) in a number of very old, metal-
poor halo stars. These elements, synthesized in stellar interiors by r(apid)
and s(low) neutron capture processes, had, until our very recent successful
detections in Cycles 5 and 6, never before been observed in metal-poor stars
because their only strong lines lie in the ultraviolet spectral region. The
abundance data of both the lighter and heavier neutron-capture elements in the
same stars will be critical to an understanding of the early star formation,
nucleosynthetic history and associated chemical evolution of our Galaxy.
Employing the HST data of the most massive stable elements to define the
initial abundances of the radioactive elements (particularly thorium), we will
also determine the chronometric (radioactive-decay) ages of our target stars,
and thus define an actual age-metallicity relationship for the halo stars in
the Galaxy. Our results for the very oldest Galactic stars will also provide
an important, and independent, age determination for the Galaxy and hence
constrain cosmological age estimates.
================================================================================
Proposal Category: GO
Scientific Category: BINARY STARS
ID: 8343
Title: Structure and evolution of the globular cluster low mass
X-ray binary AC211 in M15
PI: Phil Charles
PI Institution: University of Oxford

Our Cycle 7 STIS UV spectra of AC211, the optical counterpart of the bright X-
ray binary X2127+119 in the core of M15, have revealed strong HeII Lambda1648
and CIV Lambda1550 emission together with many broad absorption lines
including LyAlpha. The temporal information through primary eclipse will
enable us to map the disc and wind of this accretion disc corona source.
Recently Homer & Charles (1998) have shown that the 17.1 hr X-ray light curve
is stable on long timescales and reveals secondary dip structure around phase
0.5 which we presume to be associated with the disc rim. We are therefore
proposing here for additional time-resolved UV spectrophotometry covering
phases 0.15-0.7 so as to investigate the complex interaction of the mass
transfer stream with the accretion disc. AC211 is optically the most luminous
of all the globular cluster X-ray sources and, with its high inclination, is
the ideal object for such a study.
================================================================================
Proposal Category: GO
Scientific Category: FIELD STELLAR POPULATIONS
ID: 8344
Title: UV Spectral Properties of O and B Stars Versus
Metallicity
PI: Frederick Bruhweiler
PI Institution: Institute for Astrophysics & Computational Sciences

Metallicity is the most fundamental parameter governing both stellar and
galactic evolution. Yet, little is known observationally about how metallicity
affects the physics of massive stars. To explore this connection, we will use
the STIS to obtain slitless UV spectroscopy of bright OB associations in three
Local Group galaxies that span a factor of 30 in metallicity. Our targets are
star-forming regions in M31, NGC 6822, and Sextans A. Nebular O/H abundances
indicate Sextans A is the most metal deficient galaxy in the Local Group, with
a metallicity 30x below the Galaxy and 3x below the SMC. The STIS UV slitless
spectra will resolve numerous O and B stars in a single exposure. This study
will use the unique spectral imaging capabilities of STIS to probe stellar
populations spanning the widest range of metallicity possible. Theoretical
synthetic spectra will be constructed in an attempt to match the strengths and
shapes of both strong photospheric and wind features. In this way we will
derive approximate abundances, mass loss rates, and terminal velocities. We
will also apply our new UV stellar classification criteria and probe the
variation with metallicity of mass-loss characteristics through the H-R
diagram. Our goal is to answer one of the most fundamental questions in
astrophysics: ``What is the impact of chemical abundance upon stellar mass
loss?"
================================================================================
Proposal Category: SNAP
Scientific Category: STELLAR EJECTA
ID: 8345
Title: Multipolar Bubbles and Jets in Very Low Excitation
Planetary Nebulae - A WFPC2 HAlpha imaging survey
PI: Raghvendra Sahai
PI Institution: Jet Propulsion Laboratory, California Institute of
Technology

Planetary nebulae (PNe) show a dazzling variety of structures not apparent in
the circumstellar envelopes of the AGB stars from which they evolve. The
physical phenomena which shape the PNe occur early in their formation history,
involving the hydrodynamic interaction of one or more fast winds with the
slower AGB mass-outflow. However, since the youngest PNe, which retain the
clearest visible signatures of these phenomena, are very compact (<5''),
ground-based observations provide very limited information on these objects.
Our Cycle 6 H Alpha imaging survey of very young, low-excitation PNe showed
that all 11 objects imaged have extreme aspherical structure (including
multiple bubbles and jets with a large degree of point-symmetry). These data,
difficult to explain under the existing paradigm, have led to the hypothesis
that fast collimated outflows with changing directionality are the primary
agent for the formation and shaping of PNe. We therefore propose to image a
statistical sample of such objects in order to test the new hypothesis. From
our images, we will determine the angular sizes of different nebular
components, which together with distances and expansion velocities, will allow
detailed tests of evolutionary models. Comparison of the morphologies of our
young PNe sample with more evolved PNe populations will set new constraints on
models for the production of jet-like outflows and nebular evolution.
================================================================================
Proposal Category: GO
Scientific Category: CLUSTERS, LENSING AND COSMOLOGY
ID: 8346
Title: Cosmological Parameters from Type Ia Supernovae at High
Redshift
PI: Saul Perlmutter
PI Institution: Lawrence Berkeley Laboratory

HST can directly measure the cosmological parameters, Omega, Lambda, and thus
the curvature, Omega_k, using Type Ia supernovae (SNe Ia) as calibrated
standard candles. Observations of SNe Ia spanning a large redshift range are
key to decoupling Omega and Lambda. For Cycle 7 and Cycle 7-NICMOS we proposed
a measurement of Omega and Lambda with uncertainty ~11\ at z~0.5 and six at
z~0.8 with WFPC and NICMOS; we have since embarked on this program and the
results have more than met our expectations. We now propose to extend this
successful project to study five additional SNe Ia between z~0.85 and z~1.2.
Measurement of these additional high redshift SNe will dramatically shrink the
major-axis of our current error ellipse in the Omega_M---Lambda plane, and
unambiguously determine whether the universe contains a significant vacuum
energy density as our current results strongly suggest. Results of these
proposed observations will further give the first real limits on whether the
universe is spatially flat. These data will test for evolution in the
properties of SNe Ia since it should be difficult for evolution to alter
corrected peak magnitudes with 15\ the redshift range 0 ================================================================================
Proposal Category: GO
Scientific Category: CLUSTERS, LENSING AND COSMOLOGY
ID: 8347
Title: The Gravitational Lens Candidate \PKS
PI: Arsen R. Hajian
PI Institution: United States Naval Observatory

High resolution radio interferometric observations of the radio target \PKS
show a bright, compact central source surrounded by several weaker discrete
clumps of emission. These data are difficult to reconcile with the standard
`core-jet' paradigm for active galaxies. Instead, modeling the radio image as
a gravitational lens appears to provide a much better interpretation of the
data. If true, \PKS represents the smallest gravitational lens yet discovered.
Furthermore, since it seems likely that the lensing object is a single galaxy,
the mass distribution of \PKS is simpler than many known lenses, and can be
more accurately modeled, thus potentially providing a valuable determination
of H_ o. The goal of this proposal is to confirm (or refute) the
gravitational lens model for \PKS through determination of the optical
continuum morphology and redshift(s). Since the total spatial extent of the
radio emission associated with \PKS is < 200 milliarcseconds, we propose to
use the high spatial resolution imaging capability of STIS imaging mode to
determine the optical emission structure of \PKSns, and then will followup
with spectroscopic observations using STIS in low dispersion spectroscopy mode
to measure the redshifts of the individual components of the putatively lensed
background source.
================================================================================

================================================================================
Proposal Category: AR
Scientific Category: GALAXY POPULATIONS AND INTERACTIONS
ID: 8348
Title: Ultraviolet Spectra of Galaxies with Active Star
Formation
PI: Claus Leitherer
PI Institution: Space Telescope Science Institute

Starburst galaxies are an energetically significant component of the local
universe. They are ideal laboratories to study massive stars, the interstellar
medium, and the physics of galaxy formation and evolution. Only the space-
ultraviolet regime contains the spectral signatures of stars accounting for
the bulk of the bolometric luminosity and their effects on the interstellar
medium. We propose to conduct an HST archival study of the extensive FOS and
GHRS database of starburst galaxies. The superior capabilities of HST provide
a significant improvement over previous work done with IUE data. We will study
the stellar content using line profiles of, e.g., C IV\ and [S II]v. The
kinematics of the interstellar medium will be probed with low-ionization lines
like \cii. The sample covers a wide range of morphological types (irregulars,
nuclear starbursts, blue compact dwarfs, etc.) and galaxy parameters
(metallicity, mass, rotational velocity, etc.). Our study will allow us to
gain insight into the star-formation history and the energetics of the ISM in
a statistically meaningful starburst sample and to place their properties into
a broad cosmogonical perspective.
================================================================================
Proposal Category: AR
Scientific Category: SOLAR SYSTEM
ID: 8349
Title: MAPPING TRITON
PI: Alan Stern
PI Institution: Southwest Research Institute

We propose to analyze an existing set of archival, high resolution UV and blue
HST/FOC images of Neptune's largest satellite, Triton, in order to obtain maps
at these useful wavelengths. Despite their quality, these Triton images have
never been analyzed in any detail, and no maps were ever made from them. The
resulting analyses and maps will be useful: (1) for determining the
distribution of volatiles and major photometric units on Triton, much as were
the images and maps of Pluto we obtained using the FOC in 1995; (2) to obtain
a baseline HST measurement for comparison over the next decade as Triton goes
through an expected (and indeed, perhaps already-starting) major, seasonal
change; and (3) having obtained the first-ever UV images of Triton, providing
spatial context for the rotationally-resolved Triton FOS mid-UV spectroscopy
that we obtained and analyzed previously (Stern et al. 1995). Our plan for
this AR project is to use the generalized mapping software that we developed
for the FOC Pluto project (Stern et al. 1997; Buie & Stern 1998), to
relatively quickly create similar data products and types of analyses for
Triton, so that this valuable archival dataset can be exploited. One of our
key goals is to search for evidence of changes in Triton's appearance due to
volatile transport between the 1989 Voyager encounter and these 1995 images.
================================================================================
Proposal Category: AR
Scientific Category: FIELD STELLAR POPULATIONS
ID: 8350
Title: A SEARCH FOR INTERGALACTIC STARS IN THE LOCAL GROUP
PI: Bart Wakker
PI Institution: University of Wisconsin-Madison

A profound change in our picture of the Local Group has been suggested by
Blitz et al.\ (1998), who argue that dex11 M(sun)\ of HI resides in a long
filament between the Milky Way and M 31, which they identify with the HI high-
velocity clouds (HVCs). Since many HVCs are known to contain heavy elements
(with a metallicity of >0.01 times solar), a critical test of the model is to
find the evolved stars within the population that produced these heavy
elements. We propose to search for these stars. Since the model of Blitz et
al.\ (1998) predicts HVC distances of >100 kpc, the stars will be faint
(V>24). However, we show that they can be found using starcounts on WFPC2
images, provided that the space density exceeds ~1/1000 that in the solar
neighborhood, Detecting intergalactic stars in the HI filament would allow a
determination of the distance to the HVCs, and establish the presence of a
completely new component of the Local Group. A negative result would allow
stringent limits to be set on the number of intergalactic stars and on models
for HVCs.
================================================================================
Proposal Category: AR
Scientific Category: SOLAR SYSTEM
ID: 8351
Title: Changes in Uranus' Atmosphere Since the Voyager Encounter
PI: Kathy Rages
PI Institution: NASA Ames Research Center (Space Physics Research
Institute)

We propose to combine all the available WFPC2 and NICMOS images of Uranus to
investigate the causes of Uranus' long-term temporal variability, including
several discrete clouds which apparently have lifetimes of several months. The
PI has already developed atmospheric scattering models to fit the Voyager
observations of Uranus' southern hemisphere (Rages Etal 1991, Rages and
Pollack 1994), and is now modifying them to reproduce the Cycle 6 WFPC2
observations of Hammel et al. We propose to enhance the vertical resolution
of the Cycle 6 models by inclusion of the Cycle 7 data of Tomasko et al., and
to model observations from previous cycles to investigate the timing of
possible changes in (1) the methane cloud's altitude, optical thickness, and
single scattering albedo; (2) aerosol absorption below the base of the methane
cloud; and (3) height of the putative H_2S cloud at ~3 bars. We will examine
northern latitudes up to ~30degrees N to check for possible hemispheric
asymmetries in the atmospheric structure. We will also study how the
structure of the discrete clouds differs from that of the surrounding
atmosphere. The work proposed here complements our previous Cycle 6, approved
Cycle 7 and requested Cycle 8 observations of Uranus by (1) extending the
wavelength range for modeling of our pre-1998 observations and (2) using data
from 1994 and 1995 to partially fill the 10-year gap since the Voyager
encounter.
================================================================================
Proposal Category: AR
Scientific Category: INTERSTELLAR AND INTERGALACTIC MATTER
ID: 8352
Title: Physical Conditions in Predominantly Atomic Interstellar
Clouds
PI: Steven Federman
PI Institution: University of Toledo

We propose to determine the physical conditions in interstellar sight lines
from archival GHRS spectra showing absorption from C I. The choice of sight
lines is based on the fact that observed molecular abundances are relatively
low. Analysis of the relative populations among fine structure levels in
neutral carbon will yield estimates for gas density and temperature. We will
incorporate published results on rotational excitation in H_2 to help
constrain the gas temperature. The high quality data on C I, examined with
our refined self-consistent set of oscillator strengths, will provide accurate
estimates of gas density. We will use the results from C I excitation to
further our studies in two areas. We will examine the extent of a separation
into low and moderately dense neutral material within a single cloud toward
stars in Scorpius and Ophiuchus and whether such stratification is a common
feature of interstellar clouds and therefore must be included in studies of
interstellar material on galactic scales. We will also obtain information on
the amount of CH associated with CH^+ synthesis as an aid to understanding
CH^+ formation in the low density portions of interstellar clouds, an unsolved
problem despite nearly fifty years of study.
================================================================================
Proposal Category: AR
Scientific Category: SOLAR SYSTEM
ID: 8353
Title: Constructing a 2-D Picture of Saturn's OH Cloud
PI: John Richardson
PI Institution: Massachusetts Institute of Technology

The discovery of OH changed our view of Saturn's magnetosphere from one where
plasma dominated the physics to one where neutrals are dominant. Four
different sets of Hubble/FOS observations map the OH emission; published
results from two data sets detected OH near the rings at 2 R_S and near the
icy moons at 4.5 R_S. These are line of sight observations which determine the
OH column density; more information is necessary to convert from column
density to number density. We propose to combine all four data sets to
reconstruct the OH density distribution. The data encompass 14 different lines
of sight at 4 different look angles. The full data set provides much stronger
constraints on both the radial and latitudinal distribution of OH than does
the published data. Building on past work, we will model the physics and
chemistry governing the neutral and plasma densities in Saturn's
magnetosphere, and constrain the neutral and plasma distributions observed by
HST, Voyager 1, and Voyager 2 to be consistent with our model results. The
result of this work will be a 2-D picture of the OH densities in the Saturn
magnetosphere, knowledge which is crucial for understanding neutral and plasma
sources. Our results will also provide a set of predictions and tools for
the Cassini mission experiments, as well as the context for linking data from
the Voyager missions, HST observations and the Cassini mission.
================================================================================
Proposal Category: AR
Scientific Category: CLUSTERS, LENSING AND COSMOLOGY
ID: 8354
Title: DIRECT Distances to M31 and M33 Using Detached Eclipsing
Binaries and Cepheids
PI: Dimitar Sasselov
PI Institution: Harvard-Center for Astrophysics

We propose to use the archival observations by the HST/WFPC2 in two important
galaxies in the cosmological distance ladder, M31 and M33, to identify the
variable stars we have already discovered from the ground. The new variables
come from our project, called DIRECT, aiming to obtain the distances to M31
and M33 using detached eclipsing binaries and Cepheids. Combining photometry
and spectroscopy for a selected subsample of binaries and Cepheids allows us
to derive direct distance of high accuracy, which rely on no intermediate
steps. We expect to identify 20--30\ HST/WFPC2 images, thus improving
significantly their photometry by quantifying systematic effects due to
crowding. This should aid in both the accuracy and precision of our direct
distance determination to M31 and M33, which are stepping stones for most of
our current efforts to understand the evolving universe at large scales. Thus
we expect to help in decreasing the HST Key Project's overall uncertainty in
deriving the Hubble constant, H_0, by a factor of 2 (or to about 5\
================================================================================
Proposal Category: AR
Scientific Category: AGN PHYSICS
ID: 8355
Title: Chemical Abundances and Geometry in QSO Broad Absorption
Line Regions
PI: Vesa Junkkarinen
PI Institution: University of California, San Diego

We propose to use archival HST UV spectra to study the chemical abundances in
QSO broad absorption line (BAL) regions while taking into account the geometry
of the emission/absorption regions and, in particular, partial covering of the
background sources by the absorber. Previous studies of BALQSO spectra point
to extreme metallicities, 50 to 100 times solar for some elements (Turnshek et
al. 1996) and a phosphorus to carbon ratio of around 65 times solar
(Junkkarinen et al. 1997). Other studies suggest that the abundances are 1 to
10 times solar (Korista et al. 1996). The extreme apparent metallicities may
result from ignoring, in the analysis, complex ionization and partial covering
effects (Hamann 1998). The combination of archival HST UV spectra with
existing optical spectra (including Keck HIRES spectra) will provide a better
test of both the ionization and partial covering effects. The UV spectra
include many lines and provide constraints on partial covering especially from
saturated lines that are not black. The high resolution Keck spectra of
isolated BALs provide extremely accurate absorption templates and give direct
measurements of partial covering in narrower components in the BAL outflow. An
analysis of BALQSO spectra that includes the background source geometry and
partial covering is now needed before the chemical abundances derived from
BALQSOs can be considered reliable.
================================================================================
Proposal Category: AR
Scientific Category: INTERSTELLAR AND INTERGALACTIC MATTER
ID: 8356
Title: Further Insights into Interstellar Dust Grains Using
Ultraviolet Polarimetry and Spectroscopy
PI: Michael J. Wolff
PI Institution: Space Science Institute

Understanding interstellar dust and its role in the universe is very
important. Virtually all observations of astrophysical objects and their
physical processes are affected by the presence of dust either within the
system being studied or along its line of sight. We propose a research program
that will appreciably enhance our knowledge of dust properties. The 11 Faint
Object Spectrograph datasets identified in the proposal represent a
significant fraction of all available ultraviolet interstellar polarimetry.
These data will be used to probe the connection of the grain size distribution
with sightline environment by employing such powerful techniques as the
maximum entropy method. We also propose an analysis of the Goddard High
Resolution Spectrograph data for HD 147933, one of only two objects with an
observed polarized 0.218 micron\ extinction feature. This aspect of our
program will derive gas phase abundances for several elements in an effort to
provide further insight into the unique nature of this sightline.
================================================================================
Proposal Category: AR
Scientific Category: DISTANT GALAXIES
ID: 8357
Title: Rest-frame Galaxy Morphology at Intermediate to High
Redshifts Using Archival NICMOS Images
PI: Ian Waddington
PI Institution: Arizona State University

\n We propose to investigate the observed infrared morphology of ~10^4 faint
galaxies at intermediate to high redshifts observed in ~160 shallow--deep
NICMOS H-band images, which sample the restframe optical. Artificial Neural
Networks that are well trained on lower redshift WFPC2 BVRI images will
provide reliable classifications for H 26.5--27 mag. We will then address the
following science goals: noindent (1) Determine the galaxy counts as as
function of accurately determined morphological type, providing strong
constraints on galaxy evolution models well beyond levels where these can be
measured spectroscopically from the ground; noindent (2) Measure the epoch
and type-dependent luminosity distribution N(z,mag,type) in the multicolor HDF
images, which will directly constrain the evolution of the different Hubble
types with cosmic time and trace the physical cause of this evolution at z~1--
3; noindent (3) Study the numerous compact objects at faint magnitudes,
their size distribution compared with that of nearby galaxies in the restframe
optical, and their role in galaxy formation; noindent (4) Provide stronger
constraints on cosmological parameters (e.g.\ the cosmological constant) from
the counts of well classified E/S0's, which cannot be done through the optical
counts since the uncertain restframe UV morphology affects the
classifications.
================================================================================
Proposal Category: AR
Scientific Category: STELLAR POPULATIONS IN CLUSTERS
ID: 8358
Title: A COMPLETE CENSUS OF HOT STARS IN GLOBULAR CLUSTERS
PI: Wayne Landsman
PI Institution: Raytheon STX

We propose to assemble a catalog of ultraviolet fluxes and colors for a
complete sample of about 4000 hot stars in twelve globular clusters. For
these clusters there are available both archival WFPC2 images of the cluster
cores, and wide-field (40') images obtained with the Ultraviolet Imaging
Telescope (UIT). The UIT data provide a complete census of the hot stars
but lack the color information which can only be provided in the cluster cores
by high resolution WFPC2 photometry. We will use this catalog of hot
stars to explore aspects of their astrophysics that are presently poorly
understood. Specifically, we will (1) test evolutionary tracks of hot
horizontal branch (HB) stars by comparing number counts of different phases
(2) search for radial gradients in the relative populations of extreme HB
(EHB) and blue HB stars, (3) search for statistically significant gaps in the
temperature distribution of hot HB stars (which can provide key clues to
physical processes taking place in red giant branch stars, such as mass loss
and deep mixing), and (4) assemble a complete catalog of ``exotic'' hot stars
in the twelve globular clusters.
================================================================================
Proposal Category: AR
Scientific Category: COOL STARS
ID: 8359
Title: The Spatial Location of the Flaring Regions on AB Doradus
PI: Frederick Walter
PI Institution: State University of New York

We request support to analyze 5 hours of GHRS spectra (600 individual spectra)
of the C IV lines of the active K dwarf AB Doradus. These data (program 5310)
were obtained immediately prior to our 14 hour GTO campaign (program 5181) on
this star on 14 November 1994. AB Dor is the prototypical young, active star.
Its atmosphere shows indications of domination by a large-scale global
magnetic field. We propose to analyze this data set in conjunction with our
GTO data and simultaneous photospheric doppler imaging, using tomographic
techniques to identify the locations of the flaring regions, and to correlate
them with the dark regions identified from optical spectroscopy and
photometry. These data bear on the question of whether the large dark regions
in active stars are solar-like magnetically-dominated spots, or are regions
more like solar polar coronal holes. This investigation may lead to a better
understanding of the nature of the stellar magnetic activity in the most
active stars.
================================================================================
Proposal Category: AR
Scientific Category: INTERSTELLAR AND INTERGALACTIC MATTER
ID: 8360
Title: How Opaque Are Spiral Galaxies?
PI: Ron J. Allen
PI Institution: Space Telescope Science Institute

Using HST Archival images in a previous modest AR program, we have developed a
new method to calibrate the effects of crowding and confusion from foreground
structure on the counts of background galaxies seen through a foreground
system. This new method, the Synthetic Field Method, permits us to establish
the area-averaged amount of extinction through the entire thickness of the
foreground galaxy. No assumptions about the spatial distribution of the
obscuring material in the foreground system or about its reddening law are
required. We now propose to exploit this method by applying it to deep
Archival images of all 17 nearby spiral galaxies obtained earlier with the
HST/WFPC2 in the Cepheid distance scale programs. Applying the method to this
large sample of spirals will permit us: (1) to decrease the fundamental
uncertainty in our results owing to field-to-field variations in the surface
number density of the background galaxies, and (2) to begin quantifying the
differences in extinction between arms and inter-arm regions, and between the
inner and outer parts of spiral galaxy disks. The results of this project will
provide the largest study to date of TOTAL extinction in spiral galaxies using
background illuminating objects.
================================================================================
Proposal Category: AR
Scientific Category: AGN HOSTS AND ENVIRONMENT
ID: 8361
Title: The Bulge Properties and Fueling Mechanisms of Nearby
AGNs
PI: Alex Filippenko
PI Institution: University of California at Berkeley

We recently completed an optical spectroscopic survey of nearby galaxies that
has shown that a substantial fraction of all galaxies, especially those of
early Hubble type, exhibit active galactic nuclei. Under the assumption that
these are powered by supermassive black holes (SMBHs), we conclude that SMBHs
appear to be common constituents of many, but not necessarily all, elliptical
and bulge-dominated galaxies. We wish to investigate why some galaxy bulges
seem more conducive than others to hosting SMBHs, or at least SMBHs with
associated activity. We propose to conduct a study of near-IR (NIR) archival
NICMOS images of galaxies from a representative sample of ``active'' and
``normal'' disk galaxies (S0--Sc) selected from our spectroscopic survey in
order to (1) quantify the bulge luminosity and (2) perform a comparative study
of the structural parameters of the bulges detected. The brightness profiles
of the central regions can be quantified much more reliably in the NIR than in
the optical because of the lower dust extinction and reduced sensitivity to
nuclear spiral arms and star-forming regions. In addition, we will use the
images to search for small-scale nuclear bars, either stellar or gaseous, as
well as nuclear star clusters, both of which have been suggested as possible
mechanisms for fueling the central engine.
================================================================================
Proposal Category: AR
Scientific Category: STELLAR POPULATIONS IN CLUSTERS
ID: 8362
Title: The Cluster Formation Rate in Nearby Galaxies
PI: Paul Hodge
PI Institution: University of Washington

We propose to study the formation rate of star clusters in galaxies in order
to understand better the large dispersion in the open cluster specific
frequencies found for different galaxies. Our initial emphasis will be on
M31. As the nearest giant spiral galaxy, M31 has been the subject of many
studies, including many HST programs. The open clusters of this galaxy,
however, have been relatively neglected. Although some 400 candidate open
clusters of various ages were identified from the ground nearly 20 years ago,
they have not been systematically studied since. This is largely the result
of the fact that ground-based images do not easily resolve the clusters,
making it difficult or impossible to determine their properties
quantitatively. With HST it is possible to do useful quantitative studies of
open clusters and to realize their usefulness as indicators of star formation
rates as a function of time as well as their importance as probes of modes of
star formation in different galactic environments.
================================================================================
Proposal Category: AR
Scientific Category: SOLAR SYSTEM
ID: 8363
Title: An Archival Study of the Quiescent and Disturbed
Atmosphere of Saturn
PI: Nancy Chanover
PI Institution: New Mexico State University

We propose to analyze five imaging data sets of Saturn taken between 1990 and
1995 in an effort to compare the quiescent and disturbed atmosphere of Saturn.
During this time interval, there were two large convective disturbances that
appeared near Saturn's equatorial region. The data taken during the 1995 ring
-plane crossings of Saturn provide a uniquely symmetric view of the northern
and southern hemispheres in a quiescent state, relatively unobscured by
Saturn's ring system. We will first model the vertical structure of the
undisturbed atmosphere at latitudes known to exhibit little or no temporal
variation using a multiple scattering adding/doubling radiative transfer code.
We will use this general atmospheric model to predict what the same latitudes
would look like in the 1990 WF/PC Saturn storm data. This will enable us to
characterize the effect of deconvolution on the photometric integrity of the
data set. Once we determine that the photometry of the 1990 Saturn storm data
has been retained, we will use the doubling code to place limits on the
vertical extent of the 1990 and 1994 storms. Finally, we will utilize a
buoyancy analysis of the two systems to characterize the energy deposited into
Saturn's atmosphere by these convective disturbances. This will yield new
information about the Saturnian atmosphere that will prove valuable for the
interpretation of the anticipated Cassini data sets.
================================================================================
Proposal Category: AR
Scientific Category: COOL STARS
ID: 8364
Title: Search for Brown Dwarfs around Nearby Stars
PI: S. R. Kulkarni
PI Institution: California Institute of Technology

The recent discoveries of substellar objects, including exoplanets and brown
dwarfs, is rapidly revising our earlier pessimistic view of their abundance.
The bizarre spectrum of the cool brown dwarf Gliese 229B, with strong features
due to water and methane, has been the principal guide to the design of
searches for more such objects. However, to date Gliese 229B remains the only
cool brown dwarf known. We propose to use the NICMOS snapshot survey of stars
within 10 pc of the sun to conduct an unbiased search for companions of these
stars, based solely on their proper motions. The principal goal of the NICMOS
survey was to find objects similar to the brown dwarf Gliese 229B by using
differential imaging with filters which lie in and out of characteristic
absorption bands. The survey, however, is limited because it can not
establish with certainty that any object fitting the description above is an
actual companion of the star nor could it find companions that are different
from Gliese 229B. We have an extensive database of optical and near infrared
images of the 1'\ fields of view centered on these stars. These images were
taken repeatedly at multiple epochs over the past four years. With this data
we can easily determine whether any of the point sources in the NICMOS images
are common proper motion companions. We will publish all common proper motion
companions found.
================================================================================
Proposal Category: AR
Scientific Category: STELLAR EJECTA
ID: 8365
Title: Measuring Eta Car's Giant Eruption by Modeling Dust
Scattering and Emission in the Homunculus
PI: Barbara Whitney
PI Institution: Prism Computational Sciences, Inc.

The goal of this proposal is to determine better estimates of some fundamental
quantities of the Eta Car Homunculus through modeling of HST imagery. These
quantities are: total mass of the emitting gas and dust, and the latitudinal
distribution of dust. The total mass is fundamental because it says something
about the kinetic energy of the eruption which, based on the current
estimates, now sits right up there with the bolometric luminosity of the star.
The latitudinal distribution says something about the nature of the initial
mass loss mechanism that caused the outburst. To get at these quantities, we
will need to model the image morphology confirming the shape of the homunculus
and inclination, model the dust scattering properties, and estimate the dust-
to-gas ratio. The wavelength coverage provided by the WFPC2 camera will nicely
constrain dust models as the large difference in opacities will sample
different optical depths. The narrow-band images will be used in conjunction
with imaging models to estimate the gas-to-dust ratio. We will use accurate 3-
D radiation transfer codes and hydrodynamic codes as our modeling tools.
================================================================================
Proposal Category: AR
Scientific Category: SOLAR SYSTEM
ID: 8366
Title: A Critical Extension to Martian Ozone Abundances Using
WFPC2
PI: Barbara A. Whitney
PI Institution: Prism Computational Sciences, Inc.

We propose to use archival WFPC2 data to determine the atmospheric ozone
abundances on Mars for a period not well studied by previous efforts. This
quantity is a fundamental diagnostic of that planet's atmospheric processes.
The multi-year coverage of the WFPC2 data (1995-7) provides information about
the latitudinal, seasonal, and interannual variations of Martian ozone column
densities. We will focus our efforts on the period from late spring through
the end of summer (in the northern hemisphere), with special attention given
to low-to-mid latitude regions where coverage is very incomplete. We will
model the ozone absorption in the Hartley Band taking into account Rayleigh
scattering, dust, and cloud opacities. Our analyses will involve F255W, whose
throughput curves are ideal for measurements of the Hartley Band, F336W, and
F410M. We maximize sensitivity to small amounts of ozone by examining regions
with large atmospheric pathlengths (i.e., near the limb). Artifacts
associated with image restoration are avoided by, instead, convolving the
models with the relevant point spread function. Our approach, in combination
with the unique nature of the requested dataset, will allow for the most
accurate and extensive ozone abundances to date for the seasons sampled. The
Mars Global Surveyor does NOT have capability to provide such information.
================================================================================
Proposal Category: AR
Scientific Category: YOUNG STARS AND CIRCUMSTELLAR MATERIAL
ID: 8367
Title: Testing Protostellar Collapse and Outflow Models
PI: Barbara Whitney
PI Institution: Prism Computational Sciences, Inc.

This proposal is to model high-spatial resolution WFPC2 and NICMOS imagery of
the Taurus protostars. By applying 3-D radiation transfer codes that include
accurate treatment of dust scattering and clumping effects, and 2-D
hydrodynamic codes to the best available high-spatial resolution imagery of
these sources, we will learn more about the following scientific issues: 1)
if the envelope density really matches the rotationally-flattened infall
solution, or is it in fact more complicated than that? We will include other
infall solutions such as magnetic collapse and collapse from clouds with
initial motion. 2) how the outflows shape the cavities and disperse the
envelope; we will use hydrodynamic simulations to test if our presumed
geometries are physically plausible and produce images that match the
observations. 3) how prevalent are multipolar cavities, and 4) the dust
properties in protostars.
================================================================================
Proposal Category: AR
Scientific Category: DISTANT GALAXIES
ID: 8368
Title: Constraints on the Evolution of Dwarf Elliptical Galaxies
from Deep HST images
PI: Henry C. Ferguson
PI Institution: Space Telescope Science Institute

The aim of this program is to test models for the late (z <~ 1) formation of
dwarf elliptical galaxies. Such late formation arises as a fairly natural
consequence of proposed solutions to the ``overcooling'' problem in theories
of hierarchical structure formation. Correlations of dwarf galaxy numbers and
ages with the density of the environment are also predicted. The data exist
now to test such hypotheses. We will construct models of dE galaxy evolution -
- constrained to be consistent with color and luminosity distributions in
local samples -- and compare them directly to deep HST images of clusters and
blank fields. A range of luminosity function shapes and normalizations will be
tested to identify those that are consistent or inconsistent with the number
counts of dE-like galaxies in blank fields such as the HDF, and in the fields
of high-redshift clusters. The models will take into account
spectrophotometric evolution, density evolution, the possible morphological
transformation of irregular galaxies to dE's, and selection effects.
================================================================================
Proposal Category: AR
Scientific Category: BINARY STARS
ID: 8369
Title: Evolution of the Symbiotic Nova AG Pegasi
PI: Scott J. Kenyon
PI Institution: Smithsonian Astrophysical Observatory

We propose to study high signal-to-noise FOS and GHRS observations of the
symbiotic nova AG Pegasi. We plan to analyze the ultraviolet spectra together
with contemporaneous low resolution optical spectrophotometry of similarly
high quality. These data will allow us to examine the line and continuum
fluxes and radial velocities at several orbital phases for species with
ionization potentials ranging from ~ 10 eV up to ~ 100 eV. We expect three
main results from this program. (i) Orbital modulation of the emission line
fluxes will yield a better understanding of the geometry of the ionized wind
of the red giant primary star. This result will test our predictions that low
ionization lines form near the red giant photosphere and that higher
ionization species lie close to the accreting white dwarf companion. (ii)
Emission line radial velocities will help to constrain the wind geometry and
may place limits on the mass of the white dwarf. (iii) The continuum and
emission line fluxes will test predictions of our non-LTE photoionization
code. We have derived order-of-magnitude estimates for the mass loss rate in
the red giant wind and placed some limits on the velocity law in this wind
from archival IUE spectra. The HST data will yield better constraints on
these wind parameters and begin to test hydrodynamical models for wind
accretion in detached binaries.
================================================================================
Proposal Category: AR
Scientific Category: BINARY STARS
ID: 8370
Title: Duplicity and Variability in HST Guide Stars - An FGS
Serendipitous Survey
PI: Glenn Schneider
PI Institution: University of Arizona

With the successful completion of AR/5811 we have demonstrated the efficacy of
extracting fundamental astrometric properties of stellar systems from HST
guiding data. The HST Fine Guidance Sensors (FGS) are capable of revealing
duplicity in faint, close binary systems and measuring their position angles
and component separations with a precision which far exceeds that which is
possible using other techniques. Intensity data which are produced by the FGS
PMTs while in fine lock provide high precision relative photometry on rapid
time scales. As proposed in AR/5811 we have built a data reduction and
analysis pipeline to exploit these capabilities in a serendipitous fashion
using HST guiding data. We have recently publish a new duplicity catalog from
a search of 4882 HST guide stars observed in 13,979 acquisitions spanning 22
months giving separations, position angles, and relative brightnesses of the
individual stellar components. Our pipeline also extracts FGS photometric data
in a form which permits examining light curves and power spectra for
astroseismological surveys of these stars, while looking for and
characterizing variations due to other intrinsic mechanisms. We now propose to
take full advantage of the ground-work which has been established by our pilot
program by continuing this survey for the large number of guide stars still to
be examined, and which will be observed in Cycle 8.
================================================================================
Proposal Category: AR
Scientific Category: GALAXY POPULATIONS AND INTERACTIONS
ID: 8371
Title: Near-UV Spectra of Andromeda Globular Clusters Compared
to Spectral Calculations
PI: Ruth Peterson
PI Institution: Astrophysical Advances

The near-ultraviolet spectrum of an old stellar population offers the best
hope for determining its age and metallicity, since it is dominated by stars
near the main-sequence turnoff. We have begun the first step towards this goal
by calculating spectra from first principles from 2400Angstrom\ to
3200Angstrom\ for late F and early G stars near the main sequence. The
calculations span metallicities 0.1 to 5* solar, and agree well at the low end
with stellar IUE and HST spectra. Here we propose to compare archival near-UV
spectra of four globular clusters in M31 against theoretical composite spectra
to be derived from the grid. Calculated spectra for stars of various
temperature and gravity will be weighted and coadded at each of several levels
of overall metallicity and relative light-element abundance. We will check the
validity of each satisfactory near-UV match against the available color-
magnitude diagram and optical spectroscopy for each cluster. The results
should show, at each cluster metallicity, how accurately age and metallicity
may be derived from near-UV spectra alone and what observational requirements
on wavelength coverage, S/N, and resolution are entailed for extragalactic
objects which cannot be spatially resolved or optically observed.
================================================================================
Proposal Category: AR
Scientific Category: FIELD STELLAR POPULATIONS
ID: 8372
Title: Massive emission-line stars in nearby galaxies
PI: Rene Walterbos
PI Institution: New Mexico State University

The HST archive contains numerous exposures in HAlpha and continuum light of
nearby (< 10 Mpc) galaxies. We propose to analyze these archival images to
create a database of massive stars with high mass-loss rates for galaxies of
different Hubble types. The catalog is expected to include candidate Luminous
Blue Variables (cLBV), Be stars and possibly some Wolf-Rayet stars. The HST
data are unique for several reasons: 1) the high spatial resolution and
inclusion of continuum exposures allows us to extend successful ground-based
searches for stars with high mass loss rates in the MCs, M31 and M33 out to
ten times larger distances. Their HAlpha luminosities and continuum emission
provide estimates of the mass loss rates; 2) for galaxies out to a few Mpc,
the high resolution allows a search for resolved nebulae possibly indicating
eruptive mass loss; such nebulae are known to exist around LBVs in the Galaxy
and the LMC; and 3) data are available for different galaxy types with a range
of metallicities which will ultimately help in testing the ``Conti scenario''
for massive stellar evolution. The number of cLBVs and other extreme mass-loss
stars we expect to find, ranges from a few in the closest galaxies to as much
as 50 in M101. Finding these objects is an important first step in shedding
light on the poorly understood post-main sequence evolution of massive stars.
================================================================================
Proposal Category: AR
Scientific Category: GALAXY STRUCTURE AND DYNAMICS
ID: 8373
Title: The Evolution of the Mass--to--Light Ratio of Spiral
Galaxies
PI: Riccardo Giovanelli
PI Institution: Cornell University

We propose to study the M/L ratio of spiral galaxies up to a redshift of 1/3,
using the Tully--Fisher relation. That goal will be achieved by access to HST
archival data, which will provide a target list of galaxies to be observed
with the upgraded Arecibo telescope at 21 cm. HST images are of paramount
importance in the project, as for redshifts higher than 0.1 it is impossible
to obtain sufficiently accurate estimates of galaxy morphology and disk
inclination with ground--based images. We have cross--referenced the HST data
base with catalogs of galaxy redshifts and conclude that a sample of nearly
100 target galaxies suitable for this study can be obtained using the HST
archives.
================================================================================
Proposal Category: AR
Scientific Category: GALAXY STRUCTURE AND DYNAMICS
ID: 8374
Title: The Morphology of Dust Lanes in Barred Spirals
PI: Beverly Smith
PI Institution: University of Colorado

We propose to use the HST archives to investigate gas inflow along bars in
spiral galaxies, by studying in detail the structure of the dust lanes along
these bars. In nearby galaxies, these dust lanes are typically about 1'' wide
(50 pc at a distance of 10 Mpc) and so are unresolved or nearly unresolved on
groundbased images. With the unprecedented resolution of HST, however, these
features are well-resolved, providing the opportunity to study their structure
in detail. These dust lanes trace the inflowing gas, which is difficult to
detect directly along bars, and so provide information about clumping, shocks,
and cloud formation in the inflowing gas. The HST archives contain a large
number of WFPC2 images of nearby spiral galaxies. With these data, we will be
able to determine if these lanes are continuous or clumpy and if they are
separated into multiple streams. With the large sample of data available, we
will be able to determine if the structure varies from galaxy to galaxy and if
there are trends (i.e., are the lanes clumpier, weaker, and/or wider in weaker
bars? In galaxies without strong circumnuclear star formation?). These data
will provide a valuable test of theoretical models of gas inflow along bars,
addressing questions about the importance of self-gravity, viscosity, and
shocks in driving gas inflow.
================================================================================
Proposal Category: AR
Scientific Category: AGN HOSTS AND ENVIRONMENT
ID: 8375
Title: ACCRETION DISKS AND DUST DISKS IN ACTIVE ELLIPTICAL
GALAXIES
PI: Anne Kinney
PI Institution: Space Telescope Science Institute

We aim here to study the relation between optical/radio nuclear activity and
resolvable dust/gas disks in active ellipticals. We will do this by analyzing
a complete, unbiased sample of 112 galaxies chosen on a nearly isotropic
property, the diffuse radio flux at 178 MHz. In order to understand the
significance of the detected dust in the active ellipticals, we will also
analyze a control sample of 135 normal ellipticals matched in starlight
luminosity and central surface brightness for comparison. The inner dust
structures which probe the effects described here appear on very small scales
and generally cannot be observed from the ground. The relative position angle
between the radio axis and the dust disk serves as a powerful diagnostic; the
orientation of the outer dust disk has the potential to reveal the history of
a triggering merger, while the orientation of the innermost dust disk reveals
the structure of the accretion disk on ~ 10-100 pc scale. Finally, the radio
jet indicates the innermost axis which is generated on scales of ~ 100 R_G or
less. With a sample that includes FRI's, FRII's (with luminous active nuclei
and ``optically dull"), and normal elliptical galaxies, we can test
predictions for the causes of activity, current ideas about the dynamics of
the gas/dust involved in mergers, and probe the physics of the resulting
accretion disks.
================================================================================
Proposal Category: AR
Scientific Category: COOL STARSS
ID: 8376
Title: A Semi-Empirical Model of the Structured Wind of 32 Cygni
PI: Philip Bennett
PI Institution: University of Colorado

I propose to construct a semi-empirical wind model of the supergiant primary
of the eclipsing binary 32 Cygni (K5 Iab + B6 V), using archival HST/GHRS
observations obtained at 6 epochs around the December 1996 eclipse. From these
observations, I will empirically determine the hydrogen column density
structure along each line of sight to the early-type secondary star using the
Tau--v method. I will use codes developed for the analysis of HST/GHRS
observations of the similar binary Zeta Aur. Successful Tau--v inversion of
the UV absorption line profiles requires high spectral resolution and high
S/N, limiting the useful data to those from HST/GHRS. Recent HST/GHRS
observations of Zeta Aur in Cycles 2 & 5, and of 32 Cyg in Cycle 6, have shown
the primary's wind has discrete structure along some lines of sight. However,
global flux diagnostics such as UV emission line profiles and radio continuum
fluxes, show that the globally-averaged wind is only slightly variable in
time, implying most of the observed variability in the absorption lines is on
small scales. Semi-empirical mean models of these winds are useful
================================================================================
Proposal Category: AR
Scientific Category: SOLAR SYSTEM
ID: 8377
Title: Multispectral Investigation of Jovian Cloud Structure
PI: Lawrence Sromovsky
PI Institution: University of Wisconsin-Madison

We propose to use archived HST images of Jupiter, made before and after the
December 1995 Galileo Probe in-situ observations, to investigate cloud
structure in and adjacent to the probe entry point and in similar regions at
other locations. Prior analyses of Jovian cloud structure, having limited
constraints to apply to an underdetermined problem, made assumptions such as
semi-infinite clouds, equality of single scattering albedos for upper and
lower clouds, uniform phase functions for all wavelengths, and specific cloud
base locations. We propose to use new constraints on cloud properties and
abundance of condensible species provided by the Galileo Nephelometer, Net
Flux Radiometer, and Mass Spectrometer, to reduce the solution space for
interpreting remote observations. The primary HST inputs into the proposed
analysis will be the wavelength-dependent albedo and limb darkening
characteristics of hot spot regions and their surroundings, using WFPC2 and
NICMOS imaging from UV to 2.3 microns, with varying Rayleigh scattering and
gas absorption as probes of vertical structure, and continuum wavelengths as a
probe of particle properties. We will also use several Galileo orbiter images
to help constrain heterogeneous and vertical structure using the intermediate
methane absorption band at 7270Angstrom .
================================================================================
Proposal Category: AR
Scientific Category: CLUSTERS, LENSING AND COSMOLOGY
ID: 8378
Title: The Globular Cluster Luminosity Function as a Distance
Indicator
PI: Bradley Whitmore
PI Institution: Space Telescope Science Institute

We propose to use existing WFPC2 images of nearby elliptical and S0 galaxies
to test the reliability of the Globular Cluster Luminosity Function (GCLF) for
the purpose of making distance estimates. The `standard candle' of this
method is the turnover point of the GCLF at M_V^0 ~eq -7.3 mag. The empirical
evidence currently available, mostly from the Virgo and Fornax ellipticals, is
that the internal precision of the GCLF turnover is +/-0.15 mag per galaxy,
making the method competitive with even the best distance indicators. However,
there is tentative evidence that effects such as dynamical evolution and
differences in metallicity (among other second-order parameters) may slightly
alter the turnover point. This provides the opportunity to reduce the already-
small internal scatter of the method still further, and the possibility of
better understanding the origin and evolution of globular clusters. We
propose to pursue these goals by determining the GCLF for a sample of ~eq 80
galaxies from the archives, and searching for differences in the turnover as a
function of cluster color, position within the galaxies, and environment of
the galaxy. Our longer term goal is to use this data set to support a
proposal using the Advanced Camera for Surveys (ACS) to measure H_0 to within
an internal precision of 5\ (external) precision of 7\
================================================================================
Proposal Category: AR
Scientific Category: DISTANT GALAXIES
ID: 8379
Title: Search for Emission Line Galaxies in the Near Infrared
Using the NICMOS Grism Data
PI: Lin Yan
PI Institution: Carnegie Observatories

NICMOS has produced a wealth of grism spectroscopic data in the 0.8Mu to 1.9Mu
wavelength range. To date roughly 650 primary and parallel orbits of grism
data have been obtained at high and intermediate galactic latitudes. We
propose an archival research program using this database to search for high
redshift emission line objects, to measure the global star formation history
at various epochs and to study the evolution of field galaxies. We have
analyzed nearly all of the G141 grism (Lambda ~ 1.1Mu - 1.9Mu) exposures taken
to date by the public pure-parallel program. This dataset reaches 3Sigma flux
limits of (1 - 0.2)* 10^-16 erg/s/cm^2 for integration times of 2,000 to
21,000 seconds. The NICMOS data have lower flux limits than all of the
previous near-IR emission-line surveys, including those with the Keck
telescopes. We have developed expertise in reducing the NICMOS grism data and
have identified 33 emission-line galaxies in 83 square arc-minutes of G141
data. In this proposed program, we will: 1) reduce the entire NICMOS grism GO
and GTO data sets; 2) search for emission-line objects over ~ 170 square
arcmin, roughly doubling our present sample; (3) derive the global star
formation history to z ~2; (4) measure the spectral continuum for bright
galaxies which don't have emission lines in our observed wavelength range; and
(5) make all of the reduced grism data available to the public.
================================================================================
Proposal Category: AR
Scientific Category: DISTANT GALAXIES
ID: 8380
Title: Star Formation in Galaxies at 0 PI: Jonathan P. Gardner
PI Institution: NASA - Goddard Space Flight Center

The installation of STIS on HST has allowed two-dimensional optical and
ultraviolet slitless spectroscopy of faint objects from space for the first
time. The STIS Parallel Survey (SPS) routinely obtains broad band images and
slitless spectra of random fields in parallel with HST observations using
other instruments. The SPS is designed to study a wide variety of
astrophysical phenomena, including the rate of star formation in galaxies and
detection of emission-line galaxies at intermediate to high redshift. We have
presented the first results of the SPS in Gardner et al (1998), which
demonstrated the capability of STIS slitless spectroscopy to detect and
identify emission-line galaxies. The redshift range of 0.0 particular cosmological interest, as it approaches the peak of star formation
and an epoch of significant galaxy and cluster evolution. The SPS provides a
unique view into this important epoch through detection of emission line
objects at 0.0 propose to reduce and co-add the direct and spectral images of the SPS and
make them and a catalog of detected objects available to the astronomical
community through the World Wide Web. We propose to identify the emission line
galaxies, and use their numbers, redshifts and magnitudes to determine the
star formation rate of the universe at this important epoch.
================================================================================
Proposal Category: AR
Scientific Category: DISTANT GALAXIES
ID: 8381
Title: Quantitative NICMOS Structural Parameters of Galaxies in
the Hubble Deep Field - North
PI: David C. Koo
PI Institution: Lick Observatory, University of California

The Hubble Deep Field - North (HDF-N) is an unquestionably unique laboratory
for studying the formation and evolution of distant galaxies. We propose to
analyze all the galaxies in the complete NICMOS map of the HDF-N with a PSF-
convolved ``bulge/disk'' surface brightness model. These quantitative
structural measurements in the near-infrared will be combined with WFPC2
optical measurements to answer four basic questions: (1) Are the underlying
structures of distant galaxies significantly altered (or even hidden) by dust
and star formation to which optical images are particularly sensitive? (2) How
do dynamical masses seen in recent Keck measurements of internal kinematics of
distant galaxies compare with total masses of old stars in the near-IR? (3) Is
the paucity of elliptical galaxies seen in the HDF-N due to dust or late
hierarchical galaxy formation? (4) What are the spatially resolved age and
star formation histories of HDF-N galaxies? The proposed archival work will
be an essential part of the structural and kinematical HDF-N dataset we
currently have in hand, and the results will guide our future Keck efforts.
================================================================================
Proposal Category: AR
Scientific Category: AGN HOSTS AND ENVIRONMENT
ID: 8382
Title: HST Observations of MilliJansky Radio Sources from the
FIRST Survey
PI: Richard L. White
PI Institution: Space Telescope Science Institute

The VLA FIRST survey is planned to cover 10,000 square degrees of the North
and South Galactic Caps at 1.4 GHz to a peak flux density limit of 1 mJy with
an angular resolution of 5"\ and source positions better than 1"\ down to the
catalog detection limit. Data taken through the summer of 1998 cover ~6000
square degrees of sky. The source catalog from this area contains about
550,000 objects. The median optical brightness of mJy radio galaxies is V ~
23.5. The number of magnitude 23.5 galaxies per square degree is large (~
2.5*10^4\ hboxdeg^-2), so that our positions of <1" accuracy are required to
identify the optical counterparts with confidence. The FIRST survey is the
first wide area radio survey with positions accurate enough to identify and
study the faint optical counterparts for the majority of the sources. Of
course, these galaxies are not only faint; they are also of small angular size
and usually have point-like, active nuclei. Only HST has the angular
resolution required to study the morphology and evolution of these objects. We
propose to study the optical, ultraviolet, and infrared characteristics of a
large sample of faint radio galaxies by analyzing all the publically available
WFPC2, NICMOS, and STIS images in the HST Data Archive that contain cataloged
FIRST sources.
================================================================================
Proposal Category: AR
Scientific Category: AGN PHYSICS
ID: 8383
Title: Survey of Extended OIIILambda5007Angstrom\ Emission in
Seyfert Galaxies
PI: Anne Kinney
PI Institution: Space Telescope Science Institute

We propose to analyze archival OIIILambda5007Angstrom\ images of 14 Seyfert
galaxies. These data will be used to complement a snapshot survey proposal to
obtain narrow band OIIILambda5007Angstrom\ images for a well defined sample of
190 Seyfert galaxies (52 Seyfert 1s and 138 Seyfert 2s), selected from a
mostly isotropic property, the 60Mum luminosity. These data will be used: 1)
to study the frequency of conically shaped Narrow Line Regions (NLR) in
Seyfert galaxies, which are usually unresolved from ground-based observations
and to compare the size and shape of the NLR of Seyfert 1s and Seyfert 2s; 2)
to measure the orientation of the accretion disk relative to the host galaxy
disk, so as to establish whether indeed the accretion disk axis avoids close
alignment with the host galaxy disk axis as indicated in early studies and; 3)
to compare the spatial relation between radio and NLR emission, using OIII
images and radio maps of comparable resolution. We aim to provide a critical
test of the applicability and limitations of the Unified Schemes that
currently are the framework for understanding Seyfert galaxies and their
luminous counterparts, AGN.
================================================================================
Proposal Category: AR
Scientific Category: DISTANT GALAXIES
ID: 8384
Title: The Morphology of Faint WFPC2 Galaxies
PI: Kavan Ratnatunga
PI Institution: Carnegie Mellon University

Field galaxies imaged with WFPC2 have formed a unique and invaluable database.
Galaxies parameterized by morphology, magnitude, color, half-light radius,
axis-ratio, orientation and location comprise a database used for long term
statistical studies in cosmology. We propose to generate a catalog from all
suitable WFPC2 exposures taken with broadband filters and split for cosmic-
rays, nearly doubling the number of the better quality WFPC2 fields which are
currently available in the Medium Deep Survey (MDS) database. We will add
homogeneously the primary archival material from Cycles 4-7 (including HDF
south) and future primary and parallel exposures from Cycles 7 and 8. The
resulting database with quantitative parameter estimates will be statistically
analyzed to model the distribution and evolution of galaxy morphology and weak
gravitational lensing. The semi-automated MDS software for WFPC2 data is
currently the only pipeline which can handle this large data reduction task.
The catalog will be made available via the existing searchable MDS database on
the web. The enlarged catalog, surveying a statistically significant area
well distributed in the sky to average over expected random fluctuations in
narrow fields of view, will also fill the intermediate magnitudes between the
brighter Sloan Survey and the fainter HDF fields.
================================================================================
Proposal Category: AR
Scientific Category: DISTANT GALAXIES
ID: 8385
Title: The Five Deep Fields: Lyman Break Galaxies from Multi--
Color WFPC2 Images
PI: Mark Dickinson
PI Institution: Space Telescope Science Institute

The Hubble Deep Field provided a high--quality, public data set for
identifying galaxies at 2 < z < 4.5 using the ``Lyman break'' technique.
These data have been used to derive the global evolution of cosmic star
formation and to study the morphological and photometric properties of star
forming, high redshift galaxies. HST--selected Lyman break galaxies probe
lower luminosities than do ground--based samples, defining the faint end of
the high redshift luminosity function and enabling studies of clustering
segregation, an important test of biased galaxy formation theory. However,
with only a single survey field (the HDF), small number and small volume
statistics fundamentally limit many conclusions which can be drawn about this
population. Here we propose to carry out a uniform analysis of Lyman break
galaxies from five separate fields: the HDF--South and North, plus three
additional public data sets with deep WFPC2 imaging through three or more HDF
filters. We will reduce the new fields, distribute the images to the
community, define a uniform catalog of HST--selected Lyman break objects, and
use them to study (1) the luminosity function, (2) global UV luminosity
density, (3) clustering segregation, and (4) morphological ``families'' of
Lyman break galaxies. Such data will greatly enhance the statistical
robustness of previous conclusions, and test whether or not the original HDF
represents a fair sample of the Universe.
================================================================================
Proposal Category: AR
Scientific Category: GALAXY STRUCTURE AND DYNAMICS
ID: 8386
Title: The Nature of Dusty Nuclear Disks in Early Type Galaxies
PI: Holland Ford
PI Institution: The Johns Hopkins University

We propose to use WFPC2 images extracted from the HST archive to construct a
volume limited (v <= 3000 km/s) sample of E and E/S0 galaxies with 3Sigma or
greater IRAS detections at 100 micron to search for small (r ~ 1'') dusty
nuclear disks. Preliminary analysis of WFPC2 archive images shows that more
than half of the sample will have small nuclear disks and disk-like
structures. The galaxies with disks will provide an efficient means to answer
outstanding questions about the relationship between massive black holes and
their host galaxies. Subsequent HST/STIS and ground-based infrared
spectroscopy of the disks will be used measure the central potentials and mass
distributions. We will use the archive images to: o study the role played by
galaxy environment in determining the frequency of dusty disks; o gain
insights into the origin of the dust and the role of the stellar potential and
the galaxy merging history in shaping the disks; o investigate the connection
between the presence and morphology of the disks and the frequency and
intensity of the nuclear activity.
================================================================================
Proposal Category: AR
Scientific Category: STELLAR EJECTA
ID: 8387
Title: The FeII Spectra of Eta Carinae: Implications for Atomic
and Plasma Astrophysics
PI: Dmitri Verner
PI Institution: University of Kentucky

The FeII emission spectrum is a ubiquitous one, appearing in such objects as
stars, protostellar disks, HII regions, novae, supernova remnants, active
galaxies and quasars. Its interpretation is painfully difficult because of
the great complexity of the Fe^+ energy level structure. We have embarked on a
long term program to fully simulate the physical conditions within FeII-
emitting gas and then predict the resulting spectrum. The first steps, the
generation of the initial data base and its incorporation into the radiative-
collisional code Cloudy, are complete. Now we request archive HST observations
of the massive star Eta Carinae. Although Eta Carinae is one of the most
studied stellar objects, its spectrum of FeII emission lines is still poorly
understood. We plan to attack the FeII spectrum from two directions: (1) by
detailed self-consistent quantitative modelling of all excitation mechanisms
of the FeII atom interacting with its environment, (2) and by validating
existing and calculating new atomic data for FeII. The rich FeII spectra of
Eta Carinae will allow us to check the reliability and completeness of the
atomic data and processes considered, to investigate the sensitivity of
emission lines to temperature and density variations, to assess the importance
of blending, and hence to quantify what FeII emission tells us about iron
abundances in other objects.
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Proposal Category: GO
Scientific Category: FIELD STELLAR POPULATIONS
ID: 8389
Title: Illuminating the Galactic Dark Matter
PI: Rodrigo Ibata
PI Institution: European Southern Observatory

We propose to re-image the HDF in F606W in order to confirm and better
determine the proper motions of four MACHO candidates discovered from the
comparison of the original December 1995 HDF frames with WFPC2 F814W frames
exposed in December 1997. Four very faint, blue, isolated and unresolved
objects are found to have substantial proper motion, 52 +/- 10 \mas, 102 +/-
14 \mas, 46 +/- 10 \mas and 69 +/- 11 \mas over the two year baseline.
Galactic structure models predict a complete absence of normal stars in the
color-magnitude range in which these objects are observed. However, these
observations are consistent with recently derived models of old hydrogen
atmosphere white dwarfs, whose color, contrary to previous expectations,
has been shown to be blue. If so, the stars we have detected have ages in
the range 10 \Gyr --> 14 \Gyr. With a correction for the incompleteness of
the sample, the number density of such objects is ~ 0.02 pc^-3, or ~ 0.01
msun pc^-3, assuming for their masses a value typical of white dwarfs.
Within the uncertainties arising from the small size of the sample, this
mass density is sufficient to account for the entire missing Galactic
dynamical mass. The present observations aim to confirm this potentially
very important finding.
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