Документ взят из кэша поисковой машины. Адрес оригинального документа : http://www.stsci.edu/hst/proposing/docs/exp_abstract-catalogs/cycle17-abstract-catalog.pdf Дата изменения: Fri May 30 18:19:27 2008 Дата индексирования: Tue Nov 24 21:44:26 2009 Кодировка: Поисковые слова: earth's atmosphere

Cycle 17 Abstract catalog (based on Phase I submissions) Generated on: Fri May 30 08:50:52 EDT 2008 Proposal Category: Scientific Category: ID: Title: PI: PI Institution: GO UNRESOLVED STELLAR POPULATIONS AND GALAXY STRUCTURE 11554 Luminosity Profiles of Extremely Massive Clusters in NGC 7252 Nate Bastian University of Cambridge

The galactic merger remnant NGC 7252 represents one of the most extreme poststarburst environments in the local universe. During the disk-disk merger (~400 Myr ago) this galaxy produced the largest young massive star cluster population known, including two clusters above 10^7 Msun, a factor of 100 more massive than typical globular clusters in the Milky Way. We propose ACS-HRC observations of 3 fields in NGC 7252 in order to explore the detailed properties, i.e. luminosity profiles, of these massive star clusters. These observations will be able to test massive cluster formation mechanisms (e.g. the cluster merger scenario) as well as the possible tidal erosion and truncation of the outer regions of the clusters by the galactic tidal field. These observations will compliment our large on-going study using archival HST data, of star cluster profiles outside the Local Group. The cluster population in NGC 7252 will extend our sample in cluster mass by an order of magnitude. ====================================================================== Proposal Category: Scientific Category: ID: Title: PI: PI Institution: GO COOL STARS 11555 Transition Region and Chromospheric Activity on Low Metallicity Arcturus Moving Group "Alien" Dwarfs Alexander Brown University of Colorado at Boulder

How does low metallicity affect the heating and resultant temperature structure of the chromospheres, transition regions, and coronae of old solarlike dwarf stars? The Arcturus Moving Group is very likely a remnant of the merger of a dwarf galaxy with the Milky Way Galaxy in the distant (~ 7- 8 Gyr) past. This kinematically distinct group has members that are located very close to the Sun, allowing study of stellar activity on very old, low metallicity stars that typically would not be possible. We propose to obtain COS G140L spectra of four dwarf star members of the Arcturus Moving Group to measure the fluxes of their transition region and upper chromospheric emission lines and to investigate the effects of low metallicity on the outer atmospheric radiative losses and temperature structure. Our targets have metallicities of ~ 20% solar or less, spectral types F9 - M4, and are at distances less than 25 pc from the Sun. COS is the only UV spectrograph that is capable of registering the FUV spectra of these stars in a reasonable number of HST orbits. ====================================================================== Proposal Category: GO


Scientific Category: ID: Title: PI: PI Institution:

SOLAR SYSTEM 11556 Investigations of the Pluto System Marc Buie Southwest Research Institute

We propose a set of high SNR observations of the Pluto system that will provide improved lightcurves, orbits, and photometric properties of Nix and Hydra. The key photometric result for Nix and Hydra will be a vastly improved lightcurve shape and rotation period to test if the objects are in synchronous rotation or not. A second goal of this program will be to retrieve a new epoch of albedo map for the surface of Pluto. These observations will also improve masses and in some case densities for the bodies in the Pluto system. ====================================================================== Proposal Category: Scientific Category: ID: Title: PI: PI Institution: GO AGN/QUASARS 11557 The Nature of low-ionization BAL QSOs Gabriela Canalizo University of California - Riverside

The rare subclass of optically-selected QSOs known as low-ionization broad absorption line (LoBAL) QSOs show signs of high-velocity gas outflows and reddened continua indicative of dust obscuration. Recent studies show that galaxies hosting LoBAL QSOs tend to be ultraluminous infrared systems that are undergoing mergers, and that have dominant young (< 100 Myr) stellar populations. Such studies support the idea that LoBAL QSOs represent a short-lived phase early in the life of QSOs, when powerful AGN-driven winds are blowing away the dust and gas surrounding the QSO. If so, understanding LoBALs would be critical in the study of phenomena regulating black hole and galaxy evolution, such as AGN feedback and the early stages of nuclear accretion. These results, however, come from very small samples that may have serious selection biases. We are therefore taking a more aggressive approach by conducting a systematic multiwavelength study of a volume limited sample of LoBAL QSOs at 0.5 < z < 0.6 drawn from SDSS. We propose to image their host galaxies in two bands using WFC3/UVIS and WFC3/IR to study the morphologies for signs of recent tidal interactions and to map their interaction and star forming histories. We will thus determine whether LoBAL QSOs are truly exclusively found in young merging systems that are likely to be in the early stages of nuclear accretion. ====================================================================== Proposal Category: Scientific Category: ID: Title: PI: PI Institution: GO ISM AND CIRCUMSTELLAR MATTER 11558 Planetary Nebulae, Globular Clusters and Binary Mergers Orsola De Marco American Museum of Natural History

Four planetary nebulae (PNe) have been found within 130 of the 150 globular clusters (GCs) of our Galaxy. This might not seem like many, but stellar evolution predicts that the old populations of these clusters should contain


no PN at all ====================================================================== Proposal Category: Scientific Category: ID: Title: PI: PI Institution: GO SOLAR SYSTEM 11559 Jovian Upheaval and its Impact on Vortices Imke de Pater University of California - Berkeley

We propose observations of Jupiter with global coverage at high resolution to quantify changes in its atmosphere during and following the global upheaval. Only HST has the capability to obtain images with enough spatial resolution and contrast to extract velocity fields (we will use our newly developed technique to accomplish this), and with WFC3 we can image Jupiter in its entirety in a single exposure. We are in particular interested in the Red Oval BA: Will the Oval be long-lived, remain red, or turn white again, disappear? Both the merger of its precursors, and change in color has never before been witnessed. The Great Red Spot: This storm system appears to decrease in size and has become rounder, both as derived from its associated cloud deck, but also from its potential vorticity, a more powerful dynamical quantity. How will the GRS evolve? Will it swallow the new vortices detected in amateur images at this same latitude band? How will this effect the potential vorticity? In addition, we hope to understand Disturbances and stagnation points, both of which were detected during the present global upheaval: are these cyclonic regions, can they spawn anticyclones (as suggested by amateur images)? ====================================================================== Proposal Category: Scientific Category: ID: Title: PI: PI Institution: GO COSMOLOGY 11560 Cl0016+1609: the first (and the last) massive cluster of galaxies at z>0.5 Harald Ebeling University of Hawaii

We propose two-filter (F555W, F814W) ACS observations of the core of Cl0016+1609, arguably the most famous massive cluster at z>0.5. The moststudied such system at all wavelengths from X-ray to radio, Cl0016+1609 has no useful multi-passband ACS images to date. Complementing the only existing ACS data (a 2x2 mosaic in the F606W passband and a snapshot of the core in the F775W passband), the observations proposed here will provide resolved color information on both lensed background objects and cluster galaxies, thereby allowing us to measure accurately the cluster's dark-matter distribution on scales from tens to more than 500/h_50 kpc using both strong- and weakgravitational lensing, and to study the color morphology of mergers and the star-formation history of galaxies in a high-density environment. Supported by an extensive groundbased imaging and spectroscopic campaign, as well as by deep Chandra X-ray observations, this observation completes our HST/ACS survey of the 12 most distant galaxy clusters detected in the MACS X-ray survey. ======================================================================


Proposal Category: Scientific Category: ID: Title: PI: PI Institution:

GO EXTRA-SOLAR PLANETS 11561 An intensive COS spectroscopic study of the planetary debris disks around two warm white dwarfs Boris Gaensicke The University of Warwick

It is very likely that the gas giants in our Solar system will survive the evolution of the Sun into a white dwarf, and the same is thought to be generally true for Jovian planets around solar-like stars if their initial orbits are wider than ~3AU. Despite this prediction, no unambiguous detection of a planet around a white dwarf has been announced so far. However, over the past few years, about a dozen white dwarfs have been identified which host metal-rich debris disks that are thought to stem from the tidal disruption of asteroids. In most cases the debris disks are observed in the form of an infrared flux excess, and offer relatively little diagnostic potential for the study of their structure. We have discovered three warm (T~20000K) white dwarfs with metal-rich debris disks in a gaseous phase which display strong double-peaked CaII emission lines in the I-band and weak Fe 5169A emission. The line profiles can be modelled in terms of Keplerian disks with an extension of ~1Rsun around the white dwarfs. Photospheric MgII 4481A absorption demonstrates that the white dwarfs are accreting from the debris disks. Besides these spectral features, the optical wavelength range is devoid of other useful metal transitions. Here, we propose an intensive spectroscopic ultraviolet study of these systems, which will provide (a) ~1000 photospheric absorption lines of 15 chemical elements, allowing an accurate abundance study of the material accreted from the debris disks, and (b) ~2 dozen additional emission lines of Mg, Cr, Ti, and Fe that will provide detailed insight into the dynamical, thermal, and density structure of these exo-planetary debris disks. ====================================================================== Proposal Category: Scientific Category: ID: Title: PI: PI Institution: GO SOLAR SYSTEM 11562 Target of Opportunity Imaging of an Unusual Cloud Feature on Uranus Heidi Hammel Space Science Institute

The planet Uranus is demonstrating increased atmospheric activity as it passes the equinox, likely in response to extreme insolation change. Convective sites in the planet's southern hemisphere reached unprecedented altitudes in 2003 (Hammel et al. 2005, Icarus 175, 284); a bright northern feature showed the highest contrast yet detected in an outer planet atmosphere (Sromovsky et al. 2007, Icarus 192, 558); and a dark atmospheric feature was detected by HST in late 2006 (Hammel et al. 2008, in preparation). The historical record makes references to discrete structures (both bright and dark) on Uranus during previous equinoctial apparitions (the last equinox occurred in 1965). The best amateur facilities are now just able to resolve the disk of Uranus and detect such activity if it is very large or has very high contrast.


Amateurs also have access to a great many nights of telescope time. If a discrete cloud feature on Uranus is reported through the amateur network, we propose to obtain follow-up images with HST's WFC3. The proposed TOO images will permit determination of detailed structure of the feature at visible wavelengths, and will provide vertical and horizontal constraints on the feature's scattering properties. HST is the only facility that can provide such information at visible wavelengths. The proposal was accepted in C16, but not executed because the defined criteria for activation were not met. Because the timescales of change on Uranus are unknown, we resubmit this for Cycle 17. ====================================================================== Proposal Category: Scientific Category: ID: Title: GO COSMOLOGY 11563 Galaxies at z~7-10 in the Reionization Epoch: Luminosity Functions to <0.2L* from Deep IR Imaging of the HUDF and HUDF05 Fields Garth Illingworth University of California - Santa Cruz

PI: PI Institution:

The first generations of galaxies were assembled around redshifts z~7-10+, just 500-800 Myr after recombination, in the heart of the reionization of the universe. We know very little about galaxies in this period. Despite great effort with HST and other telescopes, less than ~15 galaxies have been reliably detected so far at z>7, contrasting with the ~1000 galaxies detected to date at z~6, just 200-400 Myr later, near the end of the reionization epoch. WFC3 IR can dramatically change this situation, enabling derivation of the galaxy luminosity function and its shape at z~7-8 to well below L*, measurement of the UV luminosity density at z~7-8 and z~8-9, and estimates of the contribution of galaxies to reionization at these epochs, as well as characterization of their properties (sizes, structure, colors). A quantitative leap in our understanding of early galaxies, and the timescales of their buildup, requires a total sample of ~100 galaxies at z~7-8 to ~29 AB mag. We can achieve this with 192 WFC3 IR orbits on three disjoint fields (minimizing cosmic variance): the HUDF and the two nearby deep fields of the HUDF05. Our program uses three WFC3 IR filters, and leverages over 600 orbits of existing ACS data, to identify, with low contamination, a large sample of over 100 objects at z~7-8, a very useful sample of ~23 at z~8-9, and limits at z~10. By careful placement of the WFC3 IR and parallel ACS pointings, we also enhance the optical ACS imaging on the HUDF and a HUDF05 field. We stress (1) the need to go deep, which is paramount to define L*, the shape, and the slope alpha of the luminosity function (LF) at these high redshifts; and (2) the far superior performance of our strategy, compared with the use of strong lensing clusters, in detecting significant samples of faint z~7-8 galaxies to derive their luminosity function and UV ionizing flux. Our recent z~7.4 NICMOS results show that wide-area IR surveys, even of GOODS-like depth, simply do not reach faint enough at z~7-9 to meet the LF and UV flux objectives. In the spirit of the HDF and the HUDF, we will waive any proprietary period, and will also deliver the reduced data to STScI. The proposed data will provide a Legacy resource of great value for a wide range of archival science investigations of galaxies at redshifts z~2-9. The data are likely to remain the deepest IR/optical images until JWST is launched, and will provide sources


for spectroscopic followup by JWST, ALMA and EVLA. ====================================================================== Proposal Category: Scientific Category: ID: Title: PI: PI Institution: GO HOT STARS 11564 Optical and Ultraviolet Photometry of Isolated Neutron Stars David Kaplan Massachusetts Institute of Technology

We propose ultraviolet and B-band observations of 5 nearby, thermally emitting neutron stars. These data will measure the Rayleigh-Jeans tails of their spectra, providing a vital complement to X-ray spectroscopy and helping to constrain atmospheric models, working toward the ultimate goal of unraveling the physics of neutron stars. With these data we will have good-quality optical and UV data for the full sample of these objects, allowing detailed comparisons between them. Finally, the data should allow us to measure proper motions for one or two objects, and will serve as the reference data for the remaining objects; such proper motions allow ages to be determined for these objects by tracing them back to likely birth locations. ====================================================================== Proposal Category: Scientific Category: ID: Title: PI: PI Institution: SNAP COOL STARS 11565 A search for astrometric companions to very low-mass, Population II stars Sebastien Lepine American Museum of Natural History

We propose to carry out a SNAPshot search for astrometric companions in a subsample of very low-mass, halo subdwarfs identified within 120 parsecs of the Sun. These ultra-cool M subdwarfs are local representatives of the lowestmass H-burning objects from the Galactic Population II. The expected 3-4 astrometric doubles that will be discovered will be invaluable in that they will be the first systems from which gravitational masses of metal-poor stars at the bottom of the main sequence can be directly measured. ====================================================================== Proposal Category: Scientific Category: ID: Title: PI: PI Institution: GO SOLAR SYSTEM 11566 Imaging Saturn's Equinoctal Auroras Jonathan Nichols Boston University

Auroral emissions provide an indispensable diagnostic tool for the energetic processes occurring in planetary magnetospheres. In 2009 Saturn will reach equinox for the first time since the advent of high-sensitivity planetary ultraviolet (UV) auroral imaging, offering a unique, transient opportunity to observe both polar auroral regions simultaneously. The observations proposed here will not only provide the best images to date of Saturn's northern


auroras, they will address three fundamental issues: (1) Are Saturn's auroras similar in the north and south? This will reveal the nature of the processes that cause the northern auroras, and verify the multipole nature of Saturn's internal magnetic field. (2) Is the location of the northern auroral emission symmetric with to the south? This will indicate why the southern auroral oval is displaced a few degrees toward midnight from the spin pole. It will also reveal whether the oscillation observed in the location of the southern auroral oval is similarly observed in the north, illuminating the nature of near-planetary period oscillations observed throughout the magnetosphere and potentially providing a value for the elusive rotation period of the deep interior. (3) What is the influence of equinox on the magnetosphere? The unique orientation of the planetary spin axis at equinox will reveal whether the auroras are influenced by the direction of the interplanetary magnetic field, and whether the Sun's effect on Saturn's magnetosphere changes throughout the planet's seasons. The Hubble Space Telescope is the only instrument capable of providing global instantaneous coverage of Saturn's UV auroras, and since Saturn's orbital period is ~30 years, Cycle 17 is the only opportunity to make these observations. ====================================================================== Proposal Category: Scientific Category: ID: Title: PI: PI Institution: SNAP HOT STARS 11567 Boron Abundances in Rapidly Rotating Early-B Stars. Charles Proffitt Computer Sciences Corporation

Models of rotation in early-B stars predict that rotationally driven mixing should deplete surface boron abundances during the main-sequence lifetime of many stars. However, recent work has shown that many boron depleted stars are intrinsically slow rotators for which models predict no depletion should have occurred, while observations of nitrogen in some more rapidly rotating stars show less mixing than the models predict. Boron can provide unique information on the earliest stages of mixing in B stars, but previous surveys have been biased towards narrow-lined stars because of the difficulty in measuring boron abundances in rapidly rotating stars. The two targets observed as part of our Cycle 13 SNAP program 10175, just before STIS failed, demonstrate that it is possible to make useful boron abundance measurements for early-B stars with Vsin(i) above 100 km/s. We propose to extend that survey to a large enough sample of stars to allow statistically significant tests of models of rotational mixing in early-B stars. ====================================================================== Proposal Category: Scientific Category: ID: Title: PI: PI Institution: SNAP ISM AND CIRCUMSTELLAR MATTER 11568 A SNAPSHOT Survey of the Local Interstellar Medium: New NUV Observations of Stars with Archived FUV Observations Seth Redfield University of Texas at Austin

We propose to obtain high-resolution STIS E230H SNAP observations of MgII and FeII interstellar absorption lines toward stars within 100 parsecs that


already have moderate or high-resolution far-UV (FUV), 900-1700 A, observations available in the MAST Archive. Fundamental properties, such as temperature, turbulence, ionization, abundances, and depletions of gas in the local interstellar medium (LISM) can be measured by coupling such observations. Due to the wide spectral range of STIS, observations to study nearby stars also contain important data about the LISM embedded within their spectra. However, unlocking this information from the intrinsically broad and often saturated FUV absorption lines of low-mass ions, (DI, CII, NI, OI), requires first understanding the kinematic structure of the gas along the line of sight. This can be achieved with high resolution spectra of high-mass ions, (FeII, MgII), which have narrow absorption lines, and can resolve each individual velocity component (interstellar cloud). By obtaining short (~10 minute) E230H observations of FeII and MgII, for stars that already have moderate or high-resolution FUV spectra, we can increase the sample of LISM measurements, and thereby expand our knowledge of the physical properties of the gas in our galactic neighborhood. STIS is the only instrument capable of obtaining the required high resolution data now or in the foreseeable future. ====================================================================== Proposal Category: Scientific Category: ID: Title: PI: PI Institution: GO ISM AND CIRCUMSTELLAR MATTER 11569 Probing the Atomic and Molecular Inventory of a Beta-Pic Analog, the Young, Edge-On Debris Disk of HD32297 Seth Redfield University of Texas at Austin

Edge-on, optically thin, debris disks provide unique opportunities to probe physical properties of the disk itself. Using the host star as the background source, trace atomic and molecular disk species can be detected in absorption. Redfield (2007) found that the recently discovered edge-on system, HD32297, has the strongest NaI absorption feature of any known debris disk, 5 times the level observed toward beta Pic, the canonical edge-on debris disk. Roberge et al. (2006) compiled the only comprehensive chemical inventory of a debris disk, using beta Pic, and found that carbon was surprisingly overabundant, which has important implications for the physical structure and support of a stable gas disk. What is severely lacking are comparison observations to determine if such an abundance pattern is typical of debris disk systems. HD32297 represents the best opportunity to make such a comparative study and perform a comprehensive gas inventory of a debris disk, due to its high NaI column density. The UV is critical for this work due to the large number of strong transitions (almost 50 ions and molecules are accessible) that are located in, and often only in, the UV. These observations will provide a much needed comparison dataset for addressing the gas chemistry of debris disk systems that are at the critical stage, near the end of planet formation, and in the process of clearing their interplanetary environments. ====================================================================== Proposal Category: Scientific Category: ID: Title: PI: GO COSMOLOGY 11570 Narrowing in on the Hubble Constant and Dark Energy Adam Riess


PI Institution:

The Johns Hopkins University

A measurement of the Hubble constant to a precision of a few percent would be a powerful aid to the investigation of the nature of dark energy and a potent "end-to-end" test of the present cosmological model. In Cycle 15 we constructed a new, streamlined distance ladder utilizing high-quality type Ia supernova data and observations of Cepheids with HST in the near-IR to minimize the dominant sources of systematic uncertainty in past measurements of the Hubble constant and reduce its total uncertainty to a little under 5%. Here we propose to exploit this new route to reduce the remaining uncertainty by more than 30%, translating into an equal reduction in the uncertainty of the equation of state of dark energy. We propose three sets of observations to reach this goal: a mosaic of NGC 4258 with WFC3 in F160W to triple its sample of long period Cepheids, WFC3/F160W observations of the 6 ideal SN Ia hosts to triple their samples of Cepheids, and observations of NGC 5584 the host of a new SN Ia, SN 2007af, to discover and measure its Cepheids and begin expanding the small set of SN Ia luminosity calibrations. These observations would provide the bulk of a coordinated program aimed at making the measurement of the Hubble constant one of the leading constraints on dark energy. ====================================================================== Proposal Category: Scientific Category: ID: Title: PI: PI Institution: GO AGN/QUASARS 11571 A Fundamental Test of Accretion Physics with NGC 4203 Joseph Shields Ohio University

The rapid evolution of quasars indicates that supermassive black holes in galaxy nuclei spend most of their time in a relatively quiescent state. Studies of nearby galaxies demonstrate that many such black holes are accreting at a low rate, and appear as low-luminosity active galactic nuclei (LLAGNs). Theoretical arguments suggest that the mode of accretion onto a central black hole may be very different in LLAGNs as compared to highluminosity systems. The LINER NGC 4203 provides an excellent opportunity to investigate quantitatively the accretion process in a LLAGN, and hence the typical accretion state for a supermassive black hole. Cycle 7 STIS data acquired at one position angle reveal double-peaked H-alpha emission in the nucleus that may trace an accretion disk, and spatially resolved emission that places an upper limit on black-hole mass. We propose observations with STIS to map the two-dimensional velocity field of the circumnuclear gas disk in the central regions of NGC 4203, in order to measure the black-hole mass. This parameter is essential for testing theoretical models of accretion, determining the mass accretion rate, and estimating the radiative efficiency for accreted matter. The results will be important for making sense of LLAGNs, and for translating their measured luminosity into accretion rates that trace the growth of black holes. This is a resubmission of a proposal that was approved for 5 orbits in Cycle 13 (GO-10191) but never carried out due to the failure of STIS. ====================================================================== Proposal Category: GO


Scientific Category: EXTRA-SOLAR PLANETS ID: 11572 Title: Charaterizing Atmospheric Sodium in the Transiting hotJupiter HD189733b PI: David Sing PI Institution: CNRS, Institut d'Astrophysique de Paris We propose STIS transit observations of the exoplanet HD189733b with the goal of measuring atmospheric atomic sodium. Our strategy is to repeat the observing meathods used for HD209458b, which resulted in a successful exoplanetary atmospheric sodium detection. Initial ground-based measurements suggest that the sodium signature on HD189733 could be up to three times larger than HD209458b, making a robust 8? detection possible within a 12 orbit program observing three transits. Transit transmission spectra resulting from space-based measurements have the advantage of retaining absolute transit depths when features are measured, which will make it possible to provide an observational link between sodium and atmospheric haze detected with ACS. Such a link can break modeling degeneracies and providing stringent constraints on the overall atmospheric properties, making such atmospheric information as abundances and the temperature-pressure-altitude relation known. A successful measurement will also allow for comparative atmospheric exoplanetology, as an atmospheric feature will be measured with the same instrument in two separate planets. ====================================================================== Proposal Category: Scientific Category: ID: Title: PI: PI Institution: GO SOLAR SYSTEM 11573 Investigating Post-Equinox Atmospheric Changes on Uranus Lawrence Sromovsky University of Wisconsin - Madison

Uranus is now past its 7 December 2007 equinox. The large seasonal phase shift expected from its long radiative time constant implies that it should now be in the process of reversing its hemispheric asymmetries in cloud band structure and zonal circulation. Many changes already observed -- the development of the first visible-wavelength dark spot, discovered in Cycle 15, the fading of the south polar cap, and the development of a new northern bright band while the southern band fades -- may all be indicative of the expected reversal. We propose a detailed characterization of Uranus' current seasonal response with a 9-orbit program consisting of 3 orbits of WFC3 imaging of cloud bands and dark spots, and 6 orbits of NICMOS imaging using both broadband and narrowband filters capable of tracking bright discrete cloud features. Filters between 0.467 and 1.87 microns will provide vertical sensing depths scanning through the pressure range where the putative methane and deeper H2S clouds might plausibly exist and provide strong constraints on their contributions and parent gas mixing ratios. These observations have unique combinations of spectral range and resolution with needed temporal sampling and spatial resolution not available from groundbased observations. ====================================================================== Proposal Category: GO Scientific Category: AGN/QUASARS


ID: Title: PI: PI Institution:

11574 Physical Characteristics of the Massive Outflow in 3C 48 Alan Stockton University of Hawaii

Superwinds associated with the triggering of quasars are of current interest because such feedback effects may be connected with the initial formation of the black-hole-mass/bulge mass correlation. In the z = 0.369 compact-steepspectrum quasar 3C48, ground-based IFU observations show the presence of a high-velocity, wide-solid-angle outflow of gas, apparently connected with the recent formation of the radio jet. The total mass of gas in this outflow is at least 10^9 solar masses, but it could be well over 10^10 solar masses (i.e., similar to or greater than the total interstellar mass of the Milky Way) if most of the gas has densities like those seen in other quasar extended emission regions. To determine the physical state and energetics of the gas in the outflow, we request (1) high-spatial-resolution spectroscopy over a wide spectral range, including the near UV, and (2) medium-resolution spectroscopy of the strong [O III] 5007 line, which, when combined with unpublished archival data, will allow complete coverage of the velocity field of the high-velocity gas in the inner region. ====================================================================== Proposal Category: Scientific Category: ID: Title: PI: PI Institution: GO HOT STARS 11575 The Stellar Origins of Supernovae Schuyler Van Dyk Jet Propulsion Laboratory

Supernovae (SNe) have a profound effect on galaxies, and have been used recently as precise cosmological probes, resulting in the discovery of the accelerating Universe. They are clearly very important events deserving of intense study. Yet, even with nearly 4000 known SNe, we know relatively little about the stars which give rise to these powerful explosions. The main limitation has been the lack of spatial resolution in pre-SN imaging data. However, since 1999 our team has been at the vanguard of directly identifying SN progenitor stars in HST images. From this exciting new line of study, the emerging trend from 5 detections for Type II-Plateau SNe is that their progenitors appear to be relatively low mass (8 to 20 Msun) red supergiants, although more cases are needed. Nonetheless, the nature of the progenitors of Type Ib/c SNe, a subset of which are associated with the amazing gamma-ray bursts, remains ambiguous. Furthermore, we remain in the continually embarrassing situation that we still do not yet know which progenitor systems explode as Type Ia SNe, which are currently being used for precision cosmology. In Cycle 16 we have triggered on the Type Ic SN 2007gr so far. We propose to determine the identities of the progenitors of 4 SNe within 17 Mpc, which we expect to occur during Cycle 17, through ToO observations using ACS/HRC. ====================================================================== Proposal Category: GO Scientific Category: EXTRA-SOLAR PLANETS ID: 11576


Title: PI: PI Institution:

Physical parameters of the upper atmosphere of the extrasolar planet HD209458b Alfred Vidal-Madjar CNRS, Institut d'Astrophysique de Paris

One of the most studied extrasolar planet, HD209458b, has revealed both its lower and upper atmosphere thanks to HST and Spitzer observatories. Through transmission spectroscopy technique, several atmospheric species were detected: NaI, HI, OI and CII. Using STIS archived transit absorption spectrum from 3000 to 8000 Angstrom, we obtained detailed constraints on the vertical profile of temperature, pressure and abundances (Sing et al 2008a, 2008b, Lecavelier et al. 2008b). By observing in the NUV, from 2300 to 3100 Angstrom, we expect to obtain new constraints on the physical conditions and the chemical composition of the upper atmosphere: temperature/pressure profile up to very high in the atmosphere, abundance and condensation altitudes of new species, and new insight in the atmospheric escape and ionization state at the upper levels. The observation of four HD209458b transits with a single E230M setting will give access to many NUV atomic lines addressing these issues. The proposed observations will probe, for the first time, in details the atmosphere of a hot Jupiter, thus bench marking follow up studies. ====================================================================== Proposal Category: Scientific Category: ID: Title: PI: PI Institution: GO UNRESOLVED STELLAR POPULATIONS AND GALAXY STRUCTURE 11577 Opening New Windows on the Antennae with WFC3 Brad Whitmore Space Telescope Science Institute

We propose to use WFC3 to provide key observations of young star clusters in "The Antennae" (NGC4038/39). Of prime importance is the WFC3's ability to push the limiting UV magnitude FIVE mag deeper than our previous WFPC2 observations. This corresponds to pushing the limiting cluster mass from ~10**5 to ~10**3 solar masses for cluster ages ~10**8 yrs. In addition, the much wider field of view of the WFC3 IR channel will allow us to map out both colliding disks rather than just the Overlap Region between them. This will be especially important for finding the youngest clusters that are still embedded in their placental cocoons. The extensive set of narrow-band filters will provide an effective means for determining the properties of shocks, which are believed to be a primary triggering mechanism for star formation. We will also use ACS in parallel with WFC3 to observe portions of both the northern and southern tails at no additional orbital cost. Finally, one additional primary WFC3 orbit will be used to supplement exisiting HST observations of the star-forming "dwarf" galaxy at the end of the southern tail. Hence, when completed we will have full UBVI + H_alpha coverage (or more for the main galaxy) of four different environments in the Antennae. In conjunction with the extensive multi-wavelength database we have collected (both HST and ground-based) these observations will provide answers to fundamental questions such as: How do these clusters form and evolve? How is star formation triggered? How do star clusters affect the local and global ISM, and the evolution of the galaxy as a whole? The Antennae galaxies are the nearest example of a major disk--disk merger, and hence may represent our best chance for understanding how mergers form tremendous numbers of clusters and stars,


both in the local universe and during galaxy assembly at high redshift. ====================================================================== Proposal Category: Scientific Category: ID: Title: PI: PI Institution: GO UNRESOLVED STELLAR POPULATIONS AND GALAXY STRUCTURE 11578 The Extremely Metal-Poor BCD Galaxy DDO 68: a Young Galaxy in the Local Universe ? Alessandra Aloisi Space Telescope Science Institute - ESA

A long standing question in astrophysics is the existence of young galaxies, in which stars are now forming for the first time, in the nearby (i.e., present-day) universe. Such galaxies would be the local analogs of primordial galaxies observed at high redshift. The most promising candidates have long been the most metal-poor systems, including dwarf irregulars (dIrrs) and blue compact dwarfs (BCDs). However, in many dIrrs and BCDs studied with HST an old (> 1 Gyr) underlying stellar population, as traced by red giant branch (RGB) stars, has been unambiguously detected. Even in I Zw 18, which is the mostmetal poor prototype of the class and long the most controversial case, our group has recently succeeded in detecting an RGB. Nonetheless, there remains the possibility that the star formation histories of BCDs/dIrrs vary from galaxy to galaxy, and that truly young galaxies do exist in the local universe. A new test of these issues has only recently become possible with the identification of DDO 68 as an extremely metal-poor galaxy with an oxygen abundance equal to that of I Zw 18 (12+(O/H)=7.21). This galaxy is about a factor of 2-3 closer than I Zw 18, which yields the opportunity to avoid the many ambiguities that have plagued studies of I Zw 18. Also, DDO 68 resides in a void, making it more likely that star formation has been suppressed for a very long time. We propose to observe DDO 68 with ACS/WFC in F606W and F814W, plus F658N (Halpha) to correct the broad F606W for gas contamination, for a total of 7 orbits. We will use WFC3 in parallel with the same filters to study radial population gradients. Deep color-magnitude diagrams (CMDs) reaching the depth of one magnitude below the predicted RGB tip will be constructed and interpreted based on synthetic CMD fitting. These data will determine unambiguously whether DDO 68 has an underlying old (RGB) stellar population or is forming stars for the first time. Finding just a single nearby ``young'' galaxy would have profound cosmological implications. ====================================================================== Proposal Category: Scientific Category: ID: Title: PI: PI Institution: GO ISM IN EXTERNAL GALAXIES 11579 The Difference Between Neutral- and Ionized-Gas Metal Abundances in Local Star-Forming Galaxies with COS Alessandra Aloisi Space Telescope Science Institute - ESA

The metallicity of galaxies and its evolution with redshift is of paramount importance for understanding galaxy formation. Abundances in the interstellar medium (ISM) are typically determined using emission-line spectroscopy of HII regions. However, since HII regions are associated with recent SF they may not have abundances typical for the galaxy as a whole. This is true in particular


for star-forming galaxies (SFGs), in which the bulk of the metals may be contained in the neutral gas. It is therefore important to directly probe the metal abundances in the neutral gas. This can be done using absorption lines in the Far UV. We have developed techniques to do this in SFGs, where the absorption is measured for sightlines toward bright SF regions within the galaxy itself. We have successfully applied this technique to a sample of galaxies observed with FUSE. The results have been very promising, suggesting in I Zw 18 that abundances in the neutral gas may be up to 0.5 dex lower than in the ionized gas. However, the interpretation of the FUSE data is complicated by the very large FUSE aperture (30 arcsec), the modest S/N, and the limited selection of species available in the FUSE bandpass. The advent of COS on HST now allows a significant advance in all of these areas. We therefore propose absorption line spectroscopy with G130M in the same sample for which we already have crude constraints from FUSE. We will obtain ACS/SBC images to select the few optimal sightlines to target in each galaxy. The results will be interpreted through line-profile fitting to determine the metal abundances constrained by the available lines. The results will provide important new insights into the metallicities of galaxies, and into outstanding problems at high redshift such as the observed offset between the metallicities of Lyman Break Galaxies and Damped Lyman Alpha systems. ====================================================================== Proposal Category: Scientific Category: ID: Title: PI: PI Institution: GO ISM AND CIRCUMSTELLAR MATTER 11580 Watching Young Planetary Nebulae Grow: "The Movie" Bruce Balick University of Washington

The development of magneto-hydro gas dynamical models is the key to the understanding of both the physics (processes) and astronomy (initial conditions) of astrophysical nebulae of all sorts. The models are reaching their highest degree of accuracy when applied to and compared against pre Planetary Nebulae (pPNe) thanks to the simplicity, relative lack of extinction, and the detail of the imaging and kinematic data that have bcome available for these objects. The primary barrier to progress is inadequate kinematic data of pPNe against which the predictions models can be tested. Unlike PNe, pPNe do not emit emission lines for detailed Doppler measurements. Therefore it is essential to find another way to monitor the morphological evolution. Only HST can uncover the dynamics of the growth patterns by subtracting multi-epoch images spanning a decade or more. We have selected four pPNe with highly collimated outflows in different evolutionary stages for which high-quality first-epoch images were obtained from 1996 to 2002. All of them display regularly shaped thin rims, sharp edges, and symmetric pairs of knots or bowshocks that are ideal for our purposes. We will closely mimic many of the earlier exposures using ACS and to monitor changes in structures. The morphology and its evolution will be compared to 3-D MHD models with adaptive grids in order to build a far clearer picture of the nuclear geometry which shaped the outflows and constrained their propagation to the present. We shall also obtain R, J, and H images for use with a 3-D dust radiative transfer code LELUYA to model the dust distribution deep into the nuclear zones. ======================================================================


Proposal Category: Scientific Category: ID: Title: PI: PI Institution:

GO HOT STARS 11581 Searching for Pulsations from a Helium White Dwarf Companion to a Millisecond Pulsar Lars Bildsten University of California - Santa Barbara

The low mass white dwarf (WD) companion to the 3.26 ms pulsar PSR J1911-5958A offers an unprecedented opportunity for seismological study of the interior of a helium core WD. While much more massive carbon/oxygen core WDs are observed to pulsate in normal modes of oscillation called g-modes (known as ZZ Ceti stars), no helium core pulsator is known. By extrapolating the boundaries of the ZZ Ceti instability strip downward in surface gravity by a factor of 20 below any known pulsator, we find that the effective temperature of this WD makes it an excellent candidate to search for pulsation. Detection of g-mode pulsations in the lightcurve would have a transformative effect on the field of WD pulsations, as this would allow the first seismological study of the interior of a helium core WD, and the low gravity strongly constrains theories for the driving and amplitudes of pulsations. We show that with 3 orbits of HST, we will detect photometric variations with amplitudes of 1%, lower than typically seen in other hydrogen-dominated ZZ Ceti stars. A set of measured mode periods would also constrain the thickness of the presumed stably hydrogen burning shell, and help us determine its age more securely. ====================================================================== Proposal Category: Scientific Category: ID: Title: PI: PI Institution: GO COSMOLOGY 11582 The spatial distribution of radiation in the complex ISM of distant ultraluminous galaxies Andrew Blain California Institute of Technology

A significant fraction of energy emitted by galaxies at redshifts when their stars were forming most vigorously, and when their blackholes were growing most powerfully emerges at far-infrared (IR) wavelengths. The fraction of this energy generated by the most extreme and luminous objects is also much larger than the equivalent fraction at optical wavelengths. Many of the most luminous far-IR sources have been located precisely and unambiguously using deep radio, Spitzer and optical observations, and have spectroscopic identifications using the largest ground-based telescopes. Surprisingly, however, the spectra of most of these heavily dust-enshrouded galaxies show prominent Lyman-alpha emission. We propose to observe five of the brightest examples at z~2-3 in reactivated ACS ramp filters, to resolve the spatial distribution of this line emission on fine kpc scales, in order to contrast and compare with the underlying ultraviolet (UV) continuum. Precise spectroscopic redshifts and the unique rest-UV resolution of HST are both essential to reveal the escape and generation of Lyman-alpha photons in the dusty ISM of these extreme galaxies. There is no other way to trace the detailed spatial distirbution of the most excited gas in a galactic wind, along with emission from less-massive starforming galaxies in associated groups. The targets have available HST-


resolution ground-based near-IR AO imaging and arcsec-scale images in CO from ground-based mm-wave interferometers, which provide context for spatial structure of evolved stars and the ISM. The interplay between restframe UV emission and the ISM in these galaxies has important consequences for understanding the origin of the prodigous luminosity of these systems, and for future observations with JWST and ALMA. ====================================================================== Proposal Category: Scientific Category: ID: Title: PI: PI Institution: GO UNRESOLVED STELLAR POPULATIONS AND GALAXY STRUCTURE 11583 The Star Formation Rate In Nearby Elliptical Galaxies Joel Bregman University of Michigan

Small amounts of star formation in normal elliptical galaxies are suggested by several results: some surprisingly young ages from optical line-index dating; cooling X-ray gas; and mid-IR dust emission. Previously, it was difficult to detect low levels of star formation, but UV imaging with WFPC3 will permit us to conclusively identify individual O/B stars in nearby normal ellipticals by their UV colors and magnitudes. This technique is orders of magnitude more sensitive than previous methods, allowing detections of star formation to levels of 1E-4 Msolar/yr. Proof of concept is provided by a very long UV ACS observation of M87 that revealed many O/B stars. We propose observations of four normal ellipticals where recent star formation is likely. This will yield their star formation rates and the locations of such activity. ====================================================================== Proposal Category: Scientific Category: ID: Title: PI: PI Institution: GO RESOLVED STELLAR POPULATIONS 11584 Resolving the Smallest Galaxies with ACS Kristin Chiboucas University of Hawaii

An order of magnitude more dwarf galaxies are expected to inhabit the Local Group, based on currently accepted galaxy formation models, than have been observed. This discrepancy has been noted in environments ranging from the field to rich clusters, with evidence emerging that lower density regions contain fewer dwarfs per giant than higher density regions, in further contrast to model predictions. However, there is no complete census of the faintest dwarf galaxies in any environment. The discovery of the smallest and faintest dwarfs is hampered by the limitations in detecting such compact or low surface brightness galaxies, and this is compounded by the great difficulty in determining accurate distances to, or ascertaining group membership for, such faint objects. The M81 group provides a powerful means for establishing membership for faint galaxies in a low density region. With a distance modulus of 27.8, the tip of the red giant branch (TRGB) appears at I ~ 24, just within the reach of ground based surveys. We have completed a 65 square degree survey in the region around M81 with the CFHT/MegaCam. Half of our survey was completed before Cycle 16 and we were awarded time with WFPC2 to observe 15 new candidate dwarf galaxy group members in F606W and F814W bands in order to construct color-magnitude diagrams from which to


measure accurate TRGB distances and determine star formation and metallicity histories. The data obtained show that 8 - 9 of these objects are galaxies at the same distance as M81. In completing our survey, we have discovered an additional 8 candidate galaxies we propose to image with ACS in order to measure TRGB distances and establish membership. We also wish to re-observe our smallest candidate group member and a tidal dwarf candidate with deeper observations made possible with ACS. Once membership has been established for this second set of candidates, we will have a complete census of the dwarf galaxy population in the M81 group to M_r ~ -10, allowing us to obtain a firm measurement of the luminosity function faint-end slope, and, combined with previous HST data, to provide a complete inventory of the age and abundance properties for the collapsed core of the M81 group. ====================================================================== Proposal Category: Scientific Category: ID: Title: PI: PI Institution: GO QUASAR ABSORPTION LINES AND IGM 11585 Tracing the distribution of gas and galaxies using three closely-spaced background QSOs Neil Crighton University of Durham

The distribution of the gaseous intergalactic medium (IGM) around galaxies is fundamentally important to our understanding of galaxy evolution. Simulations suggest that 'feedback' - the return of gas and radiation to the IGM via active galactic nuclei or star-formation-driven winds - is an important part of galaxy formation and a possible way to enrich the IGM with metals. We propose to use COS to observe the IGM towards the brightest known group of three QSOs (z=0.96, 0.96 and 0.73) separated by a few arcminutes on the sky. Using far-UV spectra of the Lyman-alpha forest region at resolutions > 20000, we will detect both the cooler photo-ionized IGM at ~10,000K using narrow HI absorbers, and the warm-hot intergalactic medium (WHIM) at ~100,000 K using OVI and broad HI absorbers over a redshift range of 0 < z < 0.48 (HI) and 0.17 < z < 0.73 (OVI). The immediate objective is to compare the distribution of the WHIM and cooler IGM to the distribution of galaxies in the same field over redshifts from 0 to 0.6, and scales from ~100 kpc to ~1 Mpc. In particular we will look for signs of feedback, such as metal-enriched WHIM gas close to galaxies. The three sight-lines with separations of ~400 kpc to ~1 Mpc will allow us to constrain the size and geometry of gas overdensities in the IGM, which is not possible with only one or two QSO sight-lines. The QSO separations are ideally suited for this purpose, as they are comparable to the expected size of IGM gas clouds. Using state-of-the art hydrodynamical simulations, which include gas cooling inflows, outflows, feedback, and the introduction of gas and metals in the IGM, we will construct mock spectra and galaxy distributions to compare with the observations. Taken together, our new HST observations, ground-based galaxy redshift survey, and simulations will enable us to investigate the nature and extent of the connection between the IGM and galaxies. ====================================================================== Proposal Category: GO Scientific Category: RESOLVED STELLAR POPULATIONS ID: 11586


Title: PI: PI Institution:

Exceptional Galactic Halo Globular Clusters and the Second Parameter Aaron Dotter Dartmouth College

We propose to obtain deep ACS/WFC images of six globular clusters (five of which have no previous HST photometry) that reside in the Galactic halo where the second parameter effect is most pronounced. These globular clusters are among the least studied in the Galaxy and yet, from the perspective of the second parameter problem, the most intriguing. With the best available CMDs only reaching the vicinity of the main sequence turn off at present, the unique sensitivity and resolution of ACS will yield ages of unprecedented precision for these clusters. These data will provide us with new insight into the stellar populations present in the outer Galactic halo and the nature of the second parameter. The second parameter plays a critical role in our understanding of the formation and evolution of the Galaxy and the proposed observations will shed new light on this problem and these exceptional clusters. ====================================================================== Proposal Category: Scientific Category: ID: Title: PI: PI Institution: GO COSMOLOGY 11587 Probing Population III Star Formation in a z=7 Galaxy Xiaohui Fan University of Arizona

Population III (Pop III) stars, the first generation, metal-free stars in the Universe, have been a main focus of the studies of early galaxy formation and reionization. HeII 1640 emission originates from energetic ionizing photons beyond 54.4eV, and is an ideal tracer of massive Pop III star formation with strong far-UV radiation. HeII has not yet been detected directly in individual galaxies at z<6.3, indicating a small contribution of Pop III star formation at those redshifts. We propose to use WFC3 narrow-band imaging to measure the flux of HeII emission in galaxy IOK-1 (z=6.96), the highest redshift spectroscopically confirmed galaxy to date. At this redshift, the HeII line is perfectly located in the WFC3 F130N filter passband. Our deep narrow-band imaging will detect a HeII flux down to 4x10^-18 erg/s/cm^2 at the 5-sigma level, corresponding to a star formation rate from massive Pop III stars of ~1 M_sun per year, a factor of ~5 improvement to the best groundbased results at lower redshift. Strong HeII emission, if detected, will provide the first direct evidence of significant Pop III formation in early galaxies at the end of the reionization epoch. We will also carry out short F125W broad-band observations to measure the rest-frame UV flux of this galaxy in order to constrain its total star formation rate and to provide continuum subtraction for narrow-band imaging. ====================================================================== Proposal Category: Scientific Category: ID: Title: PI: SNAP COSMOLOGY 11588 Galaxy-Scale Strong Lenses from the CFHTLS survey Raphael Gavazzi


PI Institution:

CNRS, Institut d'Astrophysique de Paris

We aim to investigate the origin and evolution of early-type galaxies using gravitational lensing, modeling the mass profiles of objects over a wide range of redshifts. The low redshift (z = 0.2) sample is already in place following the successful HST SLACS survey; we now propose to build up and analyse a sample of comparable size (~50 systems) at high redshift (0.4 < z < 0.9) using HST WFC3 SNAPSHOT observations of lens systems identified by the SL2S collaboration in the CFHT legacy survey. ====================================================================== Proposal Category: Scientific Category: ID: Title: PI: PI Institution: GO RESOLVED STELLAR POPULATIONS 11589 Hypervelocity Stars as Unique Probes of the Galactic Center and Outer Halo Oleg Gnedin University of Michigan

We propose to obtain high-resolution images of 11 new hypervelocity stars in the Galactic halo in order to establish the first-epoch astrometric frame, as a part of a long-term program to measure precise proper motions in an absolute inertial frame. The origin of these recently discovered stars with extremely large positive radial velocities, in excess of the escape speed from the Galaxy, is consistent only with being ejected from the deep potential well of the massive black hole at the Galactic center. Reconstructing the full threedimensional space motion of the hypervelocity stars, through astrometric proper motions, provides a unique opportunity to measure the shape and orientation of the triaxial dark matter halo. The hypervelocity stars allow determination of the Galactic potential out to 120 kpc, independently of and at larger distances than is afforded by tidal streams of satellite galaxies such as the Sagittarius dSph galaxy. Proper motions of the full set of hypervelocity stars will provide unique constraints on massive star formation in the environment of the Galactic center and on the history of stellar ejection by the supermassive black hole. We request one orbit with WFC3 for each of the 11 hypervelocity stars to establish their current positions relative to background galaxies. We request a repeated observation of these stars in Cycle 19, which will conclusively measure the astrometric proper motions. ====================================================================== Proposal Category: Scientific Category: ID: Title: PI: PI Institution: GO HOT STARS 11590 Observing the IR Catastrophe in a Deflagration Type Ia Supernova Saurabh Jha Rutgers the State University of New Jersey Type Ia supernova (SN Ia) cosmology. While there is explosions of white dwarfs, well-understood. Recently, explosions limits our broad agreement that the details of the we have identified an

Our lack of understanding of confidence in their use for these objects represent the explosion mechanism are not


internally homogeneous subclass of SNe Ia whose photometric and spectroscopic peculiarities make them quite distinct from normal SNe Ia. Models suggest we may be seeing the result of an explosion with a subsonic burning front, called a deflagration. We propose to test SN Ia models by obtaining late-time photometry for SN 2008A, a recent, nearby example of this subclass, using ACS and WFC3 on HST. We will accurately measure the late-time photometric decline rate and spectral energy distribution (SED). These observations will allow us to test whether the ejecta contain the large amount of oxygen predicted by certain models. We also aim to detect major evolution of the SED expected due to the "IR catastrophe," a change in the dominant cooling mechanism in the ejecta, as generically predicted by models but only hinted at by current observations. ====================================================================== Proposal Category: Scientific Category: ID: Title: PI: PI Institution: GO COSMOLOGY 11591 Are Low-Luminosity Galaxies Responsible for Cosmic Reionization? Jean-Paul Kneib Laboratoire d'Astrophysique de Marseille

Our group has demonstrated that massive clusters, acting as powerful cosmic lenses, can constrain the abundance and properties of low-luminosity starforming sources beyond z~6; such sources are thought to be responsible for ending cosmic reionization. The large magnification possible in the critical regions of well-constrained clusters brings sources into view that lie at or beyond the limits of conventional exposures such as the UDF. We have shown that the combination of HST and Spitzer is particularly effective in delivering the physical properties of these distant sources, constraining their mass, age and past star formation history. Indirectly, we therefore gain a valuable glimpse to yet earlier epochs. Recognizing the result (and limitations) of blank field surveys, we propose a systematic search through 10 lensing clusters with ACS/F814W and WFC3/[F110W+F160W] (in conjunction with existing deep IRAC data). Our goal is to measure with great accuracy the luminosity function at z~7 over a range of at least 3 magnitude, based on the identification of about 50 lensed galaxies at 6.53 kpc Nicolas Lehner University of Notre Dame

Cosmological simulation predicts that highly ionized gas plays an important role in the formation and evolution of galaxies and their interplay with the


intergalactic medium. The NASA HST and FUSE missions have revealed highvelocity CIV and OVI absorption along extragalactic sightlines through the Galactic halo. These highly ionized high-velocity clouds (HVCs) could cover 85% of the sky and have a detection rate higher than the HI HVCs. Two competing, equally exciting, theories may explain the origin of these highly ionized HVCs: 1) the "Galactic" theory, where the HVCs are the result of feedback processes and trace the disk-halo mass exchange, perhaps including the accretion of matter condensing from an extended corona; 2) the "Local Group" theory, where they are part of the local warm-hot intergalactic medium, representing some of the missing baryonic matter of the Universe. Only direct distance determinations can discriminate between these models. Our group has found that some of these highly ionized HVCs have a Galactic origin, based on STIS observations of one star at z<5.3 kpc. We propose an HST FUV spectral survey to search for and characterize the high velocity NV, CIV, and SiIV interstellar absorption toward 24 stars at much larger distances than any previous searches (4<