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: http://hea-www.harvard.edu/REU/projects04.html
Дата изменения: Unknown Дата индексирования: Mon Oct 1 20:52:38 2012 Кодировка: Поисковые слова: каскад кембла |
------- Advisor's project abstract:
Studying the formation of stars and early evolution of protoplanetary
disks requires sensitive infrared observations. The recently launched
Spitzer Space Telescope is already providing such data on star formation.
One of the three instruments on board Spitzer, IRAC - Infrared Array
Camera, was built at the CfA. In return, we now have over 800 hours
guaranteed time observations. Almost 100 hours of this time is being
dedicated to surveys of star forming regions, including a survey of young
stellar clusters and the Orion Molecular clouds. Spitzer has been taking
science observations since the beginning of December, and we are now
collecting a growing gallery of star forming regions. Each one of these
star forming regions is a snapshot of the cluster forming process, by
obtaining many snapshots covering a range of ages and environments, we
hope to disentangle the complex feedback mechanisms which may occur in
these regions.
As a project, the student will be assigned a star forming region in the
Orion molecular cloud containing a cluster of young stars. Using Spitzer
data, the student will identify stars with disks and protostars in this
cluster, and compare their region with other star forming regions in our
database.
More information can be found at:
------- Advisor's project abstract:
In addition, the student will help us evaluate the effectiveness of
different DEM image display options, including single
temperature emission maps and time-progression DEM movies.
------- Advisor's project abstract:
Chandra observations have also shown that radio sources at the centers
of many cooling flow clusters have inflated large cavities in the
X-ray emitting gas. When these "bubbles" rise buoyantly through the
gas, their energy (enthalpy) is converted to heat in their wakes.
This form of heating is substantial, but insufficient to replace
radiative losses in most cases. Recently, weak shocks, driven by the
expanding radio lobes, have also been detected surrounding the radio
lobes in several systems. In each of the three cases analyzed so far,
the energy of the shocks is more than adequate to make up for the
radiative losses from the cooling flow. In two of them the energy is
significant for heating the whole cluster, showing that shock heating
by active galactic nuclei could play a significant role in the overall
energetics of clusters of galaxies.
Depending on interests, a student will do some of the following:
search the Chandra archives for more examples of shocks generated by
expanding radio lobes; analyze Chandra data for a system of shocks to
determine their basic physical properties, particularly age and total
energy; investigate the histories of energy input to the shocks,
subject to the observed constraints, especially preservation of
abundance gradient.
------- Advisor's project abstract:
Observationally, symbiotic binary stars can suddenly brighten in the
optical, and then slowly fade. But the cause of these 'outbursts' is
not well understood. They could be due to an instability in the
accretion disk around the white dwarf, a change in the rate of nuclear
burning on the surface of the white dwarf, expansion of the white-dwarf
photosphere, or some combination of all of these effects.
We have been collecting weekly optical brightness measurements of five
interesting X-ray-bright southern symbiotic stars. The goal the
intern's project will be to examine these data and 1) see if we have
found any new outbursts, 2) analyze any new outbursts in an attempt to
constrain physical mechanisms, and 3) generally characterize the
optical variability properties (including searching for periodic
variations which could be associated with the orbital motion) of these
five systems.
------- Advisor's project abstract:
We are currently collaborating with GSFC, Brown University and
NIST (CO) to develop magnetic microcalorimeter detectors for
use in future X-ray astromony space missions.
The proposed project will involve the student in the fabrication
and characterization of materials and devices which is necessarily
an interdisciplinary experience. Several areas including: physics,
astronomy, materials science and engineering are applicable in this
project.
------- Advisor's project abstract:
E/S0 galaxies essentially have 2 components to their X-ray emission:
point sources (read: X-ray binaries) and diffuse emission from hot
gas. The point source emission scales with the blue optical
luminosity; the diffuse emission appears to follow a different
relation. The low-luminosity E/S0s (L_B < 10.5) are expected to be
devoid of diffuse emission, yet several show considerable quantities
of hot gas.
Archival Chandra observations of a few low-luminosity E/S0 will be
analyzed to extract the diffuse emission. The spatial distribution
will be extracted and fit with an appropriate profile function. Fit
values will be correlated with E/S0 galaxy parameters to examine the
role of the expected dominant contributors (mass, age, etc.). One
model, for example, implies that the X-ray surface brightness profile
should depend on the wind state of the galaxy.
------- Advisor's project abstract:
Data: 8 roughly 8ksec observations with Chandra Acis-S in CC mode.
4 obs. during X-ray High State and 4 obs during X-ray low state of
the roughly 60 day superorbital period.
SMC X-1 is part of a massive X-ray binary system with 0.7 second
pulses. It is one of only two known sources to show both pulses
and bursts. It is also the only X-ray pulsar for which no spin-down
episodes have been observed. This suggests that SMC X-1 has a
magnetic moment that is an order of magnitude lower than those of
typical X-ray pulsars. Observations with less sensitive instruments
suggest that the pulse profile changes dramatically between high and
low X-ray states. ACIS-S in CC mode is ideal for determining pulse
profiles and conducting pulse phased spectroscopy. We have determined
the pulse period with great accuracy from this data. However, it is
important to conduct a systematic study of pulse profile as a function
of orbital phase, superorbital phase, and energy.
------- Advisor's project abstract:
Galaxies detected at mid-infrared wavelengths are believed to be
important contributors to the total star formation in the universe,
and thus to the cosmic infrared background. Yet the nature of these
galaxies -- dusty elliptical galaxies, star-forming spirals, or
`train-wreck' mergers -- has remained elusive because of the
small areas and limited spatial resolution of previous mid-IR surveys.
We how have a huge sample of mid-infrared galaxies from a survey
done with the IRAC instrument on the Spitzer Space Telescope.
Combining this with a published catalog of morphological parameters
measured from Hubble Space Telescope observations of the region
will help in the understanding of the nature of this population
of galaxies.
------- Advisor's project abstract:
The new Spitzer Space Telescope provides unprecedented spatial
resolution and sensitivity for studying the properties of nearby
galaxies in the mid- to far-IR. The goal of this project is to try to
detect AGN activity in several dozen nearby galaxies -- of a wide
range of morphological types and luminositie s - -- imaged at 3 <
lambda < 160 um with Spitzer. The AGN will be identified in two
different ways: (1) spatially, by fitting 1-D/2-D models to the light
distributions, thereby looking for a point source in the nucleus; and
(2) by looking for nuclear regions significantly redder than the inner
bulges, via 1-D surface brightness profiles. The sensitivity to AGN
activity measured by these methods will be estimated using simple, 2-D
model galaxy simulations. The AGN detections/fluxes will be compared
to Chandra X-ray Observatory data, either through literature searches
or by analysis of archival data (where appropriate) . They will also
be compared to the nuclear activity measured for the sample via
optical spectroscopy, as documented in the literature (e.g., Ho,
Filippenko, & Sargent 1995, 1997, ...).
------- Advisor's project abstract:
Direct imaging of stars other then the Sun is crucial for
understanding the structure of stellar atmospheres, their activity and
magnetic fields, and the variability driven by processes such as
periodic pulsation. Surface details cannot be resolved using current
ground- and space-based telescopes and interferometers even for nearby
giant and supergiant stars. We are currently exploring the
possibility of imaging atmospheric structures and studying the
pulsation processes in a set of variable stars including Cepheids and
evolved giants and supergiants using a long-baseline UV-optical
interferometer such as the Stellar Imager (SI). The Stellar Imager is
expected to have a ~500m baseline and will produce images with ~0.1
milliarcseconds angular resolution. SI represents an advance in
resolution of at least two orders of magnitude when compared to the
HST and will thus be an invaluable resource for many areas of
astrophysics, including understanding stellar activity, stellar
magnetic fields, and for estimating cosmological distances.
This project will concentrate on studies of the potential for
interferometric imaging of pulsating atmospheres and stellar surface
structures at UV-optical wavelengths. The work will involve simulations
of a Cepheid atmospheres and of surface brightness distribution,
taking into account the hydrodynamic effects associated with the pulsation
processes and will use results from numerical simulations of red giant
convection structures to carry out interferometric imaging
simulations.
Work Description:
The student will run existing software to produce models of surface
brightness distributions for a set of cases, and will run a
simulator to produce images as seen by the SI interferometer.
A summer intern will also carry out diagnostics studies of the stellar
activity and variability using the results from these simulations.
1) Ryan Anderson's project abstract
PROJECT TITLE: Spitzer Imaging of Young Stellar Clusters:
Surveying Star Forming Regions for Disks and Protostars
ADVISOR: Dr. Tom Megeath
INTERN: Ryan Anderson, University of Michigan
MENTORS: Dr. Lori Allen, Dr. Phil Myers
How do stars form? In the last thirty years we have learned that 1.) stars
form in cold molecular clouds, 2.) that stars form not in isolation, but
in clusters, and 3.) that most stars form with circumstellar disks - these
disks are the progenitors of solars systems like are own. However, there
is still much to learn. The fact that stars form in dense clusters raises
the possibility that interactions between stars may govern the process of
star and planet formation. For example, disks may be destroyed in dense
clusters by radiation and dynamical stripping, thus preventing the
formation of planets.
http://cfa-www.harvard.edu/~tmegeath/cluster_survey.html
2) Debarati Chattopadhyay's project abstract
PROJECT TITLE: Imaging the Solar Corona with the Solar Dynamics Observatory (launch 2008)
ADVISOR: Dr. Mark Weber
INTERN: Debarati Chattopadhyay, Lehigh University
MENTOR: Alana Sette
The Atmospheric Imaging Assembly (AIA) for the Solar
Dynamics Observatory (launch 2008) will provide images
of the whole solar corona in 8 passbands (8 different
temperatures) every 10 seconds, 24 hours a day for
five years. This project will involve the development of
tools to analyze the AIA data stream efficiently.
One of the computationally intensive jobs is to compute
the "differential emission measure" (DEM) of the corona from
the AIA data sets. The DEM defines the amount of plasma
at each temperature along the line of sight in the image.
We will create simulated images of the corona (from a
set of 3-D computations) and process those images to reconstruct
the DEM at each point in the image. Parallel processing techniques
will be applied with the goal of estimating the computation
time required for a full set of 16-Megapixel AIA images.
3) David (Clay) Hambrick, Harvey Mudd College's project abstract
PROJECT TITLE: Shock Heating of Cooling Flow Clusters
ADVISOR: Dr. Paul Nulsen
INTERN: David (Clay) Hambrick, Harvey Mudd College
MENTOR: TBD
X-ray emission that reveals the hot intergalactic gas in clusters of
galaxies also carries away its heat. Near to the center of many rich
clusters, the rate of heat loss is sufficient to cool the gas to low
temperatures many times over since the cluster was formed. These are
known as cooling flow clusters. Despite the heat loss, observations
with Chandra and XMM-Newton show that little of the gas does cool
significantly, so that some heat source must make up for the radiative
losses.
4) Ceceilia Hedrick's project abstract
PROJECT TITLE: Outbursts in Symbiotic Binary Stars
ADVISOR: Dr. Jennifer (Jeno) Sokoloski
INTERN: Ceceilia Hedrick, University of Nebraska
MENTOR: TBD
Symbiotic stars are binary star systems in which a red-giant star and
a white-dwarf star orbit one another. Since the red giant is very
large and puffy, the material at the stellar surface is only
gravitationally bound to the rest of the star very loosely. The
strong radiation field from the red giant can therefore push the
material away in a wind. The companion white dwarf has a very strong
surface gravitational field, and it captures a portion of the
red-giant wind as it passes by. In some cases, the accreted material
forms a disk around th white dwarf.
5) Tyrel Johnson's project abstract
PROJECT TITLE: Development and Fabrication of Magnetic Microcalorimeter Detectors
for Future Space Missions
ADVISOR: Dr. Susanne Romaine
INTERN: Tyrel Johnson, University of Idaho
MENTOR: Ricardo Bruni
6) David Myer's project abstract
PROJECT TITLE: X-ray Emission from E/S0 Galaxies
ADVISOR: Dr. Eric Schlegel
INTERN: David Myer, UC-San Diego
MENTOR: TBD
7) Joseph Neilsen's project abstract
PROJECT TITLE: Pulse Profiles and Phased Spectroscopy of SMC X-1
ADVISOR: Dr. Saeqa Dil (Saku) Vrtilek
INTERN: Joseph Neilsen, Kenyon College
MENTOR: Dr. Bram Boroson
8) Megan Roscioli's project abstract
PROJECT TITLE: Morphologies of mid-infrared galaxies
ADVISOR: Dr. Pauline Barmby
INTERN: Megan Roscioli Haverford College
MENTOR: Dr. Matt Ashby
9) Krystal Tyler's project abstract
PROJECT TITLE: AGN Activity in Nearby Galaxies Detected at Infrared Wavelengths
With the Spitzer Space Telescope
ADVISOR: Dr. Michael Pahre
INTERN: Krystal Tyler, Purdue University
MENTOR: Dr. Giovanni G. Fazio
10) Linda Watson's project abstract
PROJECT TITLE: Study of Stellar Atmospheric Structure and Distance Estimation
using a UV-optical Interferometer in Space
ADVISOR: Dr. Margarita Korovska
INTERN: Linda Watson, University of Florida
MENTORs: Dr. Dimitar Sasselov, Dr. Massimo Marengo
1) Ryan Anderson
University of Michigan
Abstract:
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--- Advisor: Dr. Tom Megeath
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--- Advisor: Dr. Mark Weber
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--- Advisor: Dr. Paul Nulsen
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--- Advisor: Dr. Jennifer (Jeno) Sokoloski
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--- Advisor: Dr. Susanne Romaine
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--- Advisor: Dr. Eric Schlegel
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--- Advisor: Dr. Saeqa Dil (Saku) Vrtilek
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--- Advisor: Dr. Pauline Barmby
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--- Advisor: Dr. Michael Pahre
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--- Advisor: Dr. Margarita Korovska