Cycle 12 Abstract Catalog
Generated April 04, 2003
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Proposal Category: GO
Scientific Category: ISM AND CIRCUMSTELLAR MATTER
ID: 9718
Title: SMC Extinction Curve Towards a Quiescent Molecular Cloud
PI: Francois Boulanger
PI Institution: Institut d'Astrophysique Spatiale
The lack of 2175 A bump in the SMC extinction curve is interpreted as an
absence of small carbon grains. ISO Mid-IR observations support this
interpretation by showing that PAH features are absent in the spectra of SMC
and LMC massive star forming regions. However, the only ISO observation of
an SMC quiescent molecular cloud shows all PAH features, indicating a PAH
abundance relative to large dust grains similar to that of Milky Way clouds.
We identified a reddened B2III star associated with this cloud. We propose to
observe it with STIS. This observation will provide the first measure of the
extinction properties of SMC dust away from star forming regions. It will
allow us to disentangle the effects of metallicity and massive stars on the
SMC extinction curve and dust composition and to assess the relevance of the
SMC bump-free extinction curve to low metallicity and/or starburst galaxies in
general.
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Proposal Category: GO
Scientific Category: STELLAR POPULATIONS
ID: 9719
Title: Search For Metallicity Spreads in M31 Globular Clusters
PI: Terry Bridges
PI Institution: Anglo-Australian Observatory
Our recent deep HST photometry of the M31 halo globular cluster (GC)
Mayall~II, also called G1, has revealed a red-giant branch with a clear
spread that we attribute to an intrinsic metallicity dispersion of at least
0.4 dex in [Fe/H]. The only other GC exhibiting such a metallicity
dispersion is Omega Centauri, the brightest and most massive Galactic GC,
whose range in [Fe/H] is about 0.5 dex. These observations are obviously
linked to the fact that both G1 and Omega Cen are bright and massive GC, with
potential wells deep enough to keep part of their gas, which might have
been recycled, producing a metallicity scatter among cluster stars.
These observations dramatically challenge the notion of chemical homogeneity
as a defining characteristic of GCs. It is critically important to find out
how common this phenomenon is and how it can constrain
scenarios/models of GC formation. The obvious targets are other bright
and massive GCs, which exist in M31 but not in our Galaxy where Omega Cen is
an isolated giant. We propose to acquire, with ACS/HRC, deep imaging of 3
of the brightest M31 GCs for which we have observed velocity dispersion
values similar to those observed in G1 and Omega Cen. A sample of GCs with
chemical abundance dispersions will provide essential information about
their formation mechanism. This would represent a major step for the
studies of the origin and evolution of stellar populations.
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Proposal Category: GO
Scientific Category: GALAXIES
ID: 9720
Title: Age-dating Star Clusters in M101
PI: Rupali Chandar
PI Institution: Space Telescope Science Institute
M101 represents perhaps our best chance to study the stellar population of a
luminous, late type spiral galaxy, due to both its proximity and its face-on
orientation. For these reasons, 13 orbits of HST ACS observing time were
allocated in Cycle 11 to obtain a 4x4 mosaic image of M101 in BVI .
Unfortunately, a degeneracy between age and reddening exists when only these
three bands are available. Hence, we propose to augment these observations by
obtaining WFPC2 U band and ACS H alpha images. This will enable the accurate
determination of ages for the young clusters, secure identifications of 75-100
old globular clusters, and allow a quantitative study of the HII region sizes
and structures. Some of the specific questions we will address are: How do
the young clusters form and evolve? What fraction of the clusters dissolve
and on what timescales? Do clusters evolve with a continuum of properties?
Using WFPC2 and ACS in parallel, and making use of the fact that M101 is in
the CVZ, allows us to greatly enhance the science return of previous HST
observations for the cost of only 4 orbits.
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Proposal Category: GO
Scientific Category: ISM AND CIRCUMSTELLAR MATTER
ID: 9721
Title: The Kinematics and Dynamics of the Material Surrouding
Eta Carinae
PI: Bryan Dorland
PI Institution: United States Naval Observatory
We propose a series of observations using both WFPC2 and ACS/HRC instruments
that will perform astrometric measurements of the ejecta around eta Car. We
will observe ejecta in three distinct regions: the inner (characterized by the
close-in debris such as the Weigelt blobs), the intermediate (primarily the
equatorial disk), and the outer (the homunculus and the North and South Jet
structures). The WFPC2 observations will provide second and third epoch
measurements for previous WFPC2 data producing a significantly increased
temporal baseline (with corresponding decreases in proper motion, date of
origin and 3D orientation errors) and the third epoch observations will allow
for the detection of acceleration and non-radial motion in the ejecta, testing
the canonical hypothesis of ballistic motion. As WFPC2 decommissioning is
fast approaching, we are also proposing a series of simultaneous ACS/HRC
observations in order to provide a calibration link between the WFPC2 and HRC
astrometric frames. We estimate that our proposed series of observations will
require 10 total orbits with 7 dedicated to WFPC2 observations and 3 to
ACS/HRC observations.
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Proposal Category: GO
Scientific Category: COSMOLOGY
ID: 9722
Title: Life in the fast lane: The dark-matter distribution in
the most massive galaxy clusters in the Universe at z>0.5
PI: Harald Ebeling
PI Institution: University of Hawaii
We propose two-filter ACS observations of a complete sample of 12 very X-ray
luminous galaxy clusters at 0.50.5. HST's
unique capabilities will allow us to: 1) measure accurately the clusters' dark
matter distribution on scales from tens to more than 500/h_50 kpc from
observations of strong and weak gravitational lensing, 2) use galaxy-galaxy
lensing to measure the shape, extent, and mass content of the dark-matter
halos of both cluster and field galaxies, and 3) study the color morphology of
mergers and the star formation history of galaxies in a high-density
environment. The proposed observations are complemented by Chandra
observations of all our targets (all 12 awarded, 11 executed to date) which
provide independent constraints on the dark matter and gas distribution in the
cluster cores, as well a by extensive groundbased observations of weak lensing
on yet larger scales, galaxy dynamics, and the SZ effect.
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Proposal Category: GO
Scientific Category: COSMOLOGY
ID: 9723
Title: Deep NICMOS imaging of HDF-South: restframe optical
morphologies of high redshift galaxies
PI: Marijn Franx
PI Institution: Universiteit Leiden
We have obtained ultra-deep Js, H, Ks imaging of the Hubble Deep Field South
WFPC2 field with the VLT, in order to study high redshift galaxies. The Ks-
band data are the deepest obtained to date in any field. We find that the
population of Ks selected galaxies at z=2-4 in HDF-South differs in two
important aspects from previous studies in HDF-North. First, we find several
galaxies which are large and apparently regular in the rest-frame optical,
with more complex rest-frame UV morphologies. These objects resemble large
disk galaxies in the local Universe. Second, we have identified a population
of galaxies with red J-K colors that are extremely faint in the rest-frame UV.
The galaxies have ages of 0.5-2 Gyr and are highly clustered, and may be
progenitors of nearby bulges and early-type galaxies. We propose to obtain a
deep mosaic with the NICMOS/NIC3 camera in the H band, covering the WFPC2
field. The increased depth and spatial resolution of the NICMOS mosaic would
allow us to determine the restframe optical morphologies of a large sample of
high redshift galaxies, in order to study the relative distributions of young
and old stars, to decompose the galaxies in bulges and disks, to measure scale
lengths, and to model the stellar populations of the sub-components. The lack
of large U-dropouts and red galaxies in HDF-North, and the need for larger
samples call for the proposed imaging of HDF-South. We waive all prioprietary
rights.
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Proposal Category: SNAP
Scientific Category: HOT STARS
ID: 9724
Title: Towards a global understanding of accretion physics -
Clues from an UV spectroscopic survey of cataclysmic
variables
PI: Boris Gaensicke
PI Institution: University of Southampton
Accretion inflows and outflows are fundamental phenomena in a wide variety
of astrophysical environments, such as Young Stellar Objects, galactic
binaries, and AGN. Observationally, cataclysmic variables (CVs) are
particularly well suited for the study of accretion processes. We
are currently carrying out a Cycle 11 STIS UV spectroscopic snapshot
survey of CVs to fully exploit the diagnostic potential of these
objects for our understanding of accretion physics. While the data
obtained so far are of excellent quality, the number of targets that will be
observed in Cycle 11 is too small for a statistically significant
analysis (only 19 objects out of our 149 accepted Cycle 11 snapshot targets
have been observed at the time of writing). We propose here to extend this
survey into Cycle 12, building a homogenous database of accretion disc and
wind outflow spectra covering a wide range of mass transfer rates and
binary inclinations. We will analyse these spectra with state-
of-the-art accretion disc model spectra (SYNDISK), testing our current
knowledge of the accretion disc structure, and, thereby, providing new
insight into the so far not well understood process of viscous dissipation.
We will use our parameterised wind model PYTHON for the analysis of the
radiation driven accretion disc wind spectra, assessing the fundamental
question whether the mass loss rate correlates with the disc
luminosity. In addition, our survey data will identify a number of
systems in which the white dwarf significantly contributes to the UV
flux, permitting an analysis of the impact of mass accretion on the
evolution of these compact stars. This survey will triple the number of
currently available high-quality accretion disc / wind outflow / accreting
white dwarf spectra, and we waive our proprietary rights to permit a timely
use of this database.
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Proposal Category: GO
Scientific Category: SOLAR SYSTEM
ID: 9725
Title: The Long-term Observational Record of Uranus' Atmosphere,
its Rings, and its Satellites: the WFPC2-ACS Link
PI: Erich Karkoschka
PI Institution: University of Arizona
Recording the seasonal change of Uranus is a key to understand seasonal
changes in atmospheres due to Uranus' high obliquity. The best record to date
comes from WFPC2 imaging of Uranus since 1994. We propose to image Uranus
simultaneously with similar filters in WFPC2 and ACS so that this record can
be extended with future ACS observations. Without such an observation, the
long-term record of WFPC2 images cannot be linked with any future images
because of Uranus' steep spectral features. Observations of the Uranian rings
over a wide range of sub-solar latitudes allow powerful constraints on
physical parameters, such as separation between ring particles. Our proposed
observations will provide the necessary link between previous WFPC2 images and
future ACS images near the ring-plane-crossing of 2007. The same reasoning
applies to images of Uranian satellites, where a consistent record over a wide
range of sub-solar latitudes yields information about satellite shape and
albedo distribution. Since Cycle 12 is the last Cycle of WFPC2, there will be
no other chance for the proposed observations. The investment of only two
orbits will significantly enhance the scientific value of the previous 45
WFPC2 orbits on Uranus. Only HST has the spatial resolution and photometric
stability for these studies.
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Proposal Category: SNAP
Scientific Category: HOT STARS
ID: 9726
Title: A NICMOS search for obscured supernovae in starburst
galaxies
PI: Roberto Maiolino
PI Institution: Osservatorio Astrofisico di Arcetri
Recent near-IR monitoring campaigns were successful in detecting obscured
supernovae (SNe) in starburst galaxies. The inferred SN rate is much higher
than that obtained in previous optical campaigns, but it is still significanly
lower than expected by the high level star formation of these systems. One
possible explanation for the shortage of SNe is that most of them occur in
the nuclear region, where the limited angular resolution of groundbased
observations prevents their detection. We propose NICMOS SNAP observations of
a sample of starburst galaxies already observed once by NICMOS, with the goal
of exploiting its sensitivity and angular resolution to detect nuclear
obscured SNe which might have been missed by groundbased surveys. These
observation will allow to assess the real SN rate in starbust galaxies and
deliver a sample of SN occurring in the extreme environment of galactic
nuclei. We expect to detect more than 55 SNe (if the whole sample is
observed). If the number of SNe detected in the program is much lower than
expected it would prompt for a revision of our understanding of the relation
between the star formation rate and the SN rate.
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Proposal Category: GO
Scientific Category: COSMOLOGY
ID: 9727
Title: Exploration of the SN Ia Hubble Diagram at z > 1.2
PI: Saul Perlmutter
PI Institution: Lawrence Berkeley National Laboratory
In the spirit of a Treasury proposal, we propose to organize, and deliver to
the astronomical community, non-proprietary follow-up observations of ~10
Type Ia supernovae at 1 1. This would be a clear signature of a
mixed dark-matter and dark-energy universe. Systematic errors in the SNe Ia
result attributed to grey dust or cosmic evolution of the SN Ia peak
luminosity would not show this change of sign. We have obtained a toehold on
this putative ``epoch of deceleration'' with SN 1997ff at z = 1.7, and 3 more
at z > 1 from our Cycle 11 program, all found and followed by HST. However,
this is too important a test to rest on just a few objects, anyone of which
could be subject to a lensed line-of-sight or misidentification. Here we
propose to extend our measurement with observations of twelve SNe Ia in the
range 1.0 < z < 1.5 or 6 such SNe Ia and 1 ultradistant SN Ia at z = 2, that
will be discovered as a byproduct from proposed Treasury and DD programs.
These objects will provide a much firmer foundation for a conclusion that
touches on important questions of fundamental physics.
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Proposal Category: GO
Scientific Category: ISM AND CIRCUMSTELLAR MATTER
ID: 9729
Title: Probing the nature of Type Ia SNe through HST astrometry
PI: Pilar Ruiz-Lapuente
PI Institution: University of Barcelona
Type Ia supernovae are of key importance in cosmology. Empirical relations
allow their use as cosmological standard candles. The generally accepted
picture is that the exploding star is a C+O white dwarf which accretes matter
from a companion in a binary system. However, the nature of the companion is
still unknown. It could either be another WD, or be a giant, subgiant, or
main-sequence star. Calculations have shown that it is possible to distinguish
among those possibilities by the effect that the supernova explosion has on
the companion star. We propose to identify the companion star of the two
historical well-known SNeIa through ACS imaging of the targets. A radial-
velocity study of the stars in those two Galactic SNeIa has been done from
ground-based facilities. To obtain the full motion vector of those stars, we
plan to use ACS for high-resolution astrometry in two different epochs. That
should allow to detect motion imparted during the explosion in the direction
perpendicular to the line of sight, down to a level of a few milliarcsecs/yr.
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Proposal Category: GO
Scientific Category: HOT STARS
ID: 9730
Title: UV Spectroscopy of the Hot, Helium-Core White Dwarf
Companion in HR 1608
PI: Karin Sandstrom
PI Institution: University of California - Berkeley
We propose to observe the FUV spectrum of the hot, helium-core white dwarf in
the binary system HR 1608 in order to determine if there are suitable spectral
lines to obtain a radial velocity orbit for the white dwarf star. The primary
star in this system, with spectral type K0 IV, dominates the spectrum at
visual wavelengths. At a temperature of around 25,000 K, however, the white
dwarf outshines the primary in the UV. The orbital motion of the primary star
has been monitored for seven years with the CfA Digital Speedometer at Oak
Ridge Observatory in Harvard, MA. In addition, the Hipparcos team noted
excess scatter in the astrometric solution which, though unexplained at the
time, we now know to be due to the orbital motion. Combining the astrometric
and spectroscopic data, we have solved for the orbital elements, including the
inclination of the system. In order to obtain a dynamical mass for the star,
the orbital motion of both stars must be observed, thus the need for
monitoring the white dwarf in the UV. As the first step in this endeavor, we
propose to obtain a STIS spectrum of the white dwarf star to discover if there
are spectral lines with which its radial velocity could be measured precisely
enough to calculate a dynamical mass.
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Proposal Category: GO
Scientific Category: ISM AND CIRCUMSTELLAR MATTER
ID: 9731
Title: Kepler's Supernova Remnant: an Imaging Study of the Blast
Wave - Circumstellar Medium Interaction
PI: Ravi Sankrit
PI Institution: The Johns Hopkins University
Kepler's SNR (SN 1604 AD) is the prime example of a young Galactic SNR where
the blast wave is running into the wind of the progenitor star. The
interaction between the blast wave and the inhomogeneous circumstellar medium
gives rise to knots, evolving on a time scale of years, that dominate the
optical emission from the remnant. Also visible in the optical are fainter
Balmer line filaments that exhibit a range of geometries - from normal sheet-
like filaments to more diffuse clumps of emission, the latter unique to this
remnant. We propose to image Kepler's SNR through several narrowband filters
using ACS/WFC and WFPC2. The morphology and ionization structure of the knots
will be obtained from H-alpha, [S II], and [O III] images. We will also
obtain a [N II] image, which is known to be strong and spatially variable in
the remnant. The proposed H-alpha images will be deep enough so that the
physical scales and structure of the Balmer dominated non-radiative shocks can
be investigated. Our data will be a critical part of multiwavelength studies
of Kepler's SNR. They will complement Chandra and XMM X-ray data and VLA
radio data, and provide a significant advance in understanding the processes
of magnetic field amplification and cosmic ray acceleration in SNRs as well as
the evolution and dynamics of the blast wave - circumstellar medium
interaction.
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Proposal Category: GO
Scientific Category: HOT STARS
ID: 9732
Title: Detecting the hottest white dwarf in a dwarf nova: V446
Her as a laboratory for irradiated accretion discs
PI: Matthias Schreiber
PI Institution: Observatoire de Strasbourg
V446 Her (Nova Her 1960) is an object with very unique combination of
properties: it experienced 40 years ago a nova eruption and started regular
dwarf nova outburst activity 10-20 years ago. We suggest that the white
dwarf, heated to several 100.000K during the thermonuclear surface burning
event, suppressed through irradiation of the accretion disc the thermal
instability underlying dwarf nova outbursts for the first 20-30 years
following the nova eruption. The gradual cooling of the white dwarf results in
a continous decrease of the irradiating flux and, as a result, at present the
outer parts of the accretion disc are thermally unstable and produce the
observed dwarf nova outbursts. V446 Her provides, hence, the exceptional
opportunity to study the structure of a strongly irradiated and thermally
unstable accretion disc. To make rigorous use of V446 Her as a laboratory for
irradiated accretion discs, it is mandatory to know the temperature of the
still extremely hot white dwarf illuminating the disc. We propose to obtain
STIS UV spectroscopy of V446 Her in order to detect the photospheric emission
of the white dwarf, and to derive accurately its temperature. With this
parameter at hand, we will be able to determine the dynamical importance of
disc irradiation. Using our HST/STIS data of V446 Her, we will derive an
observational calibration of the essential parameter in the framework of
irradiated accretion discs i.e. the reprocessing efficiency beta, with
considerable importance not only for our understanding of CV's but also of
Super Soft Sources, X-Ray binaries, and AGN.
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Proposal Category: GO
Scientific Category: HOT STARS
ID: 9733
Title: Direct imaging of the progenitors of massive, core-
collapse supernovae
PI: Stephen Smartt
PI Institution: University of Cambridge
Modern supernovae searches in the nearby Universe are discovering large
numbers of SNe which have massive star progenitors (Types II, Ib and Ic). The
extensive HST (and ground-based) image archives of galaxies within ~20Mpc
enables their individual bright stellar content to be resolved. As massive,
evolved stars are the most luminous single objects in a galaxy, the
progenitors of core-collapse SNe should be directly detectable on pre-
explosion images. Within the last two cycles we have set direct mass-limits on
three type II-P supernovae using HST images, and already these can be used to
constrain theoretical models of pre-supernova stellar evolution which predict
which stars cause which of the supernovae types. We request time to continue
this successful project, and require ACS observations of future SNe which are
discovered in galaxies closer than 20Mpc which have pre-explosion HST archive
images available. These ToO observations will allow the SNe to be precisely
positioned on the pre-explosion frames with the required astrometric accuracy
of around 0.05", and allow 3-colour photometry of the surrounding stellar
populations for reddening estimations. The goal of this project is to directly
identify the progenitor stars of core-collapse supernovae. We will compare the
progenitor detections or luminosity limits to our own stellar evolutionary
tracks in order to determine masses or restrictive mass-limits for the
progenitors.
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Proposal Category: GO
Scientific Category: COSMOLOGY
ID: 9734
Title: Leaky IGM at z=6 or Lyman Alpha Galaxy at z=5?
PI: Richard White
PI Institution: Space Telescope Science Institute
We propose to image the z=6.4 quasar SDSS J1148+5251 with the ACS using a
narrow-band ramp filter in the Lyman Beta Gunn-Peterson absorption trough. The
observations will distinguish between two possible explanations for several
weak emission features seen in a long-exposure Keck spectrum. Either there are
high-ionization bubbles in the IGM at z=6 that allow light from the quasar to
leak through the Lyman Beta forest, or there is an intervening Lyman alpha
emitting galaxy at z=5 (as suggested by C IV absorption at the same redshift.)
If there is a galaxy, it may be associated with a lensing mass concentration
at z=5.
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Proposal Category: GO
Scientific Category: GALAXIES
ID: 9735
Title: ACS, NICMOS, and STIS Observations of Three Ongoing
Mergers
PI: Bradley Whitmore
PI Institution: Space Telescope Science Institute
We propose to make ACS (U, B, V, I, H_alpha), NICMOS (J, H, K), and STIS
(long-slit H_alpha) observations of NGC 520, NGC 2623, and NGC 3256, three
merging galaxies in the middle of the Toomre Sequence and currently in the
throes of violent relaxation. Two of these (NGC 2623 and NGC 3256) are the
most IR luminous galaxies in the sequence. Hence, these ongoing mergers are
ideal candidates for studying the triggering mechanism responsible for the
formation of stars and star clusters. The ACS observations will allow us to
age date the star clusters, and reliably distinguish clusters from stars based
on their apparent sizes. They will also be used in conjunction with ground-
based measurements of the stellar velocity dispersion to determine dynamical
masses of the clusters and hence address the question of whether the IMF is
truncated. The NICMOS observations will allow us to penetrate the dust and
answer several fundamental questions such as: What fraction of the young
clusters are hidden by dust? How do these clusters form and evolve? The STIS
observations will allow us to study the kinematics of the young cluster
system and measure the pressure and shock properties which may be triggering
the formation of the clusters. A better understanding of how mergers form
tremendous numbers of clusters and stars in the local universe will help shed
light on processes that were crucial during galaxy assembly in the high-z
universe.
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Proposal Category: GO
Scientific Category: ISM AND CIRCUMSTELLAR MATTER
ID: 9736
Title: Integrated Absorption- and Emission-Line Analysis of
Nebulae
PI: Robert Williams
PI Institution: Space Telescope Science Institute
Serious discrepancies have arisen in CNONe abundance determinations for
galactic nebulae in the past ten years, depending upon which type of emission
lines are used in the analysis: forbidden vs. permitted lines. The cause of
the discrepancies, which can exceed an order of magnitude for some PNe, has
been studied intensively, but is still unknown. Emission line abundances
cannot be considered reliable until the nature of these contradictory results
is understood. We have just developed a technique for integrating
absorption lines into emission analyses for diffuse nebulae that provides an
independent check on the validity of emission-line analyses. It requires high
resolution observations of UV resonance absorption produced by the nebular gas
in imbedded or background stars together with optical spectra of the nebulae.
Such observations currently exist for only one object, IC 418. We propose to
obtain UV spectra of four PNe central stars with STIS that will provide data
necessary to exploit the new technique of integrated abundance determination
that combines both emission and absorption lines.
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Proposal Category: GO
Scientific Category: COOL STARS
ID: 9737
Title: A NICMOS direct imaging search for giant planets around
the seven single white dwarfs in the Hyades
PI: Hans Zinnecker
PI Institution: Astrophysikalisches Institut Potsdam
We propose to use the NIC1 camera on HST to search for massive giant planets
around the known seven single white dwarfs in the nearby Hyades cluster at
sub-arcsec separations. At an age of 625 Myr, the white dwarfs had
protogenitor masses of about 3 solar masses, and massive gaseous giant planets
should have formed in the massive circumstellar disks around these ex Herbig
A0 stars, probably at orbital separations similar or slightly larger than that
of Jupiter (5 AU) in our own solar system. Such planets would have survived
the post-Main Sequence mass loss of the parent star, and would have migrated
outward adiabatically by a factor 4.5, equal to the ratio of initial to final
stellar mass (3Mo/0.66Mo), due to conservation of orbital angular momentum
during the mass loss (AGB and PN) phase. Thus the orbital separation NOW would
be 4.5 x 5 AU = 22.5 AU, which at the distance of the Hyades (45 pc)
corresponds to 0.50 arcsec. Simulations with TinyTim then show that giant
planets at this separation with masses in the range 6-12 Jupiter masses and
apparent J and H magnitudes in the range 20.5-23.3 mag (from Baraffe or
Burrows models) can be spatially resolved around the Hyades white dwarfs.
Their J and H brightnesses are known to be 15 +/- 0.5 mag, implying a median
star-planet brightness ratio of 1000:1 (7.5 mag). This combination of dynamic
range and orbital separation is observable with NICMOS, by subtracting images
taken at two roll angles. Therefore, the proposed near-IR diffraction-limited
observations in the F110W and F160W filters promise to resolve giant planets
around low-mass stars for the first time. If successful, the observations
would also prove that giant planets do form around early-type stars more
massive than the Sun.
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Proposal Category: GO
Scientific Category: SOLAR SYSTEM
ID: 9738
Title: Spectroscopy and Polarimetry of Mars at Closest Approach
PI: James Bell
PI Institution: Cornell University
We propose a coordinated program of spectroscopy, imaging, and
spectropolarimetry of Mars during the August 2003 opposition to study the
composition and physical state of surface materials and airborne aerosols.
The proposed observations include (a) Moderate spectral resolution 290 to 570
nm STIS long-slit push-broom imaging spectroscopy of Mars, to constrain the
properties of airborne aerosol particles and to search for and globally map
iron-bearing minerals that are diagnostic of specific past climatic
conditions; (b) WFPC2 UV-VIS images designed primarily to quantify the effects
of ice and dust aerosols on our STIS spectra; (c) NICMOS near-IR images to
search for and globally map the presence of hydrated surface minerals; and (d)
ACS multispectral polarizer images to provide critical phase function
measurements needed to constrain the physical properties of the Martian
surface layer. The proposed observations are timed to take advantage of the
closest approach of Mars to Earth for the next several hundred years. Images
and spectra will be acquired at a spatial scale comparable to existing
spacecraft orbital spectroscopy data (~10 km/pixel) and in wavelength regions
not sampled by past or current Mars spacecraft instrumentation. These
observations also provide complementary scientific and calibration
measurements in support of current and future NASA and ESA Mars exploration
missions.
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Proposal Category: GO
Scientific Category: GALAXIES
ID: 9739
Title: Are We Missing the Dominant Sites of Star Formation in
Local UV-Bright Starbursts?
PI: Rupali Chandar
PI Institution: Space Telescope Science Institute
We propose to explore the ages, extinctions, and masses of young stellar
clusters in four nearby dwarf starburst galaxies (He 2-10, NGC 5253, NGC 4214,
and IIZw40). We will combine available archival data with new, high
resolution HST observations from the ultraviolet to the infrared. All four
galaxies are known from ground based radio/infrared observations to contain
highly obscured, massive stellar clusters, which dominate the far infrared
flux. Despite the fact that almost all of the infrared flux comes from
regions which are obscured at UV and optical wavelengths, these galaxies are
consistent with the well known correlation between the UV slope (beta) and the
ratio of far infrared flux to ultraviolet flux at 1600 Angstroms. Because
the UV and IR fluxes are decoupled, this observation implies that a simple
foreground screen model, where UV photons from hot stars are reprocessed into
the infrared by local dust, is not the proper interpretation for why these
galaxies follow the beta relation. We propose to investigate the underlying
mechanisms responsible for this observed correlation in these UV bright
galaxies, and explore the implication for high redshift starbursts.
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Proposal Category: SNAP
Scientific Category: ISM AND CIRCUMSTELLAR MATTER
ID: 9740
Title: CIII] Imagery of Planetary Nebulae and HII Regions -- A
Snap Program
PI: Reginald Dufour
PI Institution: Rice University
We propose to undertake a SNAP program of WFPC2 imagery of several planetary
nebulae and extragalactic HII regions with the F185W filter to study the
spatial variation of the CIII] 1909 Angstrom emission lines across the
nebulae. Much of our current knowledge of carbon abundances in planetary
nebulae and HII regions are based on UV spectroscopic observations of this
line yet there have not been any studies of its spatial variations in nebulae
compared to several of the prominent optical lines (e.g. [OIII] 5007
Angstroms). Such observations, coupled with photoionization modeling of the
nebulae, will enable us to assess the utility of using the CIII] line in
abundance calculations of C/O and C/H in nebulae and possibly permit improved
empirical emission-line diagnostic techniques for ionization corrections to
get the elemental carbon abundances from C++/O++ observations based on
CIII]/[OIII] 1909/5007. We also plan to study the spatial variation of the
CIII] 1909 Angstrom collisionally excited lines against the CII 4267 Angstrom
permitted line in many of the nebulae using previous and planned ground-based
longslit echelle spectroscopy coupled with the HST WFPC2 F185W imagery.
================================================================================
Proposal Category: GO
Scientific Category: ISM AND CIRCUMSTELLAR MATTER
ID: 9741
Title: The Exciting Wavelength of Extended Red Emission
PI: Karl Gordon
PI Institution: University of Arizona
We propose to determine the wavelength of the photons which excite Extended
Red Emission (ERE) by mapping the small scale structure of ERE and molecular
hydrogen (H_2) in the reflection nebulae NGC 2023 and 7023. Both of these
nebulae display sharp narrow ERE-filaments within photodissociation regions
(PDR) which also show infrared H_2 fluorescence. In these opically thick
filaments, different wavelength photons penetrate to different depths. By
comparing the widths of these filaments in ERE and H_2 we will determine the
exciting wavelength of ERE. This is possible because the combined opacity of
dust and H_2 to the exciting radiation (lambda < 1100 A) of H_2 fluorescence
is known, and the comparison of the thickness of the ERE and H_2 filaments
will allow a determination of the dust opacity at the wavelength at which ERE
is being excited. This is a sensitive test to distinguish between different
materials which have been proposed as the carrier of ERE (e.g., carbon or
silicon nanoparticles, polycyclic aromatic hydrocarbon molecules, hydrogenated
amorphous carbon, etc.), because the photoluminescense excitation spectra of
these different materials differ by large amounts. Identifying the material
which produces ERE is important as recent work on ERE in the diffuse
interstellar medium has shown that the material which produces ERE comprises a
significant component of dust grains.
================================================================================
Proposal Category: GO
Scientific Category: STAR FORMATION
ID: 9742
Title: Natural Coronagraphic Imaging of KH 15D
PI: William Herbst
PI Institution: Wesleyan University
We propose to obtain V, H-alpha and [SII] images of the unique, eclipsing pre-
main sequence star KH 15D near minimum light with the ACS/HRC. This solar-like
star in NGC 2264, near the Cone Nebula, is fortuitously positioned with
respect to our line of sight. Every 48.36 days its photosphere and accretion
zone are progressively occulted and then revealed by an eclipsing body, which
is evidently non-luminous, extended circumstellar matter in the star's
vicinity. Dramatic spectral evolution is seen during these "natural
cononagraphic" events that is revealing the structure of the accretion zone on
spatial scales (~0.01 AU or less) that may not be achieved in other sources
for decades to come, if ever. It is important to know whether this object is
unique only in its orientation and not in its basic structure. Our
observations will test the hypothesis that KH 15D at minimum light looks like
nearly edge-on disk/jet systems around stars of similar mass and age in closer
star forming regions such as Tau/Aur or MBM 12. We argue that the disk and jet
will be resolved and will provide new constraints on this system. If not
resolved, the data will at least constrain the scattering and jet emission
zones to be remarkably close to the star (~10 AU). In either case, we will
have important new information on the nature of this unique object.
================================================================================
Proposal Category: GO
Scientific Category: ISM AND CIRCUMSTELLAR MATTER
ID: 9743
Title: Multi-wavelength Observations of Symbiotic Stars in
Outburst
PI: Charles Keyes
PI Institution: Space Telescope Science Institute
To investigate the cause and nature of classical symbiotic outbursts, we
initiated a program of multi-wavelength observations of these events. As
evidence is mounting that collimated outflows (jets) may be associated with
symbiotic outbursts, we also investigate conditions needed for jet production
- a question with broad astrophysical relevance. The first target for our
campaign - the 2000-2002 outburst of Z Andromedae - confirmed the utility and
need for coordinated multi-wavelength observations to make progress in
understanding the nature of the outburst mechanisms in symbiotic stars. FUSE
ultraviolet data were the cornerstone of this project (which included data
from the VLA, MERLIN, ground-based spectroscopy and photometry, Chandra, and
XMM, but not HST). Our Z And observations have motivated us to propose a new
scenario which we term the disk-instability trigger. To test this new model,
we propose to continue the multi-wavelength campaign approach with
observations at several epochs during the outburst of a second target-of-
opportunity (TOO). The evolution of the X-ray and UV spectrum throughout the
outburst plays a vital role in distinguishing between the outburst models
currently in contention for describing outburst behavior. Analysis of our
first campaign has shown that HST observations can play a fundamental role in
the multi-wavelength approach. Emission line strengths of the features in the
HST-UV, especially when combined with lines of the same species from the other
spectral regions, provide diagnostics of the colliding wind/shock region. The
combination of high-resolution STIS and FUSE-band absorption features, time-
tagged observations, and continua provide a unique opportunity to probe the
structure and ionization conditions in the outburst material that can not be
accomplished with either ultraviolet region alone.
================================================================================
Proposal Category: GO
Scientific Category: COSMOLOGY
ID: 9744
Title: HST Imaging of Gravitational Lenses
PI: Christopher Kochanek
PI Institution: Smithsonian Institution Astrophysical Observatory
Gravitational lenses offer unique opportunities to study cosmology, dark
matter, galactic structure, galaxy evolution and quasar host galaxies. They
are also the only sample of galaxies selected based on their mass rather than
their luminosity or surface brightness. While gravitational lenses can be
discovered with ground-based optical and radio observations, converting them
into astrophysical tools requires HST. HST has demonstrated that it is the
only telescope that can in each case precisely locate the lens galaxy,
measure its luminosity, color and structure, and search for lensed images of
the source host galaxy given the typical image separations of ~1''. We will
obtain ACS/WFC V and I images and NICMOS H images of 21 new lenses never
observed by HST and NICMOS H images of 16 lenses never observed by HST in the
IR. As in previous cycles, we request that the data be made public
immediately.
================================================================================
Proposal Category: GO
Scientific Category: SOLAR SYSTEM
ID: 9745
Title: From molecules to aerosols: observing the haze creation
process during Titan's polar summer
PI: Mark Lemmon
PI Institution: Texas A & M Research Foundation
Our Cycle 11 observations of Titan at southern summer solstice reveal
unexpected complexity and an opportunity for science that has not previously
been possible. Titan currently has a polar hood below 65 degrees S. The polar
hood is dark in the visible relative to the southern mid-latitudes, as is
Titan's northern hemisphere. In the UV and near-IR, the hood is spectrally
distinct from the better-known north-south asymmetry, indicating a different
formation mechanism. The nature of the relation between the southern summer
hood and the northern spring equinox polar hood observed by Voyager is
uncertain. We propose a set of ultraviolet and supporting observations to
demonstrate the nature of temporal changes in the hood and to look for
expected stratospheric absorbing gasses. The gasses are precursors to Titan's
aerosols; the polar hood may be an early stage of aerosol evolution. Our
observations will provide important constraints on the chemistry and dynamics
of Titan's stratosphere at summer solstice. The chance to follow-up our
observations of the polar hood will allow us to assess the processes and
changes that are occurring now, so that Cassini observations of the polar
regions will not need to be interpreted in isolation from seasonal context.
================================================================================
Proposal Category: GO
Scientific Category: SOLAR SYSTEM
ID: 9746
Title: Binary systems in the Kuiper Belt
PI: Jean-Luc Margot
PI Institution: California Institute of Technology
The properties of the orbits of Kuiper belt object (KBO) satellites hold keys
to fundamental insight into masses and densities of KBOs, the interaction
history of the early solar system, the internal structure of distant ice-rock
bodies, and even the genesis of the Pluto-Charon binary. Within the past 18
months, 9 KBO satellite systems have been discovered, allowing for the first
time the possibility of characterizing a sample of KBO satellite orbital
properties. We propose HRC observations to determine satellite orbits in the 6
best cases. We have carefully devised a strategy for each of these 6 systems
to make maximum use of ground-based observations, previous HST observations,
and the smallest possible number of new HST observations. Our proposed
observations will efficiently provide highly reliable orbital solutions which
are critical to achieving the scientific promise available from the study of
these systems. Our strategy relies heavily on extensive Monte Carlo
simulations to define optimal times of observing such that each new point
obtained gives maximum leverage for refining the orbital solution. We find
that with this strategy we can provide mass solutions for all 6 systems to an
accuracy of better than 10\% using only 25 new HST observations. This highly
efficient program provides extreme scientific output with optimal use of
scarce resources.
================================================================================
Proposal Category: SNAP
Scientific Category: SOLAR SYSTEM
ID: 9747
Title: An Imaging Survey of the Statistical Frequency of
Binaries Among Exceptionally-Young Dynamical Families in
the Main Asteroid Belt
PI: William Merline
PI Institution: Southwest Research Institute
We propose an ambitious SNAPSHOT program to determine the frequency of
binaries among two very young asteroid families in the Main Belt, with
potentially profound implications. These families (of C- and S-type) have
recently been discovered (Nesvorny et al. 2002, Nature 417, 720), through
dynamical modeling, to have been formed at 5.8 MY and 8.3 MY ago in
catastrophic impact events. This is the first time such precise and young
ages have been assigned to a family. Main-belt binaries are almost certainly
produced by collisions, and we would expect a young family to have a
significantly higher frequency of binaries than the background, because they
may not yet have been destroyed by impact or longer-term gravitational
instabilities. In fact, one of the prime observables from such an event
should be the propensity for satellites. This is the best way that new
numerical models for binary production by collisions (motivated largely by our
ground-based discoveries of satellites among larger asteroids), can be
validated and calibrated. HST is the only facility that can be used to search
for binaries among such faint objects (V>17.5). We will also measure two
control clusters, one being an "old" family, and the other a collection of
background asteroids that do not have a family association, and further
compare with our determined value for the frequency of large main-belt
binaries (2%). We request visits to 180 targets, using ACS/HRC.
================================================================================
Proposal Category: GO
Scientific Category: SOLAR SYSTEM
ID: 9748
Title: Ceres: High-Resolution Mapping and Determination of
Physical Properties
PI: Joel Parker
PI Institution: Southwest Research Institute
We propose a modest, 6-orbit HST ACS/HRC program to fully map the asteroid 1
Ceres for the first time. These high signal-to-noise, high resolution maps
will be obtained in three ACS filter bandpasses from the visible to the UV.
The goals of our program are to advance knowledge about Ceres dramatically, to
resolve certain longstanding issues regarding Ceres, and to support planning
for the Dawn Discovery mission's planned orbital tour of Ceres. The specific
scientific objectives of this proposed Cycle 12 effort are: (1) To achieve
dense rotational phase coverage with multi-spectral imaging over the complete
rotation period of Ceres to map its surface; (2) To resolve surface features
and investigate the nature of the Piazzi feature detected by HST/FOC in 1995;
(3) To track surface features in order to unambigously determine Ceres' pole
position; (4) To measure the three-dimensional shape of Ceres better than any
existing shape model in order to significantly refine density measurements;
and (5) To map Ceres' color variegation and photometric parameters in order to
identify possible surface units for the first time. These goals require high
resolution visible and ultraviolet imaging, which can only be obtained with
HST. As we demonstrate in this proposal, the January, 2004 opposition of
Ceres is the best in the next 6 years for both data quality and planning of
the Dawn mission.
================================================================================
Proposal Category: GO
Scientific Category: COOL STARS
ID: 9749
Title: NICMOS Observations of the Gl 164 Companion
PI: Steven Pravdo
PI Institution: Jet Propulsion Laboratory
We propose to image an astrometrically-detected companion of Gl 164. The
companion was discovered with the Stellar Planet Survey (STEPS) instrument
operating on the Palomar 200" telescope. The mass of the companion is
estimated to be ~40 Jupiter masses or more placing it in the brown dwarf
range. If we can detect this companion with NICMOS and confirm its nature, we
will have one of the few direct measurements of the mass of a brown dwarf.
================================================================================
Proposal Category: GO
Scientific Category: STELLAR POPULATIONS
ID: 9750
Title: The Galactic Bulge Deep Field: A Planetary Transit
Survey and Very Deep Stellar Mass Function
PI: Kailash Sahu
PI Institution: Space Telescope Science Institute
We propose to observe a Galactic bulge field continuously with ACS/WFC over a
7-day period. We will monitor ~167,000 F, G, and K dwarfs down to V=23, in
order to detect transits by orbiting Jovian planets. If the frequency of "hot
Jupiters" is similar to that in the solar neighborhood, we will detect over
100 planets, more than doubling the number of extrasolar planets known. For
the brighter stars with transits, we will confirm the planetary nature of the
companions through radial-velocity measurements using the 8-m VLT. We will
determine the metallicities of most of the planet-bearing stars as well as a
control sample, through follow-up VLT spectroscopy. The metallicities of the
target stars range over more than 1.5 dex, allowing for a determination of the
dependence of planet frequency upon metallicity--a crucial element in
understanding planet formation. We will be able to discriminate between the
equally numerous disk and bulge stars via proper motions. Hence we will
determine, for the first time, the frequencies of planets in two entirely
different stellar populations. We will also determine for the first time the
distribution of planetary radii for extrasolar planets for both these
populations. Parallel observations with NICMOS will provide ultra-deep
near-infrared images of a nearby bulge field, which will be used to determine
the stellar luminosity and mass functions down to the brown-dwarf regime. The
data will also be useful for a variety of spinoff projects, including a census
of variable stars and of hot white dwarfs in the bulge, and the metallicity
distribution of bulge dwarfs.
================================================================================
Proposal Category: GO
Scientific Category: HOT Stars
ID: 9751
Title: Accurate Mass Determination of the Ancient White Dwarf
ER 8 Through Astrometric Microlensing
PI: Kailash Sahu
PI Institution: Space Telescope Science Institute
We propose to determine the mass of the very cool white dwarf ER 8 through
astrometric microlensing. We have predicted that ER 8 will pass very close
to a 15th-mag background star in January 2006, with an impact parameter of
less than 0.05 arcsec. As it passes in front, it will cause a deflection of
the background star's image by >8 milliarcsec, an amount easily detectable
with HST/FGS. The gravitational deflection angle depends only on the distances
and relative positions of the stars, and on the mass of the white dwarf. Since
the distances and positions can be determined precisely before the event, the
astrometric measurement offers a unique and direct method to measure the mass
of the white dwarf to high accuracy (<5%). Unlike all other stellar mass
determinations, this technique works for single stars (but only if they are
nearby and of sufficient mass). The mass of ER 8 is of special interest
because it is a member of the Galactic halo, and appears to be the oldest known
field white dwarf. This object can thus set a lower limit on the age of the Galactic
halo, but since white-dwarf cooling rates depend on their masses, the mass is a
necessary ingredient in the age determination. As a byproduct, we will obtain
an accurate parallax for ER 8, and thus its luminosity and (from its effective
temperature) its radius. Such quantities are at present rather poorly known for the
coolest white dwarfs, and will provide strong constraints on white-dwarf physics.
================================================================================
Proposal Category: GO
Scientific Category: STAR FORMATION
ID: 9752
Title: A Search for the Exciting Sources in OMC-1 through NICMOS
Polarization Measurements
PI: Janet Simpson
PI Institution: NASA Ames Research Center
Orion contains the site of the nearest region of massive star formation to the
Sun; only here can this pivotal process in galactic evolution be studied at
the highest resolution. There are 10^5 solar luminosities of radiation emitted
from the Orion Molecular Cloud (OMC-1), possibly from a young massive star or
protostar, or possibly from several, less luminous sources. Either way, the
powering source(s) in the closest site of massive star formation has still not
yet been identified. Here we propose to apply a new tool to determine which,
of several prospective sources, might prove to be the heart of OMC-1. The
sources cannot be seen directly because they lie in, or behind, a warm, dense
molecular cloud. However, their presence can be inferred in polarized light,
through the manner in which light is scattered off neighboring clouds.
Heretofore, the spatial resolution has not been adequate to identify the
locations of individual stars. We propose to use the NICMOS polarizers
combined with the high spatial resolution of HST to achieve this, in spite of
the high density of candidate objects in the core of Orion. The demands of
accurately measuring the polarization vectors of small, diffuse objects
relative to the surrounding background from dust-scattered light requires the
high Strehl ratio and stable point-spread function only achievable from space.
================================================================================
Proposal Category: GO
Scientific Category: GALAXIES
ID: 9753
Title: Morphologies of EROs and Field Galaxies in SIRTF's First
Look Survey: A Rich Early Release Dataset
PI: Lisa Storrie-Lombardi
PI Institution: California Institute of Technology
The SIRTF First Look Survey (FLS) will be the first scientific program
undertaken with NASA's next Great Observatory. The FLS provides the first
large sample of dusty galaxies to redshifts to z < 2 and a census of large-
scale global IR properties (luminosities, color temperatures, total dust mass,
etc.) HST observations to measure morphology are critical to provide insight
into the mechanisms which build up the various galaxy components--disks,
bulges as well as chaotic morphologies. We will measure quantitative
morphology of fifty extremely red objects (EROs) with targeted NICMOS
pointings and hundreds of field galaxies with ACS in parallel in the FLS. We
aim to understand how EROs fit into the evolutionary sequence of galaxy
formation. The combined HST and SIRTF observations will provide clues into the
physical processes responsible for generating powerful far-IR sources or,
conversely, may explain why some galaxies are inactive in the far-IR.
Ancillary ground-based optical, near-IR, and radio data have already been
obtained and DEIMOS spectra are scheduled for June, 2003. We waive the
proprietary period for the HST observations and if executed early in Cycle 12
the FLS will be the first complete SIRTF+HST survey made available to the
astronomical community, well in advance of the majority of the Legacy
observations and all of the GTO surveys.
================================================================================
Proposal Category: GO
Scientific Category: QUASAR ABSORPTION LINES AND IGM
ID: 9754
Title: Intergalactic O VI absorption at redshift <0.004
PI: Bart Wakker
PI Institution: University of Wisconsin - Madison
Simulations of the formation of large-scale structure in the universe predict
that at the present time a large fraction of the baryons in the intergalactic
medium (IGM) is in a warm/hot phase, with T=10^5-10^7 K. The warm phase has
been detected with HST in absorption through the OVI 1031.926, 1037.671
doublet at redshifts ~0.15-0.3. In a sample of 100 extra-galactic objects
observed with FUSE, we find 12 detections of OVI at redshifts z=0.0008-0.004
(v=250 to 1200 km/s). Many of these occur within 400 kpc and 50 km/s of a
nearby galaxy, making it much easier to understand the relation between the
OVI absorbers and galaxies. Our sample allows a comparison of the properties
of nearby vs more distant OVI absorbers. However, modeling the physical
conditions in the gas requires measurements of HI, OVI, CIV, NV and CIII. High
velocity resolution is required to resolve the HI, CIV and NV lines in order
to discriminate between collisional and photoionization. We propose to obtain
improved HI data, as well as the CIV and NV measurements for two absorbers at
z<0.004. One appears to represent collisional ionization (Mrk 876), while the
other probably represents a case of a photoionized system (Ton S180).
Understanding the ionization of the warm IGM is essential for determining
elemental abundance and the baryonic content of the gas.
================================================================================
Proposal Category: GO
Scientific Category: GALAXIES
ID: 9755
Title: Investigating the Powering Sources of Expanding
Supergiant Shells in the Nearby Dwarf Galaxy IC 2574
PI: Fabian Walter
PI Institution: National Radio Astronomy Observatory
Using the unique resolving capability of the Hubble Space Telescope (HST) and
the wide-field imaging capabilities of the ACS, we propose to perform a
stellar population study of two prominent supergiant shells (SGS) in the
nearby dwarf galaxy IC2574. By constructing the star formation history for
those SGSs we will for the first time be able to test if past star formation
created these impressive structures, as suggested by theory. We have carefully
selected 2 SGSs; one is young (age: few 10^7 yr, exhibiting a prominent
central stellar association) the other is older (few 10^8 yr), with no
obvious optical counterpart. The aim of this proposal is to determine the age
and SF history of the central stellar associations of both SGSs by B, V, and I
band imaging using HST's ACS. With only 4 oribits in total this is an exremely
efficient program. A primary goal is the comparison of the stellar ages with
the age estimates from the HI kinematics. Using color magnitude diagrams, we
will also estimate how many stars have evolved off the main sequence and
exploded as SN, giving an estimate for the total mechanical energy deposited.
A comparison with the values derived in other wavelengths is not only
important for understanding these particular SGSs but will also set strong
timing as well as energy constraints on the physical mechanisms which lie at
the origin of SGSs in general.
================================================================================
Proposal Category: GO
Scientific Category: HOT STARS
ID: 9756
Title: The Parallax of Geminga
PI: Frederick Walter
PI Institution: State University of New York at Stony Brook
The distances to neutron stars are a fundamental parameter that impacts
estimates of radii and luminosities, both of which have important
ramifications for neutron star heating and cooling and for the equation of
state of nuclear matter. A radius measured to 5% accuracy will provide useful
astrophysical constraints on the equation of matter at nuclear densities. This
requires an accurate measurment of the distance. Caraveo et al. have reported
a distance to the isolated pulsar Geminga based on three WFPC2 images. We have
not been able to reproduce that result. We request time with the ACS/WFC over
the next two years to obtain 4 images in order to determine the parallax of
Geminga. In addition to the general importance of understanding neutron star
radii and luminosities, this will provide specific insights into the history
of gamma ray pulsars in general, and of Geminga itself.
================================================================================
Proposal Category: GO
Scientific Category: ISM AND CIRCUMSTELLAR MATTER
ID: 9757
Title: Abundances, Dust, and Physical Conditions in the LMC ISM
PI: Daniel Welty
PI Institution: University of Chicago
STIS echelle spectra of the SMC star Sk 155 have revealed patterns of gas-
phase interstellar abundances (and corresponding depletions into dust) that
have not been seen in the Galactic ISM. In particular, Mg and Si (generally
thought to be major dust constituents) are essentially undepleted in the SMC
gas --- even for components with severe depletions of Fe and Ni. We propose
to obtain similar spectra of 3 LMC stars --- sampling different regions of
the LMC characterized by different UV extinction curves --- first to see
whether such "anomalous" abundances might also be present in the LMC (as
suggested by some FUSE spectra) and then to explore the relationships between
interstellar abundances, depletions, physical conditions, and dust properties
in environments characterized by low metallicity and moderately strong
radiation fields. These would be the first extensive UV spectra of any LMC
targets at resolutions better than 6 km/s. The analysis of these spectra will
have significant implications for (1) making models of interstellar dust
grains (which currently rely heavily on silicates); (2) understanding the
relationships between depletions, dust, and H_2 (which may be somewhat
different in the Milky Way, LMC, and SMC); (3) understanding the processes
affecting the ionization balance in diffuse interstellar clouds (e.g., charge
exchange with large molecules, cosmic-ray ionization); (4) testing theoretical
cloud models (which predict higher pressures in such environments); and (5)
interpreting the gas-phase abundances observed for QSO absorption-line systems
(which exhibit some similar properties).
================================================================================
Proposal Category: GO
Scientific Category: HOT STARS
ID: 9758
Title: Iron deficiency in hot hydrogen-deficient post-AGB stars
PI: Klaus Werner
PI Institution: Universitat Tubingen, Institut fur Astronomie &
Astrophysik
The first attempt to measure the iron abundance in hot hydrogen-deficient
post-AGB stars arrived at a surprising result. From the non-detection of iron
lines in FUSE spectra of three extremely hot (Teff>100,000K) PG1159-type
central stars of the planetary nebulae, we found that iron is deficient by at
least one order of magnitude. We propose HST/STIS observations of three
hydrogen-deficient post-AGB stars, each representing the UV-brightest member
of a spectroscopic subclass. High-resolution UV spectroscopy will reveal the
origin of the iron deficiency. The determination of the Fe/Ni abundance ratio
can decide if dust fractionation in the former AGB star atmosphere or s-
process neutron-capture in the interior helium-buffer layer is responsible for
the iron depletion. In the latter case we can verify our understanding of the
"born-again'' star phenomenon and of the s-process synthesis of trans-iron
elements in low-mass AGB stars.
================================================================================
Proposal Category: SNAP
Scientific Category: QUASAR ABSORPTION LINES AND IGM
ID: 9759
Title: Confirmation of New Candidates for the Study of
Intergalactic Helium
PI: Wei Zheng
PI Institution: Johns Hopkins University
The reionization of intergalactic helium is believed to take place between
redshift 3 and 4. The study of HeII Lyman-alpha absorption in four quasars at
2.71. Recently we have
identified large overdensities of red galaxies, strongly clustered around
powerful radio sources at z~1.5. We propose to image our two richest fields,
of Abell Class 0-1 richness, using the F814W and F606W filters on the ACS/WFC.
Our goals are to investigate: (1) Galaxy morphologies: we will determine the
bulge fractions of the red cluster galaxies, to confirm that they are early-
types, and measure their characteristic radii to investigate their
evolutionary status. (2) Colour gradients: we will search for colour gradients
indicative of recent star formation (particularly blue cores), or
inhomogeneities in the internal colours which might be indicative of recent
assembly. (3) Cluster membership: with two additional colours we will obtain
accurate photometric redshift estimates for all galaxies. Combined with
studies of nearby clusters and of field ellipticals, our results will place
very tight constraints on the formation of the most massive galaxies.
================================================================================
Proposal Category: SNAP
Scientific Category: GALAXIES
ID: 9765
Title: The Dusty ISM Substructure in Nearby Spiral Galaxies
PI: Roelof de Jong
PI Institution: Space Telescope Science Institute
We propose an ACS V&I imaging snapshot survey of all nearbe edge-on spiral
galaxies in order to measure the small scale structures in their dust
extinction down to the 10pc scale. Dust and molecular gas are thightly coupled
and therefore HST high resolution reddening maps can reveal information about
the cold ISM phase on a scale inaccessible from the groundby any other means.
We have recently discovered a sudden change in dust lane properties using
ground-based data; all galaxies with rotation speeds in access of 120km/s show
dust lanes, but none of the slower rotators does. This transition may be
caused by a sudden change in the state of the multiphase ISM, and HST
resolution imaging is needed to fully quantify this effect. Analysis will
consist of full radiative transfer modeling of dust extinction with realistic,
fractal like substructure and power spectrum analysis of the structure from
the global to the 10pc scale. By observing a sample of galaxies with a range
in structural parameters we can quantify how the cold ISM structure changes as
function of radius, rotation speed, local surface density, et cetera. This
information is duly needed with SIRTF soon providing a wealth of information
on dust absorbtion, but lacking the resolution to determine the small scale
distribution of the dust.
================================================================================
Proposal Category: GO
Scientific Category: GALAXIES
ID: 9766
Title: The Globular Cluster Systems of Spiral Galaxies along the
Hubble Sequence
PI: Duncan Forbes
PI Institution: Swinburne University of Technology
While the globular cluster (GC) systems of ellipticals and ongoing mergers
have been relatively well-studied with HST, very little is known about the GC
systems of spirals besides the Milky Way and M31. To constrain GC/galaxy
formation models, especially where spirals are the merger progenitors of
ellipticals, it is crucial to understand their GC properties. We propose to
obtain ACS images of three edge-on spirals, spanning the Hubble sequence, with
Keck spectroscopic follow-up. This will effectively double the number of well-
studied spiral systems. We will detect 100-200 GCs per galaxy, sufficient to
reveal GC subpopulations, their relative numbers, radial trends, and
dependences on Hubble type (e.g., a bulge vs. disk origin for red GCs). For
half of our GCs we will be able to measure individual sizes. HST is essential
for this project. By providing a much-needed comparative benchmark, these data
will allow researchers to better exploit the large existing HST database of
GCs in E/S0 galaxies.
================================================================================
Proposal Category: GO
Scientific Category: GALAXIES
ID: 9767
Title: Search for Black Holes in M31 Globular Clusters
PI: Karl Gebhardt
PI Institution: University of Texas at Austin
Whether globular clusters contain a central massive black hole remains a very
controversial subject today, and yet is extremely important for theoretical
models for black hole and cluster formation. Furthermore, the existence of
intermediate-mass black holes has important implications for supermassive
black hole and galactic bulge formation, as well as providing signatures in
gravitational wave detectors. We propose to obtain high spatial resolution,
long-slit spectroscopy of two globular clusters in M31, G78 and G280. These
two clusters represent the best ones in which to constrain a central black
hole. Most importantly, both of these clusters have long central relaxation
times, and thus confusion between a central black hole and a collection of
heavy stellar remnants is alleviated. We have considered all globular
clusters in our Galaxy and in M31; STIS observations of these two will
provide the strongest limits for a black hole in any cluster, and better than
the two claims made previously in the literature. Combined with the data for
G1, these three clusters have the three highest central velocity dispersions
for any cluster in the Local Group and will shed light on possible
connections between galaxy and globular cluster formation.
================================================================================
Proposal Category: GO
Scientific Category: ISM AND CIRCUMSTELLAR MATTER
ID: 9768
Title: Enabling Coronagraphic Polarimetry with NICMOS
PI: Dean Hines
PI Institution: Space Science Institute
We propose to enable a new mode on NICMOS that combines the powerful
diffracted light rejection of the coronagraph with the diagnostic power of
polarimetry. This new capability will open a new regime in high contrast
imaging that has not been possible before. We will enable this capability by
observing calibration targets with the coronagraph and the NIC2 polarizers in
place. The enabled science includes, but is not limited to, detection and
imaging of circumstellar debris in polarized light, the polarized emission
surrounding bright planetary nebulae, and the extended structure around bright
active galaxies. A similar capability is possible with the ACS, and therefore
HST would provide the only platform for this extremely high contrast imaging
covering the entire near-UV, optical and near-infrared wavelength regime.
Only the combined HST NICMOS system has the combined resolution and stability
(especially with the NCS) to provide high spatial resolution, coronagraphic,
near-infrared polarimetry in the foreseeable future. The technique is
absolutely unique to HST and will enable a new regime in high contrast
imaging.
================================================================================
Proposal Category: GO
Scientific Category: HOT STARS
ID: 9769
Title: STIS Observations of Orbital and Rotational Variations in
the Unique Post-Common Envelope System HS1136+6646
PI: Jay Holberg
PI Institution: University of Arizona
HS1136+6646 is a recently discovered close-binary system consisting of a hot
(Teff ~ 120,000 K) DAO white dwarf and a K7V main sequence companion. It is
unique in being a relatively bright, nearby example of both a very young post-
common envelope system and a pre-cataclysmic variable system. Although the K
star component of HS1136+6646 has now been well studied from the ground, the
white dwarf can only be effectively studied at UV wavelengths from space. We
propose extended STIS observations of HS1136+6646 which focus specifically on
the nature of the white dwarf, i.e., its mass, temperature, age, photospheric
composition and possible magnetic field. High-dispersion echelle spectra,
taken at quadrature of the 0.83607 day orbital period of the system will
provide an accurate determination of the gravitational redshift of the white
dwarf. A series of medium-echelle spectra will be used to test the hypothesis
that the low-amplitude modulations observed in the optical light curve are
associated with the rotation of the white dwarf.
================================================================================
Proposal Category: GO
Scientific Category: GALAXIES
ID: 9770
Title: Galaxy Evolution During Half the Age of the Universe: ACS
imaging of rich galaxy clusters
PI: Inger Jorgensen
PI Institution: Gemini Observatory, Northern Operations
Detailed studies of nearby galaxies (z<0.05) have shown that galaxies have
very complex histories of formation and evolution involving mergers, bursts of
star formation, and morphological changes. Even so, the global properties of
the galaxies (radii, luminosities, rotation velocities, velocity dispersions,
and absorption line strengths) follow a number of very tight (empirical)
scaling relations, e.g. the Tully-Fisher relation and the Fundamental Plane.
These relations place constraints on models for galaxy evolution. The results
for nearby galaxies rely on high signal-to-noise spectroscopy and multi-color
photometry. With the Gemini Telescopes and the Hubble Space Telescope (HST) it
is possible to carry out similar detailed studies of galaxies at much larger
redshifts, up to z~1.0, equivalent to half the age of the Universe. We have
started a project using the scaling relations and aimed at studying the galaxy
evolution over the last half of the age of the Universe. The project is based
on a large database of spectroscopy and photometry of galaxies in 15 X-ray
selected clusters of galaxies with redshifts between 0.15 and 1.0.
Spectroscopic observations are being obtained using both Gemini Telescopes; we
have observed 6 clusters so far, covering from z=0.18 to z=0.83. We propose to
use HST/ACS to image the clusters and determine the morphologies and measure
the sizes of the galaxies. At this time we ask for 26 orbits to image four of
the clusters in our sample.
================================================================================
Proposal Category: SNAP
Scientific Category: GALAXIES
ID: 9771
Title: The local Hubble flow and the density field within 6 Mpc
PI: Igor Karachentsev
PI Institution: Russian Academy of Sciences, Special Astrophysical Obs.
Great progress has been made recently in accurate distance measurements of
nearby galaxies beyond the Local Group based on the luminosity of the tip of
the red giant branch (TRGB). Over the last three years, snapshot surveys with
HST have provided us with the TRGB distances for more than a hundred nearby
galaxies obtained with an accuracy of about 10%. The local velocity field
within 5 Mpc exhibits a significant anisotropy which disagrees with a
spherical Virgo-centric flow. The local Hubble flow is very cold, with 1-D rms
deviations of ~30 km/s. Cosmological simulations with Cold Dark Matter can
only realize such low dispersions with a combination of a low mean density of
matter and a substantial component with negative pressure. There may be a
constraint on the equation of state w=-p/rho. Our observations will
concentrate on 116 galaxies whose expected distances lie within 4 - 6 Mpc,
allowing us to trace a Dark Matter distribution in the Local Volume with twice
the information currently available. The program is a good one for SNAP mode
because the order and rate that the observations are made are not very
important, as long as there is good completion over several years.
================================================================================
Proposal Category: GO
Scientific Category: COSMOLOGY
ID: 9772
Title: Galaxy Populations at Very Large Cluster Radii: The
Outskirts of MS1054-03 at z=0.83
PI: Daniel Kelson
PI Institution: Carnegie Institution of Washington
We propose to use the Advanced Camera for Surveys to image four selected
fields in the outskirts of the rich, X-ray luminous cluster MS1054-03 at
z=0.83. The high-resolution and sensitivity of ACS is required in order to
study the properties of the population of galaxies falling into the cluster
for the first time. By targeting regions of the cluster well beyond the virial
radius, we will: (1) study the transformation of infalling field spirals into
cluster early-types using, e.g., the morphology-density relation to large
radii and very low local densities; (2) determine the star-formation histories
of those field galaxies most recently accreted by the cluster, using accurate
colors, morphologies, bulge-to- disk ratios, bulge and disk scale lengths, M/L
ratios and line strengths; and (3) measure the frequency of galaxy-galaxy
mergers and interactions in the infall region. By combining wide-field HST/ACS
data with wide-field multi-object spectroscopy from the Magellan and Keck
telescopes, we can test the predictions made by galaxy formation models, study
how field spirals become early-type cluster members, and better constrain the
formation and evolution of galaxies in both clusters and the field.
================================================================================
Proposal Category: GO
Scientific Category: GALAXIES
ID: 9773
Title: Ram Pressure Stripping in the Virgo Spiral NGC 4522
PI: Jeffrey Kenney
PI Institution: Yale University
We propose to image in BVI with HST ACS the highly inclined Virgo cluster
spiral galaxy NGC 4522, which is perhaps the nearest and clearest case of a
galaxy whose interstellar medium (ISM) is being actively stripped by the
pressure of the intracluster medium (ICM). High resolution HST B-I mages of
dust in the ISM will show important details of the interaction, such as what
happens to giant molecular clouds in the interaction, how rapidly and cleanly
disks are stripped, and whether star formation is triggered by ICM pressure.
We will identify extraplanar star clusters which formed in the stripped gas,
and from their ages and spatial distribution constrain the stripping history
of NGC 4522. Only with the spatial resolution of HST can we map dust features
down to the few pc scale of GMCs, and clearly identify stars clusters. In-
depth study of this galaxy should provide new insight into the physical
processes which occur in ICM-ISM interactions, and give us greater
understanding of galaxy evolution in clusters of all types and at all
redshifts.
================================================================================
Proposal Category: GO
Scientific Category: GALAXIES
ID: 9774
Title: Young Massive Clusters in Spiral Galaxies and the
Connection with Open Clusters
PI: Soren Larsen
PI Institution: European Southern Observatory - Germany
We propose to carry out a census of star clusters in the disks of the nearby
spiral galaxies NGC 45, NGC 1313, NGC 4395, NGC 5236 and NGC 7793. Using ACS,
we will identify much fainter and older star clusters than possible in
previous ground-based surveys, or even in HST imaging of more distant
galaxies. For the first time, we will directly explore the connection between
young "massive'' (or "super'') star clusters (YMCs) and lower-mass "open''
clusters in different star forming environments. We will test the
universality of the luminosity- and mass functions of stellar clusters and
establish whether the presence of YMCs is a result of a top-heavy cluster
luminosity function, or follows from generally richer cluster systems. Our
target galaxies span a range of morphological properties, surface brightness
and star formation rate. Some of them are known from ground-based studies to
host large numbers of YMCs while others have more modest cluster
populations. However, previous ground-based data were restricted to luminous
clusters younger than about 500 Myr. Here we will extend the search to
clusters formed throughout the entire lifetime of each galaxy and reach
clusters with properties typical of the Milky Way open clusters. This will
allow us to close the gap between studies of extragalactic and Galactic disk
clusters.
================================================================================
Proposal Category: GO
Scientific Category: ISM AND CIRCUMSTELLAR MATTER
ID: 9775
Title: Tracking the Homunculus and Outer Ejecta of Eta Carinae
PI: Jon Morse
PI Institution: University of Colorado at Boulder
We request WFPC2 images of Eta Carinae in order to complete our WFPC2 database
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 to 8 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 to better than 15 km/s precision and should
be able to discern deviations from linear motions that are predicted in some
models for the Giant Eruption. 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. We 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. The
science goals and exposures requested here are NOT covered in the Cycle 11
Treasury program to monitor the Eta Carinae ''event'' in May 2003.
================================================================================
Proposal Category: GO
Scientific Category: GALAXIES
ID: 9776
Title: Black Holes in Big Galaxies with Small Bulges
PI: Douglas Richstone
PI Institution: University of Michigan
In early-type galaxies the black hole (BH) mass is tightly correlated with the
bulge velocity dispersion. This correlation suggests that the BH mass is
determined by local processes in the central part of the galaxy. However, the
bulge dispersion in these galaxies is correlated with the disk circular speed
which in turn correlates with the inferred halo circular speed (the "disk-halo
conspiracy"). For this reason, existing data cannot decide whether the BH
mass is set by the bulge dispersion or the disk or halo circular speed. We
propose to break this degeneracy by weighing the BH in 3 Sc galaxies in which
the ratio of bulge circular speed to bulge velocity dispersion is large,
leading to large differences between BH masses predicted from these
quantities. These measurements will increase the number of carefully studied
Sc bulges from one to four and will determine whether the masses of nuclear
BHs are set by (presumably baryonic) processes in galaxy bulges or by
(presumably non-baryonic) processes in their dark halos.
================================================================================
Proposal Category: GO
Scientific Category: COSMOLOGY
ID: 9777
Title: The environment of QSOs at the reionization epoch
PI: Massimo Stiavelli
PI Institution: Space Telescope Science Institute
Our goal is to elucidate the role of QSOs and galaxies at the tail end of
reionization by identifying z~6 galaxies near SDSS z>6 QSOs through their red
i-z colors. A similar technique was used by the SDSS to identify the QSOs
themselves. Based on our understanding of the growth of structure in the
Universe and on observations at z ~= 4, we expect z~6 QSOs to be associated to
the high peaks in the matter density distribution. Therefore, they should be
surrounded by an excess of objects - as compared to random fields - unless the
ionizing radiation from the QSOs themselves is inhibiting star formation. We
will concentrate on 5 QSOs discovered by the SDSS at z>~6 and spend 7 orbits
with ACS on each of the QSO fields (2.5 in F775W - i - and 4.5 in F850LP -
z), for a total of 35 orbits. The exposures are optimized for the detection of
objects with i-z> 2. The reference properties of the field population will be
provided by GOODS which is reaching the same depth. The proposed observations
will be capable of revealing the dominant effect between galaxy suppression by
the QSO ionizing flux and number density excess due to clustering. We will
test whether the balance between suppression and enhancement evolves with
redshift. We will also be able to estimate for these fields the ionizing
continuum contribution by galaxies and compare it with that of the QSOs. If
galaxies are found to be comparably important to QSOs in these selected
fields, the idea that hydrogen reionization is primarily due to stellar
radiation would be significantly strengthened.
================================================================================
Proposal Category: GO
Scientific Category: ISM AND CIRCUMSTELLAR MATTER
ID: 9778
Title: Probing Outflowing Winds from the Galactic Center
PI: John Stocke
PI Institution: University of Colorado at Boulder
We propose to use two extragalactic sightlines to probe our own Galaxy's
"starburst" wind emanating from the Galactic Center. While new infrared
imaging and spectroscopy have detected massive stars and very recent (<3x10^6
yrs) star formation in the Galactic Center region, only indirect evidence
(e.g., radio loops and arcs, bi-conical cavity edges seen in the mid-IR)
exists for a wind. However, these winds are routinely detected from starbursts
in other galaxies. Far-UV STIS echelle spectroscopy (E140M) of two targets on
either side of the Galactic Center at (l,b)=(350,-33) and (349,55) will allow
us to map the kinematics of outflowing gas in high ionization species of N V,
Si IV and C IV. Similar spectra of distant (1.5-5 kpc), bright B stars in the
same regions of the sky will allow us to remove foreground contaminating
components due to the Sco-Cen OB associations. Lower resolution STIS first-
order and FUSE spectra show highly redshifted gas in N V and O VI respectively
along these sightlines; these new observations will provide three times better
spectral resolution (7-10 km/s in the 1185-1580A region) so that the kinematic
signature of the outflow can definitely be detected. The foreground stars will
allow us to determine whether the outflow is from the Galactic Center or the
Sco-Cen OB associations. Absorption line column densities will be used to
estimate the outflowing mass and energy by assuming a metallicity and ionizing
source for the gas.
================================================================================
Proposal Category: GO
Scientific Category: COSMOLOGY
ID: 9779
Title: Giant Lya Halos Around High Redshift Radio Galaxies
PI: Wil van Breugel
PI Institution: Lawrence Livermore National Laboratory
We propose to use the ACS + ramp filter to image the morphologies of several
high redshift, giant Lya emission line halos associated with radio galaxies.
High redshift radio galaxies are the likely precursors of the most massive
elliptical galaxies known today. There is increasing evidence that they are
forming in the centers of giant halos in overdense galaxy regions or
`protoclusters'. The halos provide a unique diagnostic to study the formation
of these massive galaxies and determine the importance of AGN/starburst
feedback during this process. The capability of HST to resolve fine detail is
essential for the interpretation of their complex morphologies. Our targets
have also a number of Lya excess galaxies near the halos which fall within the
field-of-view of the ACS + ramp filters. Our images will resolve these systems
and we will investigate whether there is morphological evidence for starburst
outflows. Starburst winds have been proposed as a source of heat and chemical
enrichment for protoclusters, which may significantly affect their evolution.
================================================================================
Proposal Category: GO
Scientific Category: COSMOLOGY
ID: 9780
Title: NIC3 Imaging of z~6 Candidates in a Deep ACS Parallel
Field: Finding the reionizing population and their LF
PI: Haojing Yan
PI Institution: Arizona State University
A fundamental cosmological question is when and how the universe was
reionized. It is now generally believed that the reionization ended by z=6.
There is evidence that QSO/AGN cannot provide enough photons to keep the
universe ionized at that epoch. In Yan et al. (2003), we presented a first
statistically significant sample of 6.0