HUBBLE SPACE TELESCOPE - Continuing to collect World Class
Science
DAILY REPORT #4676
PERIOD COVERED: 5am August 15 - 5am August 18, 2008 (DOY
228/0900z-231/0900z)
OBSERVATIONS SCHEDULED
NIC1/NIC2/NIC3 8795
NICMOS Post-SAA Calibration - CR Persistence Part 6
A new procedure proposed to alleviate the CR-persistence
problem of
NICMOS. Dark frames will be obtained immediately upon
exiting the SAA
contour 23, and every time a NICMOS exposure is scheduled
within 50
minutes of coming out of the SAA. The darks will be
obtained in parallel
in all three NICMOS Cameras. The POST-SAA darks will be
non-standard
reference files available to users with a USEAFTER
date/time mark. The
keyword 'USEAFTER=date/time' will also be added to the
header of each
POST-SAA DARK frame. The keyword must be populated with
the time, in
addition to the date, because HST crosses the SAA ~8 times
per day so
each POST-SAA DARK will need to have the appropriate time
specified, for
users to identify the ones they need. Both the raw and
processed images
will be archived as POST-SAA DARKSs. Generally we expect
that all NICMOS
science/calibration observations started within 50 minutes
of leaving an
SAA will need such maps to remove the CR persistence from
the science i
mages. Each observation will need its own CRMAP, as
different SAA
passages leave different imprints on the NICMOS detectors.
NIC2 11548
NICMOS Imaging of Protostars in the Orion A Cloud: The
Role of
Environment in Star Formation
We propose NICMOS observations of a sample of 252
protostars identified
in the Orion A cloud with the Spitzer Space Telescope.
These
observations will image the scattered light escaping the
protostellar
envelopes, providing information on the shapes of outflow
cavities, the
inclinations of the protostars, and the overall
morphologies of the
envelopes. In addition, we ask for Spitzer time to obtain
55-95 micron
spectra of 75 of the protostars. Combining these new data
with existing
3.6 to 70 micron photometry and forthcoming 5-40 micron
spectra measured
with the Spitzer Space Telescope, we will determine the
physical
properties of the protostars such as envelope density,
luminosity,
infall rate, and outflow cavity opening angle. By
examining how these
properties vary with stellar density (i.e. clusters vs
groups vs
isolation) and the properties of the surrounding molecular
cloud; we can
directly measure how the surrounding environment
influences protostellar
evolution, and consequently, the formation of stars and
planetary
systems. Ultimately, this data will guide the development
of a theory of
protostellar evolution.
WFPC2 11544
The Dynamical Legacy of Star Formation
We propose to use WFPC2 to conduct a wide-field imaging
survey of the
young cluster IC348. This program, in combination with
archival HST
observations, will allow us to measure precise proper
motions for
individual cluster members, characterizing the
intra-cluster velocity
dispersion and directly studying the dynamical signatures
of star
formation and early cluster evolution. Our projected
astrometric
precision (~1 mas in each epoch) will allow us to
calculate individual
stellar velocities to unprecedented precision (<0.5
mas/yr; <1 km/s) and
directly relate these velocities to observed spatial
substructure within
the cluster. This survey will also allow us to probe
small-scale star
formation physics by searching for high-velocity stars
ejected from
decaying multiple systems, expanding our knowledge of
multiplicity in
dense environments, and identifying new substellar and
planetary-mass
cluster members based on kinematic membership tests.
NIC1/NIC2/NIC3 11330
NICMOS Cycle 16 Extended Dark
This takes a series of Darks in parallel to other
instruments.
WFPC2 11316
HST Cycle 16 & Pre-SM4 Optical Monitor
This is a continuation of the Cycle 15 & pre-SM4
Optical Monitor, 11020.
Please see that proposal for a more complete description
of the
observing strategy. The 6 visits comprising this proposal
observe two
single standard stars with WFPC2/PC in order to establish
overall OTA
focal length for the purposes of focus maintenance. The
goal of this
monitoring before SM4 is to establish a best estimate of
the OTA focus
entering SMOV.
ACS/SBC/WFPC2 11230
HST FUV Observations of Brightest Cluster Galaxies: The
Role of Star
Formation in Cooling Flows and BCG Evolution
The intracluster medium (ICM) now appears to be a very
dynamic place
where heating and cooling processes vie for dominance and
an uneasy
equilibrium is maintained. Since these same processes may
operate during
the process of galaxy formation, the centers of clusters
of galaxies
provide low redshift laboratories for studying the
critical processes
involved in galaxy formation and black hole growth. At the
present time,
the main questions are (1) How much gas is cooling out of
the ICM? (2)
How much star formation is ongoing? (3) What is the impact
of the gas
and star formation on the central BCG? In order to measure
the current
star formation in BCGs we have undertaken a program of
Spitzer IRAC and
MIPS observations. We are in process of obtaining
observations of a
sample of Brightest Cluster Galaxies in 70 clusters
selected from the
ROSAT all sky survey. In about 25% of the sources observed
so far, we
detect a mid-IR excess which we attribute to dust heated
by star
formation. We propose to obtain ACS/SBC observations of
the Lyman Alpha
emission line and the adjacent FUV continuum in 7 BCGs
which are in
cooling core clusters of galaxies and have a large mid-IR
excess. We
also propose WFPC2 F606W observations of the two clusters
without high
resolution imaging to allow us to image the dust on the
same scale as
the Far UV continuum. The FUV will allow us to confirm the
presence of
ongoing star formation in these BCGs and will allow us to
rule out an
AGN as the dominant contributor to the mid-IR. The
morphology and
spatial extent of the young stars and the heated dust and
CO will
constrain the spatial scale over which star formation
occurs and thus
where the cooling gas is deposited. The combination of our
FUV and IR
observations will allow us to estimate the star formation
rates which
must balance the rate at which cold gas is deposited in
the BCG. Our
proposed FUV observations will produce unique information
about the
cooling gas, the true mass accretion rates, and the star
formation rates
in BCGs and its effect on the galaxy.
NIC2 11208
The Co-evolution of Spheroids and Black Holes in the Last
Six Billion
Years
The masses of giant black holes are correlated with the
luminosities,
masses, and velocity dispersions of the bulges of their
host galaxies.
This empirical correlation of phenomena on widely
different scales {from
pcs to kpcs} suggests that the formation and evolution of
galaxies and
central black holes are closely linked. In Cycle 13, we
have started a
campaign to map directly the co-evolution of spheroids and
black-holes
by measuring in observationally favorable redshift windows
the empirical
correlations connecting their properties. By focusing on
Seyfert 1s,
where the nucleus and the stars contribute comparable
fractions of total
light, black hole mass and bulge dispersion are obtained
from Keck
spectroscopy. HST is required for accurate measurement of
the non
stellar AGN continuum, the morphology of the galaxy, and
the structural
parameters of the bulge. The results at z=0.36 indicate a
surprisingly
fast evolution of bulges in the past 4 Gyrs {significant
at the 95%CL},
in the sense that bulges were significantly smaller for a
given black
hole mass. Also, the large fraction of mergers and
disturbed galaxies
{4+2 out of 20} identifies gas-rich mergers as the mechanisms
responsible for bulge-growth. Going to higher redshift --
where
evolutionary trends should be stronger -- is needed to
confirm these
tantalizing results. We propose therefore to push our
investigation to
the next suitable redshift window z=0.57 {lookback-time 6
Gyrs}. Fifteen
objects are the minimum number required to map the
evolution of the
empirical correlations between bulge properties and
black-hole mass, and
to achieve a conclusive detection of evolution
{>99%CL}.
WFPC2 11206
At the Cradle of the Milky Way: Formation of the Most
Massive Field Disk
Galaxies at z>1
We propose to obtain 2 orbit WFPC2 F814W images of a
sample of the 15
most massive galaxies found at $1 < z < 1.3$. These
were culled from
over 20,000 Keck spectra collected as part of DEEP and are
unique among
high redshift massive galaxy samples in being
kinematically selected.
Through a recent HST NICMOS-2 imaging program {GO-10532},
we have
confirmed that these galaxies have regular stellar disks,
and their
emission line kinematics are not due to gradients from
merging
components. These potentially very young galaxies are
likely precursors
to massive local disks, assuming no further merging. The
proposed WFPC2
and existing NIC-2 data provide colors, stellar masses,
and ages of
bulge and disk subcomponents, to assess whether old
stellar bulges and
disks are in place at that time or still being built, and
constrain
their formation epochs. Finally, this sample will yield
the first
statistically significant results on the $z > 1$ evolution
of the
size-velocity-luminosity scaling relations, for massive
galaxies at
different wavelengths, and constrain whether this
evolution reflects
stellar mass growth, or passive evolution, of either bulge
or disk
components.
NIC1 11205
The Effects of Multiplicity on the Evolution of Young
Stellar Objects: A
NICMOS Imaging Study
We propose to use NICMOS to investigate the multiplicity
of young
stellar objects (YSOs) in the Orion B molecular cloud.
Previous
observations with the Spitzer Space Telescope have
revealed a remarkable
star forming filament near the NGC 2068 reflection nebula.
The
population of YSOs associated with the filament exhibit a
surprisingly
wide range of circumstellar evolutionary states, from
deeply embedded
protostars to T Tauri accretion disks. Many of the
circumstellar disks
themselves show evidence for significant dust evolution,
including grain
growth and settling and cleared inner holes, apparently in
spite of the
very young age of these stars. We will estimate the binary
fraction of a
representative sample of objects in these various stages
of evolution in
order to test whether companions may play a significant
role in that
evolution.
WFPC2 11203
A Search for Circumstellar Disks and Planetary-Mass
Companions around
Brown Dwarfs in Taurus
During a 1-orbit program in Cycle 14, we used WFPC2 to
obtain the first
direct image of a circumstellar disk around a brown dwarf.
These data
have provided fundamental new constraints on the formation
process of
brown dwarfs and the properties of their disks. To search
for additional
direct detections of disks around brown dwarfs and to
search for
planetary-mass companions to these objects, we propose a
WFPC2 survey of
32 brown dwarfs in the Taurus star-forming region.
WFPC2 11202
The Structure of Early-type Galaxies: 0.1-100 Effective
Radii
The structure, formation and evolution of early-type
galaxies is still
largely an open problem in cosmology: how does the
Universe evolve from
large linear scales dominated by dark matter to the highly
non-linear
scales of galaxies, where baryons and dark matter both
play important,
interacting, roles? To understand the complex physical
processes
involved in their formation scenario, and why they have
the tight
scaling relations that we observe today {e.g. the
Fundamental Plane}, it
is critically important not only to understand their
stellar structure,
but also their dark-matter distribution from the smallest
to the largest
scales. Over the last three years the SLACS collaboration
has developed
a toolbox to tackle these issues in a unique and
encompassing way by
combining new non-parametric strong lensing techniques,
stellar
dynamics, and most recently weak gravitational lensing,
with
high-quality Hubble Space Telescope imaging and VLT/Keck
spectroscopic
data of early-type lens systems. This allows us to break
degeneracies
that are inherent to each of these techniques separately
and probe the
mass structure of early-type galaxies from 0.1 to 100
effective radii.
The large dynamic range to which lensing is sensitive
allows us both to
probe the clumpy substructure of these galaxies, as well
as their
low-density outer haloes. These methods have convincingly
been
demonstrated, by our team, using smaller pilot-samples of
SLACS lens
systems with HST data. In this proposal, we request
observing time with
WFPC2 and NICMOS to observe 53 strong lens systems from
SLACS, to obtain
complete multi-color imaging for each system. This would
bring the total
number of SLACS lens systems to 87 with completed HST
imaging and
effectively doubles the known number of galaxy-scale
strong lenses. The
deep HST images enable us to fully exploit our new
techniques, beat down
low-number statistics, and probe the structure and
evolution of early-
type galaxies, not only with a uniform data-set an order
of magnitude
larger than what is available now, but also with a fully
coherent and
self-consistent methodological approach!
WEPC2 11196
An Ultraviolet Survey of Luminous Infrared Galaxies in the
Local
Universe
At luminosities above 10^11.4 L_sun, the space density of
far-infrared
selected galaxies exceeds that of optically selected
galaxies. These
Luminous Infrared Galaxies {LIRGs} are primarily
interacting or merging
disk galaxies undergoing starbursts and creating/fueling
central AGN. We
propose far {ACS/SBC/F140LP} and near {WFPC2/PC/F218W} UV
imaging of a
sample of 27 galaxies drawn from the complete IRAS Revised
Bright Galaxy
Sample {RBGS} LIRGs sample and known, from our Cycle 14 B
and I-band ACS
imaging observations, to have significant numbers of
bright {23 < B < 21
mag} star clusters in the central 30 arcsec. The HST UV
data will be
combined with previously obtained HST, Spitzer, and GALEX
images to {i}
calculate the ages of the clusters as function of merger
stage, {ii}
measure the amount of UV light in massive star clusters
relative to
diffuse regions of star formation, {iii} assess the
feasibility of using
the UV slope to predict the far-IR luminosity {and thus
the star
formation rate} both among and within IR-luminous
galaxies, and {iv}
provide a much needed catalog of rest- frame UV
morphologies for
comparison with rest-frame UV images of high-z LIRGs and
Lyman Break
Galaxies. These observations will achieve the resolution
required to
perform both detailed photometry of compact structures and
spatial
correlations between UV and redder wavelengths for a
physical
interpretation our IRX-Beta results. The HST UV data,
combined with the
HST ACS, Spitzer, Chandra, and GALEX observations of this
sample, will
result in the most comprehensive study of luminous
starburst galaxies to
date.
ACS/SBC WFPC2 11175
UV Imaging to Determine the Location of Residual Star
Formation in
Galaxies Recently Arrived on the Red Sequence
We have identified a sample of low-redshift {z = 0.04 -
0.10} galaxies
that are candidates for recent arrival on the red
sequence. They have
red optical colors indicative of old stellar populations,
but blue
UV-optical colors that could indicate the presence of a
small quantity
of continuing or very recent star formation. However,
their spectra lack
the emission lines that characterize star-forming
galaxies. We propose
to use ACS/SBC to obtain high-resolution imaging of the UV
flux in these
galaxies, in order to determine the spatial distribution
of the last
episode of star formation. WFPC2 imaging will provide B,
V, and I
photometry to measure the main stellar light distribution
of the galaxy
for comparison with the UV imaging, as well as to measure
color
gradients and the distribution of interstellar dust. This
detailed
morphological information will allow us to investigate the
hypothesis
that these galaxies have recently stopped forming stars
and to compare
the observed distribution of the last star formation with
predictions
for several different mechanisms that may quench star
formation in
galaxies.
NIC1/NIC2 11172
Defining Classes of Long Period Variable Stars in M31
We propose a thrifty but information-packed investigation
{1440
exposures total} with NICMOS F205W, F160W and F110W
providing crucial
information about Long Period Variables in M31, at a level
of detail
that has recently allowed the discovery of new variable
star classes in
the Magellanic Clouds, a very different stellar
population. These
observations are buttressed by an extensive map of the
same fields with
ACS and WFPC2 exposures in F555W and F814W, and a massive
ground-based
imaging patrol producing well-sampled light curves for
more than 400,000
variable stars. Our primary goal is to collect sufficient
NIR data in
order to analyze and classify the huge number of
long-period variables
in our catalog {see below} through Period-Luminosity {P/L}
diagrams. We
will produce accurate P/L diagrams for both the bulge and
a progression
of locations throughout the disk of M31. These diagrams
will be similar
in quality to those currently in the Magellanic Clouds,
with their lower
metallicity, radically different star formation history,
and larger
spread in distance to the variables. M31 offers an
excellent chance to
study more typical disk populations, in a manner which
might be extended
to more distant galaxies where such variables are still
visible, probing
a much more evenly spread progenitor age distribution than
cepheids {and
perhaps useful as a distance scale alternative or
cross-check}. Our data
will also provide a massive and unique color-magnitude
dataset, and
allow us to confirm the microlensing nature of a large
sample of
candidate lensed sources in M31. We expect that this study
will produce
several important results, among them a better
understanding of P/L and
P/L-color relations for pulsating variables which are
essential to the
extragalactic distance ladder, will view these variables
at a common
distance over a range of metallicities {eliminating the
distance- error
vs. metallicity ambiguity between the LMC and SMC}, allow
further
insight into possible faint-variable mass-loss for higher
metallicities,
and in general produce a sample more typical of giant disk
galaxies
predominant in many studies.
ACS/SBC 11158
HST Imaging of UV emission in Quiescent Early-type
Galaxies
We have constructed a sample of early type galaxies at
z~0.1 that have
blue UV-optical colors, yet also show no signs of optical
emission, or
extended blue light. We have cross-correlated the SDSS
catalog and the
Galaxy Evolution Explorer Medium Imaging Survey to select
a sample of
galaxies where this UV emission is strongest. The origin
of the UV
rising flux in these galaxies continues to be debated, and
the
possibility that some fraction of these galaxies may be
experiencing low
levels of star formation cannot be excluded. There is also
a possibility
that low level AGN activity {as evidenced by a point
source} is
responsible We propose to image the UV emission using the
HST/SBC and to
explore the morphology of the UV emission relative to the
optical light.
NIC2 11157
NICMOS Imaging Survey of Dusty Debris Around Nearby Stars
Across the
Stellar Mass Spectrum
Association of planetary systems with dusty debris disks
is now quite
secure, and advances in our understanding of planet
formation and
evolution can be achieved by the identification and
characterization of
an ensemble of debris disks orbiting a range of central
stars with
different masses and ages. Imaging debris disks in
starlight scattered
by dust grains remains technically challenging so that
only about a
dozen systems have thus far been imaged. A further advance
in this field
needs an increased number of imaged debris disks. However,
the technical
challenge of such observations, even with the superb
combination of HST
and NICMOS, requires the best targets. Recent HST imaging
investigations
of debris disks were sample-limited not limited by the
technology used.
We performed a search for debris disks from a
IRAS/Hipparcos cross
correlation which involved an exhaustive background
contamination check
to weed out false excess stars. Out of ~140 identified
debris disks, we
selected 22 best targets in terms of dust optical depth
and disk angular
size. Our target sample represents the best currently
available target
set in terms of both disk brightness and resolvability.
For example, our
targets have higher dust optical depth, in general, than
newly
identified Spitzer disks. Also, our targets cover a wider
range of
central star ages and masses than previous debris disk
surveys. This
will help us to investigate planetary system formation and
evolution
across the stellar mass spectrum. The technical
feasibility of this
program in two-gyro mode guiding has been proven with
on-orbit
calibration and science observations during HST cycles 13,
14, and 15.
ACS/SBC 11151
Evaluating the Role of Photoevaporation of Protoplanetary
Disk Dispersal
Emission produced by accretion onto the central star leads
to
photoevaporation, which may play a fundamental role in
disk dispersal.
Models of disk photoevaporation by the central star are
challenged by
two potential problems: the emission produced by accretion
will be
substantially weaker for low-mass stars, and
photoevaporation must
continue as accretion slows. Existing FUV spectra of CTTSs
are biased to
solar-mass stars with high accretion rates, and are
therefore
insufficient to address these problems. We propose use
HST/ACS SBC
PR130L to obtain FUV spectra of WTTSs and of CTTSs at low
masses and
mass accretion rates to provide crucial data to evaluate
photoevaporation models. We will estimate the FUV and EUV
luminosities
of low-mass CTTSs with small mass accretion rates, CTTSs
with transition
disks and slowed accretion, and of magnetically-active
WTTSs.
WFPC2/NIC3/ACS/SBC 11144
Building on the Significant NICMOS Investment in GOODS: A
Bright,
Wide-Area Search for z>=7 Galaxies
One of the most exciting frontiers in observational
cosmology has been
to trace the buildup and evolution of galaxies from very
early times.
While hierarchical theory teaches us that the star
formation rate in
galaxies likely starts out small and builds up gradually,
only recently
has it been possible to see evidence for this
observationally through
the evolution of the LF from z~6 to z~3. Establishing that
this build up
occurs from even earlier times {z~7-8} has been difficult,
however, due
to the small size of current high-redshift z~7-8 samples
-- now
numbering in the range of ~4-10 sources. Expanding the
size of these
samples is absolutely essential, if we are to push current
studies of
galaxy buildup back to even earlier times. Fortunately, we
should soon
be able to do so, thanks to ~50 arcmin**2 of deep {26.9 AB
mag at 5
sigma} NICMOS 1.6 micron data that will be available over
the two ACS
GOODS fields as a result of one recent 180-orbit ACS
backup program and
a smaller program. These data will nearly triple the deep
near-IR
imaging currently available and represent a significant
resource for
finding and characterizing the brightest high-redshift
sources -- since
high-redshift candidates can be easily identified in these
data from
their red z-H colours. Unfortunately, the red z-H colours
of these
candidates are not sufficient to determine that these
sources are at
z>=7, and it is important also to have deep photometry
at 1.1 microns.
To obtain this crucial information, we propose to follow
up each of
these z-H dropouts with NICMOS at 1.1 microns to determine
which are at
high redshift and thus significantly expand our sample of
luminous, z>=7
galaxies. Since preliminary studies indicate that these
candidates occur
in only 30% of the NIC3 fields, our follow-up strategy is
~3 times as
efficient as without this preselection and 9 times as
efficient as a
search in a field with no pre- existing data. In total, we
expect to
identify ~8 luminous z-dropouts and possibly ~2 z~10 J-
dropouts as a
result of this program, more than tripling the number
currently known.
The increased sample sizes are important if we are to
solidify current
conclusions about galaxy buildup and the evolution of the
LF from z~8.
In addition to the high redshift science, these deep 1.1
micron data
would have significant value for many diverse endeavors,
including {1}
improving our constraints on the stellar mass density at
z~7-10 and {2}
doubling the number of galaxies at z~6 for which we can
estimate dust
obscuration.
WFPC2 11129
The Star Formation History of the Fornax Dwarf Spheroidal
Galaxy
The Fornax dwarf spheroidal galaxy is one of the most
luminous dwarf
satellites of the Milky Way. It is unusual in many ways:
it hosts 5
globular clusters, shows some relatively young stars, and
has faint
sub-structures which have been interpreted as signs of
recent
interactions. It is thus of great interest to learn the
complete star
formation history {SFH} of Fornax to establish a link
between its
evolutionary path and the predictions from numerical
simulations, as a
test of our understanding of dwarf galaxy evolution. Yet
many questions
remain open. Is the old stellar population made up of
stars formed in a
very early burst, perhaps before the epoch of
re-ionization, or the
result of a more continuous star formation between 13 and
9 Gyr ago ?
How quickly did Fornax increase its metallicity during its
initial
assembly and during subsequent episodes of star formation
? Are
accretion episodes required to explain the age-metallicity
history of
Fornax ? However, there has never been a comprehensive
study of the
global SFH of the Fornax field based on data of sufficient
depth to
unambiguously measure the age mixture of the stellar
populations and
their spatial variation. We propose to use the WFPC2 to
obtain very deep
images in several fields across the central region of
Fornax in order to
reach the oldest main-sequence turnoffs. The number of
fields is
determined by the need to measure the SFH over different regions
with
distinct kinematics and metallicity. The resolution
achievable with HST
is crucial to answer these questions because, to derive
the age
distribution of the oldest stars, we are interested in I
magnitude
differences of the order 0.2 mag in crowded fields at
V=24.5. We will
directly measure the time variation in star-formation rate
over the
entire galaxy history, from first stars coeval with the
Milky Way halo
to the youngest populations 200 Myr ago. The combination
of detailed CMD
analysis with WFPC2 with our existing metallicity and
kinematic
information will allow us to trace out the early phases of
its
evolution.
NIC3 11107
Imaging of Local Lyman Break Galaxy Analogs: New Clues to
Galaxy
Formation in the Early Universe
We have used the ultraviolet all-sky imaging survey
currently being
conducted by the Galaxy Evolution Explorer {GALEX} to
identify for the
first time a rare population of low-redshift starbursts
with properties
remarkably similar to high-redshift Lyman Break Galaxies
{LBGs}. These
"compact UV luminous galaxies" {UVLGs} resemble
LBGs in terms of size,
SFR, surface brightness, mass, metallicity, kinematics,
dust, and color.
The UVLG sample offers the unique opportunity of
investigating some very
important properties of LBGs that have remained virtually
inaccessible
at high redshift: their morphology and the mechanism that
drives their
star formation. Therefore, in Cycle 15 we have imaged 7
UVLGs using ACS
in order to 1} characterize their morphology and look for
signs of
interactions and mergers, and 2} probe their star
formation histories
over a variety of timescales. The images show a striking
trend of small-
scale mergers turning large amounts of gas into vigorous
starbursts {a
process referred to as dissipational or "wet"
merging}. Here, we propose
to complete our sample of 31 LBG analogs using the ACS/SBC
F150LP {FUV}
and WFPC2 F606W {R} filters in order to create a
statistical sample to
study the mechanism that triggers star formation in UVLGs
and its
implications for the nature of LBGs. Specifically, we will
1} study the
trend between galaxy merging and SFR in UVLGs, 2}
artificially redshift
the FUV images to z=1-4 and compare morphologies with
those in similarly
sized samples of LBGs at the same rest-frame wavelengths
in e.g. GOODS,
UDF, and COSMOS, 3} determine the presence and morphology
of significant
stellar mass in "pre-burst" stars, and 4} study
their immediate
environment. Together with our Spitzer {IRAC+MIPS}, GALEX,
SDSS and
radio data, the HST observations will form a unique union
of data that
may for the first time shed light on how the earliest
major episodes of
star formation in high redshift galaxies came about. This
proposal was
adapted from an ACS HRC+WFC proposal to meet the new Cycle
16 observing
constraints, and can be carried out using the ACS/SBC and
WFPC2 without
compromising our original science goals.
NIC2 11101
The Relevance of Mergers for Fueling AGNs: Answers from
QSO Host
Galaxies
The majority of QSOs are known to reside in centers of
galaxies that
look like ellipticals. Numerical simulations have shown
that remnants of
galaxy mergers often closely resemble elliptical galaxies.
However, it
is still strongly debated whether the majority of QSO host
galaxies are
indeed the result of relatively recent mergers or whether
they are
completely analogous to inactive ellipticals to which
nothing
interesting has happened recently. To address this
question, we recently
obtained deep HST ACS images for five QSO host galaxies
that were
classified morphologically as ellipticals {GO-10421}. This
pilot study
revealed striking signs of tidal interactions such as
ripples, tidal
tails, and warped disks that were not detected in previous
studies. Our
observations show that at least some
"elliptical" QSO host galaxies are
the products of relatively recent merger events rather
than old galaxies
formed at high redshift. However, the question remains
whether the host
galaxies of classical QSOs are truly distinct from
inactive ellipticals
and whether there is a connection between the merger
events we detect
and the current nuclear activity. We must therefore place
our results
into a larger statistical context. We are currently
conducting an HST
archival study of inactive elliptical galaxies {
control sample. We now propose to obtain deep HST/WFPC2
images of 13
QSOs whose host galaxies are classified as normal
ellipticals. Comparing
the results for both samples will help us determine
whether classical
QSOs reside in normal elliptical galaxies or not. Our
recent pilot study
of five QSOs indicates that we can expect exciting results
and deep
insights into the host galaxy morphology also for this
larger sample of
QSOs. A statistically meaningful sample will help us
determine the true
fraction of QSO hosts that suffered strong tidal
interactions and thus,
whether a merger is indeed a requirement to trigger
nuclear activity in
the most luminous AGNs. In addition to our primary science
observations
with WFPC2, we will obtain NICMOS3 parallel observations
with the
overall goal to select and characterize galaxy populations
at high
redshifts. The imaging will be among the deepest NICMOS
images: These
NICMOS images are expected to go to a limit a little over
1 magnitude
brighter than HUDF-NICMOS data, but over 13 widely
separated fields,
with a total area about 1.5 times larger than HUDF-
NICMOS. This
separation means that the survey will tend to average out
effects of
cosmic variance. The NICMOS3 images will have sufficient
resolution for
an initial characterization of galaxy morphologies, which
is currently
one of the most active and promising areas in approaching
the problem of
the formation of the first massive galaxies. The depth and
area coverage
of our proposed NICMOS observations will also allow a
careful study of
the mass function of galaxies at these redshifts. This
provides a large
and unbiased sample, selected in terms of stellar mass and
unaffected by
cosmic variance, to study the on-going star formation
activity as a
function of mass {i.e. integrated star formation} at this
very important
epoch.
FLIGHT OPERATIONS SUMMARY:
Significant Spacecraft Anomalies: (The following are
preliminary reports
of potential non-nominal performance that will be
investigated.)
HSTARS:
11438 - GSAcq (2,1,2) failed due to Scan Step Limit
Exceeded on FGS 2
At
acquisition of signal (228/11:48:04) GSAcq (2,1,2) had failed to RGA
Hold due to Scan Step Limit Exceeded on FGS 2. Received flags for
QF2SSLEX, QF2STOPF, QSTEPEXC and QSTOP. Pre-acquisition
Observations
affected: NICMOS Proposal 8795, Observation 172,
NICMOS Proposal 11202, Observation 173
REAcq (2,1,2) scheduled at 228/12:52:41 - 13:00:02 succeeded.
11440 - GSacq(1,3,1) not attempted.
GSacq(1,3,1)did not attempt to acquire due to no OBAD success flag. At
229/11:25:21 an ESB 1806 "T2G OPEN LOOP TIMEOUT" was received causing
a
unscheduled transition to M2G "OBD2 failed".
Observations affected: NIC 199 Proposal ID 08795
11444 - GSacq(1,2,1) resulted in Fine Lock Backup (1,0,1)
GSacq(1,2,1) scheduled at 229/14:52:33 resulted in fine lock backup
(1,0,1). Stop flags QF2STOPF and QSTOP were received at 14:55:42.
Observations affected: NIC 202 Proposal ID 11548, NIC 203 Proposal ID
08795
11446 - Guide Star Acquisition resulted in fine lock back
up (1,0,1)
GSAcq (1,2,1) scheduled at D231/08:22:35 resulted in fine lock back up
(1,0,1) @ 08:27:15 with QSTOP and QF2STOPF flags.
Observations affected: WFPC 17, 18, NICMOS 4, 5, & 6 (Proposal 11548)
COMPLETED OPS REQUEST: (None)
COMPLETED OPS NOTES: (None)
SCHEDULED
SUCCESSFUL
FGS GSacq
29
27
FGS REacq
15
15
OBAD with Maneuver
88
83
SIGNIFICANT EVENTS: (None)