Daily Report #4676

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 images. 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 z1

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 {AR- 10941} to form a 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)