Daily #4019

HUBBLE SPACE TELESCOPE - Continuing to collect World Class Science

DAILY REPORT # 4019

PERIOD COVERED: UT December 30,31, 2005 (DOY 364,365)
January 01,02, 2006 (DOY 001,002)

OBSERVATIONS SCHEDULED

NIC1/NIC2/NIC3 8792

NICMOS Post-SAA calibration - CR Persistence Part 3

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.

WFPC2 10778

WFPC2 WF4 Supplemental Darks

A serious anomaly has been found in images from the WF4 CCD in WFPC2.
The WF4 CCD bias level appears to have become unstable, resulting in
sporadic images with either low or zero bias level. The severity and
frequency of the problem is rapidly increasing, and it is possible
that WF4 will soon become unusable if no work-around is found. The
other three CCDs {PC1, WF2, and WF3} appear to be unaffected and
continue to operate properly. These darks are to supplement those in
program 10748 to ensure sufficient dark frames for routine
calibration. As the WF4 anomaly grows worse, we are beginning to see
episodes where too many darks are corrupted and are unusable.

ACS/HRC 10752

Cycle 14 Focus Monitor

The focus of HST is measured primarily with ACS/HRC over full CVZ
orbits to obtain accurate mean focus values via a well sampled
breathing curve. Coma and astigmatism are also determined from the
same data in order to further understand orbital effects on image
quality and optical alignments. To monitor the stability of ACS to
WFPC2 relative focii, we've carried over from previous focus monitor
programs parallel observations taken with the two cameras at suitable
orientations of previously observed targets, and interspersed them
with the HRC CVZ visits.

WFPC2 10751

WFPC2 CYCLE 14 Intflat Linearity Check and Filter Rotation Anomaly
Monitor

Intflat observations will be taken to provide a linearity check: the
linearity test consists of a series of intflats in F555W, in each gain
and each shutter. A combination of intflats, visflats, and earthflats
will be used to check the repeatability of filter wheel motions.
{Intflat sequences tied to decons, visits 1-18 in prop 10363, have
been moved to the cycle 14 decon proposal 10744 for easier
scheduling.} Note: long-exposure WFPC2 intflats must be scheduled
during ACS anneals to prevent stray light from the WFPC2 lamps from
contaminating long ACS external exposures.

WFPC2 10750

WFPC2 Cycle 14 UV Earth Flats

Monitor flat field stability. This proposal obtains sequences of earth
streak flats to improve the quality of pipeline flat fields for the
WFPC2 UV filter set. These Earth flats will complement the UV earth
flat data obtained during cycles 8-13.

WFPC2 10749

Earth Flats

This proposal monitors flatfield stability. This proposal obtains
sequences of Earth streak flats to construct high quality flat fields
for the WFPC2 filter set. These flat fields will allow mapping of the
OTA illumination pattern and will be used in conjuction with previous
internal and external flats to generate new pipeline superflats. These
Earth flats will complement the Earth flat data obtained during cycles
4-13.

WFPC2 10748

WFPC2 CYCLE 14 Standard Darks

This dark calibration program obtains dark frames every week in order
to provide data for the ongoing calibration of the CCD dark current
rate, and to monitor and characterize the evolution of hot pixels.
Over an extended period these data will also provide a monitor of
radiation damage to the CCDs.

ACS/HRC 10738

Earth Flats

Sky flats will be obtained by observing the bright Earth with the HRC
and WFC. These observations will be used to verify the accuracy of the
flats currently in the pipeline and to monitor any changes. Weekly
coronagraphic monitoring is required to assess the changing position
of the spots.

ACS/HRC/WFC 10733

CCD Hot Pixel Annealing

Hot pixel annealing will continue to be performed once every 4 weeks.
The CCD TECs will be turned off and heaters will be activated to bring
the detector temperatures to about +20C. This state will be held for
approximately 6 hours, after which the heaters are turned off, the
TECs turned on, and the CCDs returned to normal operating condition.
To assess the effectiveness of the annealing, a bias and four dark
images will be taken before and after the annealing procedure for both
WFC and HRC. The HRC darks are taken in parallel with the WFC darks.
The charge transfer efficiency {CTE} of the ACS CCD detectors declines
as damage due to on-orbit radiation exposure accumulates. This
degradation has been closely monitored at regular intervals, because
it is likely to determine the useful lifetime of the CCDs. We combine
the annealling activity with the charge transfer efficiency monitoring
and also merge into the routine dark image collection. To this end,
the CTE monitoring exposures have been moved into this proposal . All
the data for this program is acquired using internal targets {lamps}
only, so all of the exposures should be taken during Earth occultation
time {but not during SAA passages}. This program emulates the ACS
pre-flight ground calibration and post-launch SMOV testing {program
8948}, so that results from each epoch can be directly compared.
Extended Pixel Edge Response {EPER} and First Pixel Response {FPR}
data will be obtained over a range of signal levels for both the Wide
Field Channel {WFC}, and the High Resolution Channel {HRC}.

ACS/HRC/WFC 10729

ACS CCDs daily monitor

This program consists of a set of basic tests to monitor, the read
noise, the development of hot pixels and test for any source of noise
in ACS CCD detectors. The files, biases and dark will be used to
create reference files for science calibration. This programme will be
for the entire lifetime of ACS. Changes from cycle 13:- The default
gain for WFC is 2 e-/DN. As before bias frames will be collected for
both gain 1 and gain 2. Dark frames are acquired using the default
gain {2}. This program cover the period Oct, 2 2005- May, 29-2006. The
second half of the program has a different proposal number: 10758.

NIC1/NIC3 10726

NICMOS non-linearity tests

This program incorporates a number of tests to analyse the count rate
dependent non-linearity seen in NICMOS spectro-photometric
observations. In visit 1 we will observe a few fields with stars of a
range in luminosity in NGC1850 with NICMOS in NIC1 in F090M, F110W and
F160W and NIC2 F110W, F160W, and F180W. We will repeat the
observations with flatfield lamp on, creating artificially high
count-rates, allowing tests of NICMOS linearity as function of count
rate. To access the effect of charge trapping and persistence, we
first take darks {so there is not too much charge already trapped},
than take exposures with the lamp off, exposures with the lamp on, and
repeat at the end with lamp off. Finally, we continue with taking
darks during occultation. In visit 2 we will observe
spectro-photometric standard P041C using the G096 and G141 grisms in
NIC3, and repeat the lamp off/on/off test to artificially create a
high background. In visits 3&4 we repeat photometry measurements of
faint standard stars SNAP-2 and WD1657+343, on which the NICMOS
non-linearity was originally discovered using grism observations.
These measurements are repeated, because previous photometry was
obtained with too short exposure times, hence substantially affected
by charge trapping non-linearity. Measurements will be made with NIC1:
Visit 5 forms the persistence test of the program. The bright star
GL-390 {used in a previous persistence test} will iluminate the 3
NICMOS detectors in turn for a fixed time, saturating the center many
times, after which a series of darks will be taken to measure the
persistence {i.e. trapped electrons and the decay time of the traps}.
To determine the wavelength dependence of the trap chance, exposures
of the bright star in different filters will be taken, as well as one
in the G096 grism with NIC3. Most exposures will be 128s long, but two
exposures in the 3rd orbit will be 3x longer, to seperate the effects
of count rate versus total counts of the trap probability {in one
exposure, we get the full PSF worth of count rates, but we need a
longer exposure to separate the effect of rate versus total couts}.
Filters used: NIC1 F090M, F110W, F170M and F160W; NIC2 F110W, F160W,
F205W, F187W; NIC3 G096, F110W, F160W; 3x longer exposures: NIC1 and
NIC2 F110W.

ACS/HRC 10627

A Snapshot Survey of Post-AGB Objects and Proto-Planetary Nebulae

We propose an ACS/HRC snapshot survey of 50 post-AGB sources, objects
which have evolved from the AGB but may or may not become planetary
nebulae {PNe}. This survey will complement existing HST images of
proto-planetary nebulae {PPNe} and PNe in addressing circumstellar
envelope morphology as a function of: 1} the progenitor star mass; 2}
the chemical composition; and 3} evolutionary stage. We will connect
the observed diversity of nebualar shapes with the main physical and
chemical conditions characterizing post-AGB objects, to identify the
mechanism that breaks the symmetry of AGB mass loss. To our knowledge,
no previous HST projects have been specifically designed to address
this issue. From our database of 360 post-AGB candidates, we have
selected approximately 50 targets, none of which have been or are
being observed with HST, to sample different central star masses,
chemical compositions, and evolutionary stages, uniformly across the
sky. These new data will also provide important constraints to a
quantitative analysis of Spitzer Space Telescope {SST} observations
planned for a similar sample of objects. We will model the HST images
and SST spectra using our axisymmetric dust code 2-Dust, to derive
dust density distributions, pole to equator density ratios, dust shell
masses, inclination angles as well as dust composition.

ACS/WFC 10626

A Snapshot Survey of Brightest Cluster Galaxies and Strong Lensing to
z = 0.9

We propose an ACS/WFC snapshot survey of the cores of 150 rich galaxy
clusters at 0.3 z 0.9 from the Red Sequence Cluster Survey {RCS}.
An examination of the galaxian light in the brightest cluster
galaxies, coupled with a statistical analysis of the strong-lensing
properties of the sample, will allow us to contrain the evolution of
both the baryonic and dark mass in cluster cores, over an
unprecedented redshift range and sample size. In detail, we will use
the high- resolution ACS images to measure the metric {10 kpc/h}
luminosity and morphological disturbances around the brightest
clusters galaxies, in order to calibrate their accretion history in
comparison to recent detailed simulations of structure formation in
cluster cores. These images will also yield a well-defined sample of
arcs formed by strong lensing by these clusters; the frequency and
detailed distribution {size, multiplicity, redshifts} of these strong
lens systems sets strong constraints on the total mass content {and
its structure} in the centers of the clusters. These data will also be
invaluable in the study of the morphological evolution and properties
of cluster galaxies over a significant redshift range. These analyses
will be supported by extensive ongoing optical and near-infrared
imaging, and optical spectroscopy at Magellan, VLT and Gemini
telescopes, as well as host of smaller facilities.

ACS/HRC 10623

HST Optical Snapshot Survey of Intermediate Redshift Ultraluminous
Infrared Galaxies

Ultraluminous infrared galaxies {ULIGs} are commonly believed to be a
transitory phase in the evolution of disk galaxy mergers into QSOs.
However, a recently reported discrepancy between the morphological and
structural properties of z 0.13 ULIGs and z = 0.12-0.25 QSOs with
M{V} -23.5 has cast doubt on their evolutionary connection. We
propose an ACS snapshot survey of a sample of 39 ULIGs with z =
0.35-1.0. These galaxies are the best suited for comparison with
luminous z=0.12-0.25 QSOs because {1} they are at larger lookback
times than local ULIGs, and thus are likely representative of the
systems that evolve into lower redshift luminous QSOs, {2} they have
luminosities comparable to luminous QSOs and, {3} they are selected in
a manner that biases the sample towards harboring imbedded AGN, and
thus are the most likely precursors to optical QSOs. High resolution
HST ACS images will allow a determination of galaxy morphology and
reveal the presence of bright AGN. The 2-D profile of each galaxy will
be modeled using GALFIT, with the AGN comprising one component of the
fit where applicable to better characterize the underlying galaxy.
Fundamental parameters {effective radius and surface brightness, and
F814W-band magnitude} of the underlying galaxy will thus be measured
and compared with the host galaxies of the luminous QSO sample. This
imaging campaign will consume a modest amount of HST time, but will
provide for the first time a statistically significant view of ULIGs
at look-back times of 30-65% the age of the universe, and sufficient
resolution and sensitivity to conduct a meaningful comparison with
z=0.12-0.25 QSOs, as well as with local {z 0.3} IRAS-detected and
distant {z 2} SCUBA-detected ULIGs.

FGS 10612

Binary Stars in Cyg OB2: Relics of Massive Star Formation in a
Super-Star Cluster

We propose to make a high angular resolution SNAP survey of the
massive stars in the nearby, super-star cluster Cyg OB2. We will use
FGS1r TRANS mode observations to search for astrometric companions in
the separation range of 0.01 to 1.00 arcsec and in the magnitude
difference range smaller than 4 magnitudes. The observations will test
the idea that the formation of very massive stars involves mergers and
the presence of nearby companions. Discovery of companions to massive
stars in this relatively nearby complex will provide guidance in the
interpretation of apparently supermassive stars in distant locations.
The search for companions will also be important for verification of
fundamental parameters derived from spectroscopy, adjustments to main
sequence fitting and distance estimations, determining third light
contributions of eclipsing binaries, identifying wide colliding wind
binaries, studying the relationship between orbital and spin angular
momentum, and discovering binaries amenable to future mass
determinations. The massive star environment in Cyg OB2 may be similar
to the kinds found in the earliest epoch of star formation, so that a
study of the role of binaries in Cyg OB2 will help us understand the
formation processes of the first stars in the Universe.

WFPC2 10608

Probing the star formation law in the extreme outer limits of M83, a
prototypical XUV-disk galaxy

The Galaxy Evolution Explorer {GALEX} has discovered a new sub-class
of spiral galaxy, which we refer to as extended UV-disk {XUV-disk}
galaxies. They are distinguished by conspicuous UV-bright star
clusters located at galactocentric radii extending to many times the
optical {R25} extent, and appear to represent a population of spiral
galaxies still actively building, or augmenting, their stellar disk.
However, XUV-disks pose a mystery in the form of a relative lack of
HII regions {traced by H-alpha emission} associated with outer disk,
UV-bright stellar clusters. M83 is an XUV-disk prototype and the focus
of this proposal. It has an H-alpha surface brightness profile
characterized by a steep decline at the radius beyond which the
gaseous disk is thought to become dynamically stable {against collapse
and ensuing star formation}, but GALEX UV profiles show no "edge" at
this location. Our HST study of M83 aims to resolve this puzzling
discrepancy, confirmed in several XUV-disks, by searching for
Lyman-continuum producing O stars that are either absent or present
without nebulosity. HST provides the only means of resolving
individual massive stars in the FUV band at M83's distance. Without
HST, we lose the critical ability to photometrically classify O and B
stars. Our multiwavelength observations will also constrain the
history of star formation in the outer disk over Gyr timescales by
characterizing the evolved stellar population, both using resolved
giants and color analysis of the diffuse background.

ACS/HRC 10602

A Complete Multiplicity Survey of Galactic O2/O3/O3.5 Stars with ACS

Massive stars are preferentially formed in compact multiple systems
and clusters and many of them remain spatially unresolved to date,
even in our Galaxy. This has hindered the determination of the stellar
upper mass limit. The lack of an accurate knowledge of the
multiplicity of massive stars can also introduce biases in the
calculation of the IMF at its high-mass end. We have recently used
ACS/HRC to resolve HD 93129 A, the earliest O-type star known in the
Galaxy, into a 55 mas binary. We propose here to extend that work into
a complete multi-filter ACS imaging survey of all {20} known
O2/O3/O3.5 Galactic stars to characterize the multiplicity of the most
massive stars. The data will be combined with existing FGS
observations to explore as large a parameter range as possible and to
check for consistency. We will also derive the IMF of each system
using a crowded-field photometry package and processing the data with
CHORIZOS, a code that can derive stellar temperatures, extinctions,
and extinction laws from multicolor photometry.

WFPC2/ACS/WFC 10590

Star-Formation History of an Unmerged Fragment: the Leo A Dwarf Galaxy

The Leo A dwarf irregular is the only known Local Group galaxy that on
the weight of current evidence has been suggested to have experienced
its first star formation within the past 2-3 billion years. As a
galaxy that could have been almost purely gaseous during the epoch of
giant galaxy assembly, Leo A is the best nearby candidate to be a
redshift zero analogue to the major building blocks of the Milky Way.
We propose to obtain deep optical images of Leo A with the ACS/WFC to
achieve three main goals: 1} To establish the fractions of
star-formation, by mass, that occurred prior and subsequent to the
main epoch of hierarchical merging {redshift z ~ 2-4, Age ~ 10-12.5
Gigayears}; 2} to measure the time variation in Leo A's star-formation
rate over the past 10 Gyr, based on statistical analyses of its {V-I,
I} color-magnitude diagram; and 3} to measure the radial distributions
of young and old stellar populations and quantify the degree to which
the optically prominent, young population is embedded in an extended,
low-surface brightness sheet or halo of ancient stars. Because of the
distance modulus {24.5 mag} and high degree of stellar crowding at the
level of the oldest main-sequence turnoffs, the observations necessary
to achieve these goals are unobtainable except with HST. The ONLY way
to reliably derive the star-formation history of Leo A over its entire
lifetime is with photometry to magnitudes of {B, I} = {28.6, 27.9},
the level of the oldest main-sequence turnoff in Leo A. These data
would confirm and extend the limited inferences obtained from WFPC2
photometry over 2 magnitudes less deep, and provide the first
opportunity to measure the complete star-formation history of a
potential "living fossil" analogue to the building blocks of the Milky
Way. We propose to use WFPC2 in parallel to measure radial variations
in the stellar populations between the galaxy's core and outskirts.
Because the expected 2-gyro jitter ellipse is comparable to the pixel
scale of ACS/WFC, we rely on point-spread function fitting photometry,
and we require no special scheduling constraints, our proposed program
would be virtually unaffected by entry into 2-gyro mode.

ACS/WFC 10586

The Rosetta Stone without a Distance: Hunting for Cepheids in the
Primordial Galaxy I Zw 18

The Blue Compact Dwarf galaxy I Zw 18 is one of the most intriguing
objects in the Local Universe. It has the lowest nebular metallicity
of all known galaxies {Z=1/32 solar}. It has long been regarded as a
possible example of a galaxy undergoing its first burst of star
formation. However, its real evolutionary state continues to be
controversial. The WFPC2 and NICMOS detection of AGB stars by our
group and others suggested the presence of an underlying older
population. However, deeper ACS observations by Izotov & Thuan {2004}
recently failed to detect the signature of RGB stars. This was
interpreted as confirmation that I Zw 18 is in fact a galaxy "in
formation", a local analog of primordial galaxies in the distant
Universe. This result was widely reported in the international news
media. However, an alternative possibility is that I Zw 18 is somewhat
further away than previously believed, so that Red Giant Branch stars
were too faint to detect. Quoted distances in the literature have
ranged from 10 to 20 Mpc. We intend to resolve this controversy by
direct determination of the distance to 1 Mpc accuracy using Cepheids.
For this we request 12 visits of two orbits each, to execute at
carefully planned intervals. We will obtain V and I band ACS/WFC
photometry in each visit. The new data will be combined with archival
data, but we show that the archival data by themselves are
insufficient to achieve our science goals. The distance will allow us
to place I Zw 18 into its proper place in the evolutionary sequence of
galaxy formation.

ACS/WFC 10580

A tip of the red giant branch distance to NGC 4038/39 {The Antennae}

We propose to use ACS to determine a tip of the red giant branch
{TRGB} distance to the merger system archetype NGC4038/39 {"The
Antennae"}. This system is the closest major merger to us, but its
distance remains a point of debate, with proposed values ranging from
14 to 33 Mpc. Our previous HST/WFPC2 V, I band observation targeted
the star forming {SF} regions near the tip of the southern tail of
NGC4038. These data revealed a background population of red stars far
from SF regions which we identify as RGB stars. The TRGB was detected
near our completeness limit at about 26.5 mag, suggesting a distance
of 13.8+/-1.7 Mpc, 30% lower than the most accepted distance of 21
Mpc, and less than half the distance of 29 Mpc adopted to characterize
the "ultraluminous X-ray binaries" {UXB} sources discovered in recent
Chandra observations by Fabbiano et al. {2001}. The lower distance has
profound implications for the mass and luminosities of all sources
associated with The Antennae, such as the Tidal Dwarf candidates, the
globular cluster system, and the UXB population. With its greater
sensitivity and higher resolution, ACS can resolve this issue in just
a few orbits. We therefore request seven orbits to obtain V, I band
images of the southern tail of NGC4038/39 to reach 1.6 mag lower than
the TRGB, for our proposed distance modulus. Even if the larger
distance is the correct one, our proposed imaging would still give a
robust distance constraint from the TRGB.

ACS/WFC 10574

Witnessing Galaxy Transformation in Galaxy Groups at z 1

The recent discover of five galaxy groups in the Lynx supercluster
region offers us the exciting opportunity to observe for the first
time groups in the process of collapsing into a merging pair of
clusters at z 1. Our current picture of structure formation suggests
that substantial evolution of galaxy properties can occur in groups
and filaments well before they enter the environs of massive clusters.
However, neither current theoretical models nor observations give us a
complete understanding of the relative importance of the different
physical processes that control the structural and spectral
transformations that occur prior to, during, and after infall into a
dense environment. We propose direct observation of these newly
discovered dynamically young structures in the Lynx region, in order
to provide a critical benchmark in testing not only whether galaxy
evolution occurs mostly prior to entry into the densest regions but
will also constrain the relative importance of initial conditions in
determining the fate of galaxy systems. Our analysis of these proposed
ACS measurements will be complemented with an unique dataset we have
already in the optical, infrared, mid-infrared, and X-ray.

ACS/HRC 10559

Astrometric monitoring of binary L and T dwarfs

We propose to obtain high angular resolution ACS images of five binary
L and T dwarfs in order to determine their orbital parameters and
dynamical masses, and directly constrain the evolutionary models of
ultracool and substellar objects. The binaries have estimated periods
ranging between 5 and 14 years. All of them have already been resolved
at least twice {sometimes more} using HST, providing first and second
epochs measurements. We propose to obtain two more ACS imaging
observations separated by 9 to 12 months during cycle 14. The expected
period coverage should therefore range between 35% and 117%, allowing
us to compute precise orbital parameters and masses. Our sample is
large enough and covers a sufficiently wide range of spectral types
{from L3 to T5.5} to allow us to obtain strong constraints the
evolutionnary models.

ACS/HRC 10555

A Search for Satellites Around Kuiper Belt Objects Which Exhibit High
Angular Momentum

We propose to use the HST to search for satellites around Kuiper Belt
Objects which have large amplitude, fast rotational light curves.
Large main belt asteroids with similar light curve characteristics
have been found to have near an 80 percent companion rate. This is
over an order of magnitude more than the companion rate of main belt
asteroids in general. The satellites were probably formed during the
process which imparted the high angular momentum on the primary
object. To date five Kuiper Belt objects exhibit high angular momentum
through their rotational light curves. Two of them have been observed
with STIS on the HST and one was found to be a binary. We request
three orbits with HST/ACS in order to obtain deep high resolution
images of the other three Kuiper Belt objects that have large
amplitudes and fast rotations. In addition, we request one orbit to
reobserve the other KBO which didn't have a satellite detection in
order to obtain deeper and better resolution images than the first
observations. Finding binaries is important not only to understand the
processes which created the high angular momentum of the primary but
also in determining the bulk densities and collisional histories of
the objects.

ACS/SBC 10554

Globular Cluster Systems of Elliptical Galaxies in Low Density
Environments

We propose to use the ACS/WFC to determine colour {metallicity}
distributions and luminosity functions for the globular cluster
populations in a well-defined sample of elliptical galaxies in low-
density environments, and to compare the results with similar samples
taken from a rich cluster environment. Low-luminosity ellipticals are
now recognized to play a pivotal role in testing hierarchical models
of galaxy formation, and their globular cluster populations provide a
unique probe of their star formation and metal enrichment history. The
data will be used to {i} determine whether the bimodal colour
distributions indicative of multiple formation epochs in luminous
ellipticals are also prevalent in low-luminosity field ellipticals;
{ii} place joint constraints on age and metallicity in systems with
more than one population and determine the spread of ages in any one
system; {iii} test whether cluster destruction processes {e.g. tidal
shocking} are more effective in low-luminosity ellipticals, as
predicted from their higher mass densities. ACS observations are
essential to eliminate foreground/background contamination and to
probe deep into the luminosity function to obtain a good statistical
sample of clusters. The TAC has previously awarded HST time to two
large surveys of globular cluster systems in rich cluster
environments, but there is currently no comparable survey in
low-density environments with which to compare these results.

ACS/WFC 10522

Calibrating Star Formation: The Link between Feedback and Galaxy
Evolution

Stellar feedback - the return of mass and energy from star formation
to the interstellar medium - is one of the primary engines of galaxy
evolution. Yet, the theoretical foundation of mechanical feedback is,
to date, unconstrained by observations. We propose to investigate this
fundamental aspect of star formation on a sample of two local actively
star-forming galaxies, NGC4449, and Holmberg II. The two galaxies have
been selected to occupy an unexplored, yet crucial for quantifying
mechanical feedback, niche in the two-parameter space of star
formation intensity and galaxy mass. ACS/WFC and WFPC2 narrow-band
observations in the light of H-beta, [OIII], H-alpha, and [NII] will
be obtained for both galaxies, in order to: {1} discriminate the
feedback- induced shock fronts from the photoionization regions; {2}
map the shocks inside and around the starburst regions; and {3}
measure the energy budget of the star-formation-produced shocks. These
observations, complemented by existing data, will yield: {1} the
efficiency of the feedback, i.e. the fraction of the star formation's
mechanical energy that is transported out of the starburst volume
rather than confined or radiated away; {2} the dependence of this
efficiency on the two fundamental parameters of star formation
intensity and stellar mass. The high angular resolution of HST is
crucial for separating the spatially narrow shock fronts {~5 pc,
~0.25" at 4 Mpc} from the more extended photoionization fronts. The
legacy from this project will be the most complete quantitative
measurement of the energetics associated with feedback processes. We
will secure the first milestone for placing feedback mechanisms on a
solid physical ground, and for understanding quantitatively their role
on the energetics, structure, and star formation history of galaxies
at all redshifts.

NIC2 10510

Morphology of massive early-type galaxies at z1.2: constraining
galaxy formation models

We ask for NICMOS-NIC2 H-band imaging of a sample of 10 massive
early-type galaxies spectroscopically identified at 1.2z1.7. Our aim
is to look for possible relics of merging events of their
formation/evolution in their morphology. The requested observations,
sampling their rest- frame at lambda6500A, would map the mass
distribution of the bulk of their stellar content. The targets have
been revealed by our group on the basis of near-IR spectroscopy
obtained in the framework of a spectroscopic survey of a complete
sample of bright EROs {Ks18.5}. Optical and near-IR photometry is
available for all the targets, and low resolution near-IR spectra have
allowed their identification and redshift measurement. Spectroscopic
and photometric data in our hands show that they have already
assembled stellar masses greater than 3 10^11 solar masses, and that
the mean age of their stellar population is estimated older than 2-3
Gyr for 6 of them and about 1 Gyr for the other 4 galaxies. Thus, they
are among the most luminous and massive evolved galaxies detected so
far at z1. Other data are needed to infer how they have assembled
such high stellar masses, i.e. to trace back their evolution. The
requested observations would allow us to reveal signs of past
interaction/merger event. A smooth r^{1/m} profile, coupled with no
other signs of interaction/merger {disturbed morphology}, would place
the possible merger event of formation 1-2 Gyr before their redshift z
pprox 1.5, i.e. at z 2-3. On the other hand, if signs of recent
merger events will be found, the last merger event forming the local
massive spheroids will be constrained at 1.5 z 2. Thus, the
requested HST observations will allow for the first time to see how
massive early-type galaxies at z pprox 1.5 look like, constraining in
any case the redshift of the possible merging event of their
formation.

ACS/WFC/WFPC2 10499

Life Before the Fall: Morphological Evolution of Galaxies in Groups
Prior to Cluster Assembly at z=0.37

We propose to obtain a deep ACS/WFC mosaic of a protocluster comprised
of 4 distinct galaxy groups that are gravitationally bound to each
other at z=0.37. The galaxy groups have a total combined mass
comparable to the Coma cluster and already have twice as many
absorption line galaxies as the field. The SG1120 complex thus
provides an unprecedented opportunity for determining whether
"pre-processing" in the group environment is responsible for the bulk
of observed diffences between galaxies in nearby clusters and those in
the field. High resolution imaging with HST is needed to
morphologically classify the group members and measure their
structural parameters. By combining the early-type fraction and
morphology-density relation in SG1120 with results from our wide-field
spectroscopic survey, we will test whether spectral and morphological
transformation timescales are decoupled on group scales and isolate
the environmental mechanisms responsible for such evolution. We will
also measure the Fundamental Plane and M/L ratios of the early-type
members to constrain their formation epoch and how their stellar
populations have evolved. Observations of the multiple galaxy groups
in SG1120 provide a unique dataset to the community and will aid our
understanding of how galaxies evolve in the still poorly studied group
regime.

ACS/WFC 10497

Cepheid Calibrations of the Luminosity of Two Reliable Type Ia
Supernovae and a Re- determination of the Hubble Constant

We propose to determine the luminosity of two type Ia supernovae {SNe
Ia}, 1995al in NGC 3021 and SN 2002fk in NGC 1309, by observing
Cepheids in their spiral hosts. Modern CCD photometry yields an
extremely tight Hubble diagram for SNe Ia with a precisely determined
intercept {i.e., Delta H_0/H_0}. Yet, the measurement of the true
Hubble constant via SNe Ia is limited by the calibration derived from
problematic and unreliable SN data. Most of the SNe Ia calibrated by
HST to date are significantly compromised by the systematics of
photographic photometry, high reddening and SN peculiarity, and by the
photometric anomolies associated with WFPC2. The extended reach of ACS
now provides opportunities to more reliably calibrate SNe Ia and H_0.
Our Cepheid calibration of a reliable SN Ia dataset, SN 1994ae, using
ACS in Cycle 11 resulted in a 15% increase in H_0 from the value
derived by the HST SN Ia Calibration Program. Yet, there remains a
terribly small sample of reliable SN Ia data sets on which to base
such a crucial cosmological result. SN 1995al and SN 2002fk are two of
the best observed SNe Ia both with little reddening. They provide two
opportunities to use ACS for placing the calibration of H_0 via SN Ia
on firmer footing and potentially improve its precision.

ACS/WFC 10496

Decelerating and Dustfree: Efficient Dark Energy Studies with
Supernovae and Clusters

We propose a novel HST approach to obtain a dramatically more useful
"dust free" Type Ia supernovae {SNe Ia} dataset than available with
the previous GOODS searches. Moreover, this approach provides a
strikingly more efficient search-and-follow-up that is primarily pre-
scheduled. The resulting dark energy measurements do not share the
major systematic uncertainty at these redshifts, that of the
extinction correction with a prior. By targeting massive galaxy
clusters at z 1 we obtain a five-times higher efficiency in
detection of Type Ia supernovae in ellipticals, providing a
well-understood host galaxy environment. These same deep cluster
images then also yield fundamental calibrations required for future
weak lensing and Sunyaev-Zel'dovich measurements of dark energy, as
well as an entire program of cluster studies. The data will make
possible a factor of two improvement on supernova constraints on dark
energy time variation, and much larger improvement in systematic
uncertainty. They will provide both a cluster dataset and a SN Ia
dataset that will be a longstanding scientific resource.

ACS/WFC 10493

A Survey for Supernovae in Massive High-Redshift Clusters

We propose to measure, to an unprecedented 30% accuracy, the SN-Ia
rate in a sample of massive z=0.5-0.9 galaxy clusters. The SN-Ia rate
is a poorly known observable, especially at high z, and in cluster
environments. The SN rate and its redshift dependence can serve as
powerful discrimiminants for a number of key issues in astrophysics
and cosmology. Our observations will: 1. Put clear constraints on the
characteristic SN-Ia "delay time, " the typical time between the
formation of a stellar population and the explosion of some of its
members as SNe-Ia. Such constraints can exclude entire categories of
SN-Ia progenitor models, since different models predict different
delays. 2. Help resolve the question of the dominant source of the
high metallicity in the intracluster medium {ICM} - SNe-Ia, or
core-collapse SNe from an early stellar population with a top-heavy
IMF, perhaps those population III stars responsible for the early
re-ionization of the Universe. Since clusters are excellent
laboratories for studying enrichment {they generally have a simple
star-formation history, and matter cannot leave their deep
potentials}, the results will be relevant for understanding metal
enrichment in general, and the possible role of first generation stars
in early Universal enrichment. 3. Reveal, via nuclear variability, the
AGN fraction in clusters at this redshift, to be compared with the
field AGN fraction. This will be valuable input for understanding
black-hole demographics, AGN evolution, and ICM energetics. 4.
Potentially discover intergalactic cluster SNe, which can trace the
stripped stellar population at high z.

ACS/HRC 10476

Accurate Mass Determination of the Ancient White Dwarf ER 8 Through
Astrometric Microlensing

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.

NIC3/ACS/WFC 10404

The Nature of Protocluster Galaxies at z=2.16: Morphology-Density and
Color-Magnitude Relations

To establish the epoch when galaxy environment manifests itself as a
large-scale evolutionary process, we propose to extend the study of
galaxy colors and morphologies to a protocluster at z=2.16. Here the
universe is only 3 Gyrs old and significant differences are expected
between scenarios favoring a morphology-radius relation over a
morphology-density relation. In addition, because the fractional age
differences among cluster galaxies are larger, study of the color-
magnitude relation provides considerable leverage for determining the
epoch of early-type galaxy formation. To facilitate direct comparison
to studies at lower redshift, one must probe the same rest-frame
wavelengths with high photometric accuracy and at similar physical
scales. Its near-infrared photometric stability {low, constant
background} and ability to image large areas of sky at high
angular-resolution {compared to adaptive optics} makes HST/NICMOS
ideal for this program. Six pointings of NICMOS camera 3 will result
in rest-frame optical, high resolution images of 16 confirmed
protocluster members, and an additional 60 candidate protocluster
members including 29 EROs. These galaxies were selected with a variety
of techniques and span a range of projected radii within the
protocluster. The proposed observations constitute a unique
opportunity to extend the study of galaxies in overdense regions to an
early time in cosmic history.

ACS/WFC/WFPC2/NIC3 10395

Environmental drivers of galaxy evolution: an HST survey of dwarf
galaxy morphologies in the Abell

Galaxies in dense environments are subject to numerous physical
processes that leave a lasting impact, yet studies of galaxy evolution
to date have been limited to the most luminous galaxies -- those least
sensitive to environmental influence. We propose to explore the
environmental drivers of DWARF galaxy evolution: with a mosaic of 9x9
ACS pointings in F606W we will determine morphologies for ~1200
galaxies down to M_V=-14 in the A901/902 supercluster, spanning 3x3
Mpc at z=0.16. The deep ACS data will allow us to probe their surface
brightness profiles, shapes, sizes, asymmetry and fine structure such
as tidal features. With the addition of extensive existing
multi-wavelength data, we will probe the dependence of these important
parameters on dark matter content {from weak lensing maps}, the hot
intercluster medium {from deep XMM-Newton imaging}, and local galaxy
density {from hyper-accurate COMBO-17 photometric redshifts with delta
z=0.02 to m_R=24}, thus disentangling the various environmental
processes shaping dwarf galaxy evolution. Furthermore, the 8000+
background galaxies at 0.2z1.0 will be of enormous scientific
benefit for additional studies of weak lensing, AGN host galaxies, the
morphology-density relation, and the merger rate as a function of
redshift.

FLIGHT OPERATIONS SUMMARY:

Significant Spacecraft Anomalies: (The following are preliminary
reports of potential non-nominal performance that will be
investigated.)

HSTARS:

10068 - GSacq(2,1,2) failed @365/0409z GSacq(2,1,2) scheduled at
365/04:02:05 failed due to search radius limit exceeded on FGS 1. ESB
a05 (FGS Coarse Trac failed- Search Radius Limit exceeded) was
received. The map at 04:10:36 showed errors of V1=6.68, V2=116.71,
V3=3.69, RSS=116.96. OBAD1 showed errors of V1= 197.90, V2=-6272.32,
V3=421.57, RSS=6289.59. OBAD2 showed errors of V1=-0.29, V2=10.80,
V3=-1.54, RSS=10.92.


COMPLETED OPS REQUEST:
17615-0 - Genslew for Proposal 10695 - Slot-4 @002/0116z
17616-0 - Genslew for Proposal 10695 - Slot-3 @002/0117z

COMPLETED OPS NOTES: (None)

SCHEDULED SUCCESSFUL FAILURE TIMES
FGS
GSacq 37 36
365/0409z(HSTAR#10068)
FGS REacq 23 23
OBAD with Maneuver 112 112

SIGNIFICANT EVENTS: (None)