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Daily Report #4558



 
 
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Old March 3rd 08, 04:13 PM posted to sci.astro.hubble
Cooper, Joe
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Posts: 568
Default Daily Report #4558

HUBBLE SPACE TELESCOPE - Continuing to collect World Class Science

DAILY REPORT***** # 4558

PERIOD COVERED: UT February 29,March 01,02, 2008 (DOY 060,061,062)

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.

WFPC2 11289

SL2S: The Strong Lensing Legacy Survey

Recent systematic surveys of strong galaxy-galaxy lenses {CLASS,
SLACS, GOODS, etc.} are producing spectacular results for galaxy
masses roughly below a transition mass M~10^13 Mo. The observed lens
properties and their evolution up to z~0.2, consistent with numerical
simulations, can be described by isothermal elliptical potentials. In
contrast, modeling of giant arcs in X-ray luminous clusters {halo
masses M ~10^13 Mo} favors NFW mass profiles, suggesting that dark
matter halos are not significantly affected by baryon cooling. Until
recently, lensing surveys were neither deep nor extended enough to
probe the intermediate mass density regime, which is fundamental for
understanding the assembly of structures. The CFHT Legacy Survey now
covers 125 square degrees, and thus offers a large reservoir of strong
lenses probing a large range of mass densities up to z~1. We have
extracted a list of 150 strong lenses using the most recent CFHTLS
data release via automated procedures. Following our first SNAPSHOT
proposal in cycle 15, we propose to continue the Hubble follow-up
targeting a larger list of 130 lensing candidates. These are
intermediate mass range candidates {between galaxies and clusters}
that are selected in the redshift range of 0.2-1 with no a priori
X-ray selection. The HST resolution is necessary for confirming the
lensing candidates, accurate modeling of the lenses, and probing the
total mass concentration in galaxy groups up to z~1 with the largest
unbiased sample available to date.

NIC2 11237

The origin of the break in the AGN luminosity function

We propose to use NICMOS imaging to measure rest-frame optical
luminosities and morphological properties of a complete sample of
faint AGN host galaxies at redshifts z ~ 1.4. The targets are drawn
from the VLT-VIMOS Deep Survey, and they constitute a sample of the
lowest luminosity type 1 AGN known at z 1. The spectroscopically
estimated black hole masses are up to an order of magnitude higher
than expected given their nuclear luminosities, implying highly
sub-Eddington accretion rates. This exactly matches the prediction
made by recent theoretical models of AGN evolution, according to which
the faint end of the AGN luminosity function is populated mainly by
big black holes that have already exhausted a good part of their fuel.
In this proposal we want to test further predictions of that
hypothesis, by focussing on the host galaxy properties of our
low-luminosity, low- accretion AGN. If the local ratio between black
hole and bulge masses holds at least approximately at these redshifts,
one expects most of these low-luminosity AGN to reside in fairly big
ellipticals with stellar masses around and above 10^11 solar masses
(in contrast to the Seyfert phenomenon in the local universe). With
NICMOS imaging we will find out whether that is true, implying also a
sensitive test for the validity of the M_BH/M_bulge relation at z ~
1.4.

FGS 11211

An Astrometric Calibration of Population II Distance Indicators

In 2002 HST produced a highly precise parallax for RR Lyrae. That
measurement resulted in an absolute magnitude, M{V}= 0.61+/-0.11, a
useful result, judged by the over ten refereed citations each year
since. It is, however, unsatisfactory to have the direct,
parallax-based, distance scale of Population II variables based on a
single star. We propose, therefore, to obtain the parallaxes of four
additional RR Lyrae stars and two Population II Cepheids, or W Vir
stars. The Population II Cepheids lie with the RR Lyrae stars on a
common K-band Period-Luminosity relation. Using these parallaxes to
inform that relationship, we anticipate a zero-point error of 0.04
magnitude. This result should greatly strengthen confidence in the
Population II distance scale and increase our understanding of RR
Lyrae star and Pop II Cepheid astrophysics.

FGS 11210

The Architecture of Exoplanetary Systems

Are all planetary systems coplanar? Concordance cosmogony makes that
prediction. It is, however, a prediction of extrasolar planetary
system architecture as yet untested by direct observation for main
sequence stars other than the Sun. To provide such a test, we propose
to carry out FGS astrometric studies on four stars hosting seven
companions. Our understanding of the planet formation process will
grow as we match not only system architecture, but formed planet mass
and true distance from the primary with host star characteristics for
a wide variety of host stars and exoplanet masses. We propose that a
series of FGS astrometric observations with demonstrated 1 millisecond
of arc per-observation precision can establish the degree of
coplanarity and component true masses for four extrasolar systems: HD
202206 {brown dwarf+planet}; HD 128311 {planet+planet}, HD 160691 = mu
Arae {planet+planet}, and HD 222404AB = gamma Cephei {planet+star}. In
each case the companion is identified as such by assuming that the
minimum mass is the actual mass. For the last target, a known stellar
binary system, the companion orbit is stable only if coplanar with the
AB binary orbit.

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.

NIC3 11195

Morphologies of the Most Extreme High-Redshift Mid-IR-luminous
Galaxies II: The `Bump' Sources

The formative phase of some of the most massive galaxies may be
extremely luminous, characterized by intense star- and AGN-formation.
Till now, few such galaxies have been unambiguously identified at high
redshift, and thus far we have been restricted to studying the
low-redshift ultraluminous infrared galaxies as possible analogs. We
have recently discovered a sample of objects which may indeed
represent this early phase in galaxy formation, and are undertaking an
extensive multiwavelength study of this population. These objects are
optically extremely faint {R26} but nevertheless bright at
mid-infrared wavelengths {F[24um] 0.5 mJy}. Mid-infrared
spectroscopy with Spitzer/IRS reveals that they have redshifts z~2,
implying luminosities ~1E13 Lsun. Their mid-IR SEDs fall into two
broad, perhaps overlapping, categories. Sources with brighter F[24um]
exhibit power-law SEDs and SiO absorption features in their mid-IR
spectra characteristic of AGN, whereas those with fainter F[24um] show
a "bump" characteristic of the redshifted 1.6um peak from a stellar
population, and PAH emission characteristic of starformation. We have
begun obtaining HST images of the brighter sources in Cycle 15 to
obtain identifications and determine kpc-scale morphologies for these
galaxies. Here, we aim to target the second class {the "bump" sources}
with the goal of determining if these constitute morphologically
different objects, or simply a "low-AGN" state of the brighter class.
The proposed observations will help us determine whether these objects
are merging systems, massive obscured starbursts {with obscuration on
kpc scales!} or very reddened {locally obscured} AGN hosted by
intrinsically low-luminosity galaxies.

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.

NIC3 11153

The Physical Nature and Age of Lyman Alpha Galaxies

In the simplest scenario, strong Lyman alpha emission from high
redshift galaxies would indicate that stellar populations younger than
10 Myrs dominate the UV. This does not, however, constrain the stellar
populations older than 100 Myrs, which do not contribute to UV light.
Also, the Lyman alpha line can be boosted if the interstellar medium
is both clumpy and dusty. Different studies with small samples have
reached different conclusions about the presence of dust and old
stellar populations in Lyman alpha emitters. We propose HST- NICMOS
and Spitzer-IRAC photometry of 35 Lyman-alpha galaxies at redshift
4.5z6.5, in order to determine their spectral energy distribution
{SED} extending through rest-frame optical. This will allow us to
measure accurately {1} The total stellar mass in these objects,
including old stars which may have formed at redshifts {z 8} not
easily probed by any other means. {2} The dust extinction in the
rest-frame UV, and therefore a correction to their present
star-formation rates. Taken together, these two quantities will yield
the star-formation histories of Lyman alpha galaxies, which form fully
half of the known galaxies at z=4-6. They will tell us whether these
are young or old galaxies by straddling the 4000A break. Data from
NICMOS is essential for these compact and faint {i=25-26th magnitude
AB} high redshift galaxies, which are too faint for good near-IR
photometry from the ground.

WFPC2 11146

The Role of Stellar Feedback in 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 observational canvass of feedback is incomplete.
We propose to investigate this fundamental aspect of star formation on
one local actively star-forming galaxy, He2-10, selected to occupy an
unexplored niche in the key parameter space of stellar mass. The WFPC2
narrow-band observations in the light of H-beta, [OIII], H-alpha, and
[SII] will: {1} discriminate the feedback-induced shock fronts from
the photoionized regions; {2} map, and provide a complete census of,
the shocks inside and around the starburst regions; and {3} measure
the energy budget of the star-formation-produced shocks. These
observations, joined by our previous data and studies on starbursts,
will yield: {1} the efficiency of the feedback, i.e. the fraction of
the star formation's mechanical energy transported out of the
starburst volume rather than radiated away, in the dual-parameter
space of host's stellar mass and star formation intensity; {2} the
conditions under which feedback morphs from a localized process to a
galactic scale mechanism. The high angular resolution of HST is
crucial for separating the spatially narrow shock fronts {~10 pc=0.2"
at 10 Mpc} from the more extended photoionization fronts. This project
will provide the most comprehensive quantitative foundation of stellar
feedback and a gauge for determining the role of feedback in the
energetics, structure and star formation history of galaxies.

NIC2 11142

Revealing the Physical Nature of Infrared Luminous Galaxies at 0.3

We aim to determine physical properties of IR luminous galaxies at
0.3z2.7 by requesting coordinated HST/NIC2 and MIPS 70um observations
of a unique, 24um flux-limited sample with complete Spitzer mid-IR
spectroscopy. The 150 sources investigated in this program have S{24um}
0.8mJy and their mid-IR spectra have already provided the majority

targets with spectroscopic redshifts {0.3z2.7}. The proposed
150~orbits of NIC2 and 66~hours of MIPS 70um will provide the physical
measurements of the light distribution at the rest-frame ~8000A and
better estimates of the bolometric luminosity. Combining these
parameters together with the rich suite of spectral diagnostics from
the mid-IR spectra, we will {1} measure how common mergers are among
LIRGs and ULIRGs at 0.3z2.7, and establish if major mergers are the
drivers of z1 ULIRGs, as in the local Universe. {2} study the
co-evolution of star formation and blackhole accretion by
investigating the relations between the fraction of starburst/AGN
measured from mid-IR spectra vs. HST morphologies, L{bol} and z. {3}
obtain the current best estimates of the far-IR emission, thus L{bol}
for this sample, and establish if the relative contribution of
mid-to-far IR dust emission is correlated with morphology {resolved
vs. unresolved}.

WFPC2 11138

The Physics of the Jets of Powerful Radio Galaxies and Quasars

We propose to obtain HST polarimetry of the jets of the quasars
1150+497 and PKS 1136-135. Our goal is to solve the riddle of their
high-energy emission mechanism, and tackle issues such as particle
acceleration and jet dynamics. Our targets are the optically brightest
quasar jets, and they span the range of luminosities and beaming
parameters seen in these objects. Recent observations with Spitzer,
HST and Chandra have shed new light on the spectral morphology of
quasar jets, throwing wide open the question of the nature of their
optical and X-ray emission. Three mechanisms are possible, including
synchrotron emission as well as two Comptonization processes.
Polarimetry can uniquely determine which of these mechanisms operates
in the optical. We will compare the optical polarimetry to in- hand
radio polarimetry as well as in-hand and new Spitzer, HST and Chandra
imaging to gain new insights on the structure of these jets, as well
as particle acceleration mechanisms and jet dynamics.

WFPC2 11134

WFPC2 Tidal Tail Survey: Probing Star Cluster Formation on the Edge

The spectacular HST images of the interiors of merging galaxies such
as the Antennae and NGC 7252 have revealed rich and diverse
populations of star clusters created over the course of the
interaction. Intriguingly, our WFPC2 study of tidal tails in these and
other interacting pairs has shown that star cluster birth in the tails
does not follow a similarly straightforward evolution. In fact,
cluster formation in these relatively sparse environments is not
guaranteed -- only one of six tails in our initial study showed
evidence for a significant population of young star clusters. The tail
environment thus offers the opportunity to probe star cluster
formation on the edge of the physical parameter space {e.g., of
stellar and gas mass, density, and pressure} that permits it to occur.
We propose to significantly extend our pilot sample of optically
bright, gas-rich tidal tails by a factor of 4 in number to include a
more diverse population of tails, encompassing major and minor
mergers, gas-rich and gas-poor tails, as well as early, late, and
merged interaction stages. With 21 orbits of HST WFPC2 imaging in the
F606W and F814W filters, we can identify, roughly age-date, and
measure sizes of star clusters to determine what physical parameters
affect star cluster formation. WFPC2 imaging has been used effectively
in our initial study of four mergers, and it will be possible in this
program to reach similar limits of Mv=-8.5 for each of 16 more tails.
With the much larger sample we expect to isolate which factors, such
as merger stage, HI content, and merger mass ratio, drive the
formation of star clusters.

WFPC2 11130

AGNs with Intermediate-mass Black Holes: Testing the Black Hole-Bulge
Paradigm, Part II

The recent progress in the study of central black holes in galactic
nuclei has led to a general consensus that supermassive {10^6-10^9
solar mass} black holes are closely connected with the formation and
evolutionary history of large galaxies, especially their bulge
component. Two outstanding issues, however, remain unresolved. Can
central black holes form in the absence of a bulge? And does the mass
function of central black holes extend below 10^6 solar masses?
Intermediate-mass black holes {10^6 solar masses}, if they exist, may
offer important clues to the nature of the seeds of supermassive black
holes. Using the SDSS, our group has successfully uncovered a new
population of AGNs with intermediate-mass black holes that reside in
low-luminosity galaxies. However, very little is known about the
detailed morphologies or structural parameters of the host galaxies
themselves, including the crucial question of whether they have bulges
or not. Surprisingly, the majority of the targets of our Cycle 14
pilot program have structural properties similar to dwarf elliptical
galaxies. The statistics from this initial study, however, are really
too sparse to reach definitive conclusions on this important new class
of black holes. We wish to extend this study to a larger sample, by
using the Snapshot mode to obtain WFPC2 F814W images from a parent
sample of 175 AGNs with intermediate- mass black holes selected from
our final SDSS search. We are particularly keen to determine whether
the hosts contain bulges, and if so, how the fundamental plane
properties of the host depend on the mass of their central black
holes. We will also investigate the environment of this unique class
of AGNs.

WFPC2 11124

The Origin of QSO Absorption Lines from QSOs

We propose using WFPC2 to image the fields of 10 redshift z ~ 0.7
foreground {FG} QSOs which lie within ~29-151 kpc of the sightlines to
high-z background {BG} QSOs. A surprisingly high fraction of the BG
QSO spectra show strong MgII {2796,2803} absorption lines at precisely
the same redshifts as the FG QSOs. The high resolution capabilities of
WFPC2 are needed to understand the origin of these absorption systems,
in two ways. First, we wish to explore the FG QSO environment as close
as possible to the position of the BG QSO, to search for interloping
group or cluster galaxies which might be responsible for the
absorption, or irregularly shaped post-merger debris between the FG
and BG QSO which may indicate the presence of large amount of
disrupted gas along a sightline. Similarly, high resolution images are
needed to search for signs of tidal interactions between any galaxies
which might be found close to the FG QSO. Such features might provide
evidence of young merging events causing the start of QSO duty cycles
and producing outflows from the central AGN. Such winds may be
responsible for the observed absorption lines. Second, we seek to
measure the intrinsic parameters of the FG QSO host galaxy, such as
luminosity and morphology, to correlate with the properties of the
MgII absorption lines. We wish to observe each field through the F814W
filter, close to the rest- frame B-band of the FG QSO. These blue data
can reveal enhanced star formation regions close to the nucleus of the
host galaxy, which may be indicative of galaxy mergers with the FG QSO
host. The FG QSO environment offers quite a different set of phenomena
which might be responsible for MgII absorption, providing an important
comparison to studies of MgII absorption from regular field galaxies.

WFPC2 11122

Expanding PNe: Distances and Hydro Models

We propose to obtain repeat narrowband images of a sample of eighteen
planetary nebulae {PNe} which have HST/WFPC2 archival data spanning
time baselines of a decade. All of these targets have previous high
signal-to-noise WFPC2/PC observations and are sufficiently nearby to
have readily detectable expansion signatures after a few years. Our
main scientific objectives are {a} to determine precise distances to
these PNe based on their angular expansions, {b} to test detailed and
highly successful hydrodynamic models that predict nebular
morphologies and expansions for subsamples of round/elliptical and
axisymmetric PNe, and {c} to monitor the proper motions of nebular
microstructures in an effort to learn more about their physical nature
and formation mechanisms. The proposed observations will result in
high-precision distances to a healthy subsample of PNe, and from this
their expansion ages, luminosities, CSPN properties, and masses of
their ionized cores. With good distances and our hydro models, we will
be able to determine fundamental parameters {such as nebular and
central star masses, luminosity, age}. The same images allow us to
monitor the changing overall ionization state and to search for the
surprisingly non-homologous growth patterns to bright elliptical PNe
of the same sort seen by Balick & Hajian {2004} in NGC 6543.
Non-uniform growth is a sure sign of active pressure imbalances within
the nebula that require careful hydro models to understand.

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.

WFPC2 11103

A Snapshot Survey of The Most Massive Clusters of Galaxies

We propose the continuation of our highly successful SNAPshot survey
of a sample of 125 very X-ray luminous clusters in the redshift range
0.3-0.7. As demonstrated by the 25 snapshots obtained so far in
Cycle14 and Cycle15 these systems frequently exhibit strong
gravitational lensing as well as spectacular examples of violent
galaxy interactions. The proposed observations will provide important
constraints on the cluster mass distributions, the physical nature of
galaxy-galaxy and galaxy-gas interactions in cluster cores, and a set
of optically bright, lensed galaxies for further 8-10m spectroscopy.
All of our primary science goals require only the detection and
characterization of high-surface-brightness features and are thus
achievable even at the reduced sensitivity of WFPC2. Because of their
high redshift and thus compact angular scale our target clusters are
less adversely affected by the smaller field of view of WFPC2 than
more nearby systems. Acknowledging the broad community interest in
this sample we waive our data rights for these observations. Due to a
clerical error at STScI our approved Cycle15 SNAP program was barred
from execution for 3 months and only 6 observations have been
performed to date - reinstating this SNAP at Cycle16 priority is of
paramount importance to reach meaningful statistics.

WFPC2 11083

The Structure, Formation and Evolution of Galactic Cores and Nuclei

A surprising result has emerged from the ACS Virgo Cluster Survey
{ACSVCS}, a program to obtain ACS/WFC gz imaging for a large, unbiased
sample of 100 early-type galaxies in the Virgo Cluster. On
subarcsecond scales {i.e., 0.1"-1"}, the HST brightness profiles vary
systematically from the brightest giants {which have nearly constant
surface brightness cores} to the faintest dwarfs {which have compact
stellar nuclei}. Remarkably, the fraction of galaxy mass contributed
by the nuclei in the faint galaxies is identical to that contributed
by supermassive black holes in the bright galaxies {0.2%}. These
findings strongly suggest that a single mechanism is responsible for
both types of Central Massive Object: most likely internally or
externally modulated gas inflows that feed central black holes or lead
to the formation of "nuclear star clusters". Understanding the history
of gas accretion, star formation and chemical enrichment on
subarcsecond scales has thus emerged as the single most pressing
question in the study of nearby galactic nuclei, either active or
quiescent. We propose an ambitious HST program {199 orbits} that
constitutes the next, obvious step forward: high-resolution,
ultraviolet {WFPC2/F255W} and infrared {NIC1/F160W} imaging for the
complete ACSVCS sample. By capitalizing on HST's unique ability to
provide high-resolution images with a sharp and stable PSF at UV and
IR wavelengths, we will leverage the existing optical HST data to
obtain the most complete picture currently possible for the history of
star formation and chemical enrichment on these small scales. Equally
important, this program will lead to a significant improvement in the
measured structural parameters and density distributions for the
stellar nuclei and the underlying galaxies, and provide a sensitive
measure of "frosting" by young stars in the galaxy cores. By virtue of
its superb image quality and stable PSF, NICMOS is the sole instrument
capable of the IR observations proposed here. In the case of the WFPC2
observations, high-resolution UV imaging { 0.1"} is a capability
unique to HST, yet one that could be lost at any time.

WFPC2 11030

WFPC2 WF4 Temperature Reduction #3

In the fall of 2005, a serious anomaly was found in images from the
WF4 CCD in WFPC2. The WF4 CCD bias level appeared to have become
unstable, resulting in sporadic images with either low or zero bias
level. The severity and frequency of the problem was rapidly
increasing, making it possible that WF4 would soon become unusable if
no work-around were found. Examination of bias levels during periods
with frequent WFPC2 images showed low and zero bias episodes every 4
to 6 hours. This periodicity is driven by cycling of the WFPC2
Replacement Heater, with the bias anomalies occurring at the
temperature peaks. The other three CCDs {PC1, WF2, and WF3} appear to
be unaffected and continue to operate properly. Lowering the
Replacement Heater temperature set points by a few degrees C
effectively eliminates the WF4 anomaly. On 9 January 2006, the upper
set point of the WFPC2 Replacement Heater was reduced from 14.9C to
12.2C. On 20 February 2006, the upper set point was reduced from 12.2C
to 11.3C, and the lower set point was reduced from 10.9C to 10.0C.
These changes restored the WF4 CCD bias level; however, the bias level
has begun to trend downwards again, mimicking its behavior in late
2004 and early 2005. A third temperature reduction is planned for
March 2007. We will reduce the upper set point of the heater from
11.3C to 10.4C and the lower set point from 10.0C to 9.1C. The
observations described in this proposal will test the performance of
WFPC2 before and after this temperature reduction. Additional
temperature reductions may be needed in the future, depending on the
performance of WF4. Orbits: internal 26, external 1.

WFPC2 11029

WFPC2 CYCLE 15 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 15 decon proposal xxxx 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 11028

WFPC2 Cycle 15 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 8-14.

WFPC2 11027

Visible 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 conjunction with previous
internal and external flats to generate new pipeline superflats. These
Earth flats will complement the Earth flat data obtained during cycles
4-14.

WFPC2 11020

Cycle 15 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.

FLIGHT OPERATIONS SUMMARY:

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

HSTARS:

11203 - GSAcq (2,3,3) failed to RGA Hold (Gyro Control)

At 060/14:47:31 GSAcq (2,3,3) scheduled from 060/14:44:08 - 14:51:29
failed due to QF2STOPF and QSTOP flags on FGS-2. OBAD #1 RSS data was
unavailable due to LOS. OBAD #2 RSS = 16.84a-s. OBAD MAP RSS =
15.29a-s. Received 486 ESB 1808 (x2) TxG Sanity Check Failed at AOS
(060/14:43:00). At 14:47:15 mnemonic F2SSCEA flagged Red High
EV=10.16, RV=255, EU UL=10 / LL= -10.

11204 - GSAcq (2,1,2) results in Fine Lock Backup (2,0,2)

At AOS (060/18:10:15) GSAcq (2,1,2) scheduled from
060/17:47:29-17:54:48 resulted in Fine Lock Backup (2,0,2) due to
QF1STOPF and QSTOP flags on FGS-1. Due to LOS, Pre-acquisition OBAD 1
& 2 data will be unavailable until the next scheduled engineering data
dump at 061/13:09:29. Post-acquisition OBAD MAP RSS = 13.35 a-s.

COMPLETED OPS REQUEST: (None)

COMPLETED OPS NOTES: (None)

********************** SCHEDULED***** SUCCESSFUL

FGS GSacq************** 26**************** 25
FGS REacq************** 16**************** 16
OBAD with Maneuver **** 84**************** 84

SIGNIFICANT EVENTS: (None)


 




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