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 i
mages.
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
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 {R>26} 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
4.5<z<6.5,
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
0.3<z<2.7
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 {0.3<z<2.7}. 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 0.3<z<2.7, and establish if major mergers are the drivers
of
z>1 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)