HUBBLE
SPACE TELESCOPE - Continuing to collect World Class Science
DAILY
REPORT # 4573
PERIOD
COVERED: UT March 21,22,23, 2008 (DOY 081,082,083)
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.
NIC3
11334
NICMOS
Cycle 16 Spectrophotometry
Observation
of the three primary WD flux standards must be repeated to
refine
the NICMOS absolute calibration and monitor for sensitivity
degradation.
So far, NICMOS grism spectrophotometry is available for
only
~16 stars with good STIS spectra at shorter wavelengths. There are
more
in the HST CALSPEC standard star data base with good STIS spectra
that
would also become precise IR standards with NICMOS absolute SED
measurements.
Monitoring the crucial three very red stars (M, L, T) for
variability
and better S/N in the IR. Apparent variability was
discovered
at shorter wavelengths during the ACS cross-calibration work
that
revealed a ~2% discrepancy of the cool star fluxes with respect to
the
hot primary WD standards. About a third of these stars are bright
enough
to do in one orbit, the rest require 2 orbits.
WFPC2
11233
Multiple
Generations of Stars in Massive Galactic Globular Clusters
This
is a follow-up to recent HST imaging of NGC 2808, which discovered
that
its main sequence is triple, with three well-separated parallel
branches
{Fig.~1}. Along with the double MS of Omega Centauri, this
challenges
the long-held paradigm that globular clusters are simple,
single
stellar populations. The cause of this main sequence multiplicity
in
both clusters is likely to be differences in helium abundance, which
could
play a fundamental role in the understanding of stellar
populations.
We propose to image seven more of the most massive globular
clusters,
to examine their main sequences for indications of splitting.
NIC2
11219
Active
Galactic Nuclei in nearby galaxies: a new view of the origin of
the
radio-loud radio-quiet dichotomy?
Using
archival HST and Chandra observations of 34 nearby early-type
galaxies
{drawn from a complete radio selected sample} we have found
evidence
that the radio-loud/radio-quiet dichotomy is directly connected
to
the structure of the inner regions of their host galaxies in the
following
sense: [1] Radio-loud AGN are associated with galaxies with
shallow
cores in their light profiles [2] Radio-quiet AGN are only
hosted
by galaxies with steep cusps. Since the brightness profile is
determined
by the galaxy's evolution, through its merger history, our
results
suggest that the same process sets the AGN flavour. This
provides
us with a novel tool to explore the co-evolution of galaxies
and
supermassive black holes, and it opens a new path to understand the
origin
of the radio-loud/radio-quiet AGN dichotomy. Currently our
analysis
is statistically incomplete as the brightness profile is not
available
for 82 of the 116 targets. Most galaxies were not observed
with
HST, while in some cases the study is obstructed by the presence of
dust
features. We here propose to perform an infrared NICMOS snapshot
survey
of these 82 galaxies. This will enable us to i} test the reality
of
the dichotomic behaviour in a substantially larger sample; ii} extend
the
comparison between radio-loud and radio-quiet AGN to a larger range
of
luminosities.
FGS
11213
Distances
to Eclipsing M Dwarf Binaries
We
propose HST FGS observations to measure accurate distances of 5
nearby
M dwarf eclipsing binary systems, from which model-independent
luminosities
can be calculated. These objects have either poor or no
existing
parallax measurements. FGS parallax determinations for these
systems,
with their existing dynamic masses determined to better than
0.5%,
would serve as model-independent anchor points for the low-mass
end
of the mass-luminosity diagram.
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.
WFPC2
11207
Star
Formation in the Perseus Cluster Cooling Flow
We
propose to obtain high resolution, UV/optical imaging of the
"accretion
populations" in the massive cooling flow of the Perseus
cluster
of galaxies. New GALEX observations show that the dominant
galaxy
in this nearby cluster, NGC 1275, has an extended network of
UV-bright
populations apparently formed recently from the intracluster
gas.
Cluster cooling flows are the most prominent of the environments
where
we can readily observe the cycle of gas accretion, star formation,
and
feedback from active nuclei that is thought to play a central role
in
the formation and evolution of galaxies. Because they can be readily
age-dated,
the accretion populations help to trace the sequence of
exchange
of material between galaxies and the intracluster medium. The
ACS/SBC
and WFPC2/PC cameras offer the highest spatial resolution and
best
panchromatic performance available to map the spatial and age
distribution
of the accretion populations and their relationship to
radio-emitting
plasma and the hot intracluster gas.
WFPC2
11202
The
Structure of Early-type Galaxies: 0.1-100 Effective Radii
The
structure, formation and evolution of early-type galaxies is still
largely
an open problem in cosmology: how does the Universe evolve from
large
linear scales dominated by dark matter to the highly non-linear
scales
of galaxies, where baryons and dark matter both play important,
interacting,
roles? To understand the complex physical processes
involved
in their formation scenario, and why they have the tight
scaling
relations that we observe today {e.g. the Fundamental Plane}, it
is
critically important not only to understand their stellar structure,
but
also their dark-matter distribution from the smallest to the largest
scales.
Over the last three years the SLACS collaboration has developed
a
toolbox to tackle these issues in a unique and encompassing way by
combining
new non-parametric strong lensing techniques, stellar
dynamics,
and most recently weak gravitational lensing, with
high-quality
Hubble Space Telescope imaging and VLT/Keck spectroscopic
data
of early-type lens systems. This allows us to break degeneracies
that
are inherent to each of these techniques separately and probe the
mass
structure of early-type galaxies from 0.1 to 100 effective radii.
The
large dynamic range to which lensing is sensitive allows us both to
probe
the clumpy substructure of these galaxies, as well as their
low-density
outer haloes. These methods have convincingly been
demonstrated,
by our team, using smaller pilot-samples of SLACS lens
systems
with HST data. In this proposal, we request observing time with
WFPC2
and NICMOS to observe 53 strong lens systems from SLACS, to obtain
complete
multi-color imaging for each system. This would bring the total
number
of SLACS lens systems to 87 with completed HST imaging and
effectively
doubles the known number of galaxy-scale strong lenses. The
deep
HST images enable us to fully exploit our new techniques, beat down
low-number
statistics, and probe the structure and evolution of
early-type
galaxies, not only with a uniform data-set an order of
magnitude
larger than what is available now, but also with a fully
coherent
and self-consistent methodological approach!
WFPC2
11198
Pure
Parallel Imaging in the NDWFS Bootes Field
The
NOAO Deep-Wide Field Survey {NDWFS} Bootes field is the target of
one
of the most extensive multiwavelength campaigns in astronomy. In
addition
to ground-based optical and near-infrared imaging, deep radio
mapping,
and extensive spectroscopy, this entire region has been imaged
by
the Chandra, Spitzer {IRAC and MIPS}, and GALEX missions. Robust
photometric
redshifts {calibrated using over 20,000 spectroscopic
redshifts}
exist for all sources brighter than R=24.5 or than 13 uJy at
4.5
microns. To enhance the value of this data set, we propose pure
parallel
observations for all approved Cycle 16 programs in this region
that
lack coordinated parallel observations. The primary aim of this
program
will be to provide a database useful for the broad range of
science
programs underway in this region.
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.
WFPC2
11184
Imaging
the Shock Precursor in Tycho's SNR
Cosmic
ray acceleration in supernova remnant shocks requires shock
precursors
where particles are trapped by plasma turbulence. The
precursors
also heat and compress the upstream gas, producing H alpha
emission
and affecting line profiles. We propose to image the brightest
non-radiative
shock in Tycho's SNR to measure the brightness and width
of
the precursor. These measurements will constrain 2 key parameters in
cosmic
ray acceleration models, and they will improve the accuracy of
shock
speed and electron-ion equilibration derived from H alpha
profiles.
WFPC2
11178
Probing
Solar System History with Orbits, Masses, and Colors of
Transneptunian
Binaries
The
recent discovery of numerous transneptunian binaries {TNBs} opens a
window
into dynamical conditions in the protoplanetary disk where they
formed
as well as the history of subsequent events which sculpted the
outer
Solar System and emplaced them onto their present day heliocentric
orbits.
To date, at least 47 TNBs have been discovered, but only about a
dozen
have had their mutual orbits and separate colors determined,
frustrating
their use to investigate numerous important scientific
questions.
The current shortage of data especially cripples scientific
investigations
requiring statistical comparisons among the ensemble
characteristics.
We propose to obtain sufficient astrometry and
photometry
of 23 TNBs to compute their mutual orbits and system masses
and
to determine separate primary and secondary colors, roughly tripling
the
sample for which this information is known, as well as extending it
to
include systems of two near-equal size bodies. To make the most
efficient
possible use of HST, we will use a
optimally
schedule our observations.
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.
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
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
11128
Time
Scales Of Bulge Formation In Nearby Galaxies
Traditionally,
bulges are thought to fit well into galaxy formation
models
of hierarchical merging. However, it is now becoming well
established
that many bulges formed through internal, secular evolution
of
the disk rather than through mergers. We call these objects
pseudobulges.
Much is still unknown about pseudobulges, the most
pressing
questions being: How, exactly, do they build up their mass? How
long
does it take? And, how many exist? We are after an answer to these
questions.
If pseudobulges form and evolve over longer periods than the
time
between mergers, then a significant population of pseudobulges is
hard
to explain within current galaxy formation theories. A pseudobulge
indicates
that a galaxy has most likely not undergone a major merger
since
the formation of the disk. The ages of pseudobulges give us an
estimate
for the time scale of this quiescent evolution. We propose to
use
24 orbits of HST time to complete UBVIH imaging on a sample of 33
nearby
galaxies that we have observed with Spitzer in the mid-IR. These
data
will be used to measure spatially resolved stellar population
parameters
{mean stellar age, metallicity, and star formation history};
comparing
ages to star formation rates allows us to accurately constrain
the
time scale of pseudobulge formation. Our sample of bulges includes
both
pseudo- and classical bulges, and evenly samples barred and
unbarred
galaxies. Most of our sample is imaged, 13 have complete UBVIH
coverage;
we merely ask to complete missing observations so that we may
construct
a uniform sample for studying bulge formation. We also wish to
compare
the stellar population parameters to a variety of bulge and
global
galaxy properties including star formation rates, dynamics,
internal
bulge morphology, structure from bulge-disk decompositions, and
gas
content. Much of this data set is already or is being assembled.
This
will allow us to derive methods of pseudobulge identification that
can
be used to accurately count pseudobulges in large surveys. Aside
from
our own science goals, we will present this broad set of data to
the
community. Thus, we waive proprietary periods for all observations.
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
11120
A
Paschen-Alpha Study of Massive Stars and the ISM in the Galactic
Center
The
Galactic center (GC) is a unique site for a detailed study of a
multitude
of complex astrophysical phenomena, which may be common to
nuclear
regions of many galaxies. Observable at resolutions
unapproachable
in other galaxies, the GC provides an unparalleled
opportunity
to improve our understanding of the interrelationships of
massive
stars, young stellar clusters, warm and hot ionized gases,
molecular
clouds, large scale magnetic fields, and black holes. We
propose
the first large-scale hydrogen Paschen alpha line survey of the
GC
using NICMOS on the Hubble Space Telescope. This survey will lead to
a
high resolution and high sensitivity map of the Paschen alpha line
emission
in addition to a map of foreground extinction, made by
comparing
Paschen alpha to radio emission. This survey of the inner 75
pc
of the Galaxy will provide an unprecedented and complete search for
sites
of massive star formation. In particular, we will be able to (1)
uncover
the distribution of young massive stars in this region, (2)
locate
the surfaces of adjacent molecular clouds, (3) determine
important
physical parameters of the ionized gas, (4) identify compact
and
ultra-compact HII regions throughout the GC. When combined with
existing
Chandra and Spitzer surveys as well as a wealth of other
multi-wavelength
observations, the results will allow us to address such
questions
as where and how massive stars form, how stellar clusters are
disrupted,
how massive stars shape and heat the surrounding medium, and
how
various phases of this medium are interspersed.
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
10905
The
Dynamic State of the Dwarf Galaxy Rich Canes Venatici I Region
With
accurate distances, the nearest groups of galaxies can be resolved
in
3 dimensions and the radial component of the motions of galaxies due
to
local density perturbations can be distinguished from cosmological
expansion
components. Currently, with the ACS, galaxy distances within 8
Mpc
can be measured effectively and efficiently by detecting the tip of
the
red giant branch {TRGB}. Of four principal groups at high galactic
latitude
in this domain, the Canes Venatici I Group {a} is the least
studied,
{b} is the most populated, though overwhelmingly by dwarf
galaxies,
and {c} is likely the least dynamically evolved. It is
speculated
that galaxies in low mass groups may fail to retain baryons
as
effectively as those in high mass groups, resulting in significantly
higher
mass-to-light ratios. The CVn I Group is suspected to lie in the
mass
regime where the speculated astrophysical processes that affect
baryon
retention are becoming important.
WFPC2
10896
An
Efficient ACS Coronagraphic Survey for Debris Disks around Nearby
Stars
We
propose to finish our Cycle 11 optical survey for nearby debris disks
using
the ACS/HRC coronagraph. Out of 43 orbits originally proposed for
the
survey, 23 orbits were allocated, leading to a survey of 22 stars,
from
which two new debris disks were imaged for the first time. Our
analysis
of the initial survey gives an empirical estimate for the
detection
rate of debris disks relative to heliocentric distance and
dust
optical depth. Our target list for Cycle 15 is now optimized to
yield
more frequent disk detections. Likewise our observing strategy is
improved
to maximize sensitivity per telescope orbit allocated.
Therefore
we present the most efficient survey possible. The scientific
motivation
is to obtain scattered light images of previously unresolved
debris
disks to determine their viewing geometry and physical
architecture,
both of which may characterize the underlying planetary
system.
We choose 25 debris disk targets for which we predict a
detection
rate of 25% ? 5%. Four targets have extrasolar planets from
which
the viewing geometry revealed by a disk detection will resolve the
v
sin{i} ambiguity in the planet masses. These targets present the
remarkable
opportunity of finally seeing a debris disk in system with
known
planets.
FLIGHT
OPERATIONS SUMMARY:
Significant
Spacecraft Anomalies: (The following are preliminary reports
of
potential non-nominal performance that will be investigated.)
HSTARS:
11228
- GSAcq (1,2,2) failed to RGA Hold (Gyro Hold)
At 082/00:15:25, GSAcq (1,2,2) scheduled at 082/00:11:16-00:18:32
failed
to RGA Hold (Gyro Control) due QSTOP flag on FGS 1. Received
QF1STOPF &
QSTOP stop flags on FGS1. No 486 STB messages noted.
Pre-acquisition
OBAD #1 RSS value = 2128.48 arc-seconds. Pre acquisition OBAD #2
RSS
value = 9.03 arc-seconds. Post-acquisition OBAD MAP was not
scheduled.
REAcq (1,2,2) at 082/01:48:35 was successful.
11229
- REacq(2,3,3) Failed to RGA Hold
During LOS REacq(2,3,3) scheduled at 084/06:09:24 failed to RGA
Hold. At
AOS no flags were set. OBAD1 showed errors of V1= -292.59,
V2=-444.58,
V3 =139.19 and RSS= 550.13. OBAS2 showed errors of V1=79.07,
V2=68.78,
V3=30.91 and RSS = 109.26 .
11230
- REacq(2,3,3) Failed to Gyro Hold
REacq(2,3,3) scheduled at 084/07:45:16 failed at 07:50:08 due to
search
radius limit exceeded on FGS 2. OBAD2 showed errors of V1=3.39,
V2=0.28,
V3=-0.40, and RSS=3.42.
COMPLETED
OPS REQUEST: (None)
COMPLETED
OPS NOTES: (None)
SCHEDULED
SUCCESSFUL
FGS
GSacq
26
25
FGS
REacq
17
15
OBAD
with Maneuver
76
76
SIGNIFICANT
EVENTS: (None)