Daily Report #4564

HUBBLE SPACE TELESCOPE - Continuing to collect World Class Science

DAILY REPORT***** # 4564

PERIOD COVERED: UT March 10, 2008 (DOY 070)

OBSERVATIONS SCHEDULED

NIC1/NIC2/NIC3 8795

NICMOS Post-SAA calibration - CR Persistence Part 6

A new procedure proposed to alleviate the CR-persistence problem of
NICMOS. Dark frames will be obtained immediately upon exiting the SAA
contour 23, and every time a NICMOS exposure is scheduled within 50
minutes of coming out of the SAA. The darks will be obtained in
parallel in all three NICMOS Cameras. The POST-SAA darks will be
non-standard reference files available to users with a USEAFTER
date/time mark. The keyword 'USEAFTER=date/time' will also be added to
the header of each POST-SAA DARK frame. The keyword must be populated
with the time, in addition to the date, because HST crosses the SAA ~8
times per day so each POST-SAA DARK will need to have the appropriate
time specified, for users to identify the ones they need. Both the raw
and processed images will be archived as POST-SAA DARKSs. Generally we
expect that all NICMOS science/calibration observations started within
50 minutes of leaving an SAA will need such maps to remove the CR
persistence from the science images. Each observation will need its
own CRMAP, as different SAA passages leave different imprints on the
NICMOS detectors.

NIC2 11148

High Contrast Imaging of Dusty White Dwarfs

For the past 18 years, only one white dwarf with a circumstellar dust
disk was known to exist. In the last two years, six new disks have
been discovered. Since all material inwards of a few AU should be
scoured clean during post main sequence evolution, the primary
explanation is the presence of a planetary system that is perturbing
relic planetesimals into the tidal disruption radius of the white
dwarf. Dusty disks around white dwarfs should be markers for planets
and we propose to use high contrast imaging to search for faint
companions down to 6 M_$J$ that may be feeding the disks. White dwarfs
are uniquely suited for planet searches, where the planet/white dwarf
contrast is less than for main sequence stars.

NIC2 11155

Dust Grain Evolution in Herbig Ae Stars: NICMOS Coronagraphic Imaging
and Polarimetry

We propose to take advantage of the sensitive coronagraphic
capabilities of NICMOS to obtain multiwavelength coronagraphic imaging
and polarimetry of primordial dust disks around young
intermediate-mass stars {Herbig Ae stars}, in order to advance our
understanding of how dust grains are assembled into larger bodies.
Because the polarization of scattered light is strongly dependent on
scattering particle size and composition, coronagraphic imaging
polarimetry with NICMOS provides a uniquely powerful tool for
measuring grain properties in spatially resolved circumstellar disks.
It is widely believed that planets form via the gradual accretion of
planetesimals in gas-rich, dusty circumstellar disks, but the
connection between this suspected process and the circumstellar disks
that we can now observe around other stars remains very uncertain. Our
proposed observations, together with powerful 3-D radiative transfer
codes, will enable us to quantitatively determine dust grain
properties as a function of location within disks, and thus to test
whether dust grains around young stars are in fact growing in size
during the putative planet-formation epoch. HST imaging polarimetry of
Herbig Ae stars will complement and extend existing polarimetric
studies of disks around lower-mass T Tauri stars and debris disks
around older main-sequence stars. When combined with these previous
studies, the proposed research will help us establish the influence of
stellar mass on the growth of dust grains into larger planetesimals,
and ultimately to planets. Our results will also let us calibrate
models of the thermal emission from these disks, a critical need for
validating the properties of more distant disks inferred on the basis
of spectral information alone.

NIC2 11164

Molecular Hydrogen Disks Around T Tauri Stars

We propose to measure the properties of planetary system-sized disks
around Sun- like, pre-main sequence stars by imaging the inner parts
of these disks for the first time in gaseous emission from their most
dominant constituent, molecular hydrogen gas. Specifically, we will
use the F212N filter and NICMOS to determine the spatial distribution
of ro-vibrational H2 emission from protoplanetary disks around
selected classical and weak-lined T Tauri stars. The target stars are
among those detected by members of this team through high resolution,
ground-based infrared spectroscopy. The spectra reveal H2 emission at
the rest velocities of the stars and at positions spatially coincident
with the stars at the spatial resolution of the spectroscopic data.
This imaging experiment, which is impossible to do using ground- based
facilities, is possible using the NICMOS camera aboard the HST because
the point spread function of this system is extremely stable and can
be measured to a very high accuracy. This experiment is an important
test of the interpretation that the 2.122 micron H2 line emission seen
toward T Tauri stars is produced at distances of 10 to 30 AU from the
stars, the region in which giant planets are expected to form around
these stars. These observations will contribute toward developing a
better understanding of the process, likelihood, and timescale for the
formation of planets around Sun-like stars.

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.

WFPC2 11022

WFPC2 Cycle 15 Decontaminations and Associated Observations

This proposal is for the WFPC2 decons. Also included are instrument
monitors tied to decons: photometric stability check, focus monitor,
pre- and post-decon internals {bias, intflats, kspots, & darks}, UV
throughput check, VISFLAT sweep, and internal UV flat check.

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 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 11169

Collisions in the Kuiper belt

For most of the 15 year history of observations of Kuiper belt
objects, it has been speculated that impacts must have played a major
role in shaping the physical and chemical characteristics of these
objects, yet little direct evidence of the effects of such impacts has
been seen. The past 18 months, however, have seen an explosion of
major new discoveries giving some of the first insights into the
influence of this critical process. From a diversity of observations
we have been led to the hypotheses that: {1} satellite-forming impacts
must have been common in the Kuiper belt; {2} such impacts led to
significant chemical modification; and {3} the outcomes of these
impacts are sufficiently predictable that we can now find and study
these impact-derived systems by the chemical and physical attributes
of both the satellites and the primaries. If our picture is correct,
we now have in hand for the first time a set of incredibly powerful
tools to study the frequency and outcome of collisions in the outer
solar system. Here we propose three linked projects that would answer
questions critical to the multiple prongs of our hypothesis. In these
projects we will study the chemical effects of collisions through
spectrophotometric observations of collisionally formed satellites and
through the search for additional satellites around primaries with
potential impact signatures, and we will study the physical effects of
impacts through the examination of tidal evolution in proposed impact
systems. The intensive HST program that we propose here will allow us
to fully test our new hypotheses and will provide the ability to
obtain the first extensive insights into outer solar system impact
processes.

WFPC2 11339

A deep observation of NGC4261: understanding its unique X-ray source
population, gas morphology, and jet properties

The nearby early-type galaxy NGC4261 reveals strikingly asymmetric
distributions of X-ray sources as seen with Chandra, and globular
clusters (GC) as seen in the optical band. To address the link between
these populations based on their spatial correlation, luminosity
function and spectral properties, and to investigate the possibility
that this effect is due to the galaxy's merger history, we propose a
100ksec Chandra ACIS-S3 exposure, which will detect X-ray sources down
to typical LMXB luminosities (Lx~5E37 erg/s), and HST-WFPC2
observations to obtain a deep census of the GC population over the
whole galaxy. These data will also allow a detailed study of its
complex gaseous component, and provide information on the unique
two-sided X-ray jet.

FLIGHT OPERATIONS SUMMARY:

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

HSTARS: (None)

COMPLETED OPS REQUEST: (None)

COMPLETED OPS NOTES: (None)

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

FGS GSacq************** 13**************** 13
FGS REacq************** 02**************** 02
OBAD with Maneuver **** 30**************** 30

SIGNIFICANT EVENTS: (None)