Daily Report #4352

Notice: For the foreseeable future, the daily reports may contain apparent
discrepancies between some proposal descriptions and the listed instrument
usage. This is due to the conversion of previously approved ACS WFC or HRC
observations into WFPC2, or NICMOS observations subsequent to the loss of
ACS CCD science capability in late January.


HUBBLE SPACE TELESCOPE - Continuing to collect World Class Science

DAILY REPORT # 4352

PERIOD COVERED: UT April 30, 2007 (DOY 120)

OBSERVATIONS SCHEDULED

ACS/SBC 10864

Mapping the Gaseous Content of Protoplanetary and Young Planetary Systems
with ACS

One of the key problems in planetary system formation is understanding how
rapidly, and over what time interval Jovian planets can form. Dust in the
protoplanetary disk is critical in planetesimal formation, but it is the gas
which produces giant planets, and which is essential for their migration.
However, compared to data on the circumstellar dust, information on the gas
component is sparse, especially in the planet-formation zone. This severely
limits our ability to put observational constraints on giant planet
formation, except to note that the process must be largely complete by 12
Myr, given the paucity of Herbig Ae or classical T Tauri stars older than
10-12 Myr. In the FUV, photo-excited molecular hydrogen transitions have the
requisite contrast to the stellar photosphere, accretion shock, and
reflection nebulosity, and can be traced 50-100 AU from the exciting stars
in both envelopes and outflow cavities and protoplanetary disks. Central
disk cavities, an expected consequence of planet formation, larger than 0.1"
are directly detectable in HST FUV spectra, while smaller cavities may be
detected by comparison with protoplanetary disks which are still accreting
onto their stars. We propose augmenting existing HST coronagraphic imagery
of 6 Herbig Fe and T Tauri disks with ACS Solar-Blind Channel Lyman alpha
imagery and slitless spectroscopy simultaneously sampling the disk in
molecular hydrogen and small-grain reflection nebulosity. These data will be
used to quantify the amount of vertical stratification in these disks, to
map the mass-loss geometry from the star, and to determine whether removal
of molecular material preceeds, lags, or is contemporary with clearing of
the dust.

WFPC2 11024

WFPC2 CYCLE 15 INTERNAL MONITOR

This calibration proposal is the Cycle 15 routine internal monitor for
WFPC2, to be run weekly to monitor the health of the cameras. A variety of
internal exposures are obtained in order to provide a monitor of the
integrity of the CCD camera electronics in both bays {both gain 7 and gain
15 -- to test stability of gains and bias levels}, a test for quantum
efficiency in the CCDs, and a monitor for possible buildup of contaminants
on the CCD windows. These also provide raw data for generating annual
super-bias reference files for the calibration pipeline.

NIC1 10889

The Nature of the Halos and Thick Disks of Spiral Galaxies

We propose to resolve the extra-planar stellar populations of the thick
disks and halos of seven nearby, massive, edge-on galaxies using ACS,
NICMOS, and WFPC2 in parallel. These observations will provide accurate star
counts and color-magnitude diagrams 1.5 magnitudes below the tip of the Red
Giant Branch sampled along the two principal axes and one intermediate axis
of each galaxy. We will measure the metallicity distribution functions and
stellar density profiles from star counts down to very low average surface
brightnesses, equivalent to ~32 V-mag per square arcsec. These observations
will provide the definitive HST study of extra-planar stellar populations of
spiral galaxies. Our targets cover a range in galaxy mass, luminosity, and
morphology and as function of these galaxy properties we will provide: - The
first systematic study of the radial and isophotal shapes of the diffuse
stellar halos of spiral galaxies - The most detailed comparative study to
date of thick disk morphologies and stellar populations - A comprehensive
analysis of halo and thick disk metallicity distributions as a function of
galaxy type and position within the galaxy. - A sensitive search for tidal
streams - The first opportunity to directly relate globular cluster systems
to their field stellar population We will use these fossil records of the
galaxy assembly process preserved in the old stellar populations to test
halo and thick disk formation models within the hierarchical galaxy
formation scheme. We will test LambdaCDM predictions on sub-galactic scales,
where it is difficult to test using CMB and galaxy redshift surveys, and
where it faces its most serious difficulties.

NIC1/NIC2/NIC3 8794

NICMOS Post-SAA calibration - CR Persistence Part 5

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.

NIC3 11080

Exploring the Scaling Laws of Star Formation

As a variety of surveys of the local and distant Universe are approaching a
full census of galaxy populations, our attention needs to turn towards
understanding and quantifying the physical mechanisms that trigger and
regulate the large-scale star formation rates {SFRs} in galaxies.

WFPC2 11023

WFPC2 CYCLE 15 Standard Darks - part 1

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

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 any
time.

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:

18055-0 - Halt and Restart of the KF for Clock Rollover
18054-0 - Preview KF Sun Vector Data via Telemetry Diags

COMPLETED OPS NOTES: (None)

SCHEDULED SUCCESSFUL

FGS GSacq 08 08
FGS REacq 06 06
OBAD with Maneuver 28 28

SIGNIFICANT EVENTS: (None)