Daily #4056

HUBBLE SPACE TELESCOPE - Continuing to collect World Class Science

DAILY REPORT #4056

PERIOD COVERED: UT February 22, 2006 (DOY 053)

OBSERVATIONS SCHEDULED

ACS/HRC 10516

Host Galaxies of Reverberation-Mapped AGNs

We propose to obtain unsaturated ACS high-resolution images of four
reverberation-mapped active galactic nuclei in order to remove the
point-like nuclear light from each image, thus yielding a
"nucleus-free" image of the host galaxy. This will allow investigation
of host galaxy properties: our particular interest is determination of
the host-galaxy starlight contribution to the reverberation-mapping
observations. This is necessary {1} for accurate determination of the
relationship between the AGN nuclear continuum flux and the size of
the broad Balmer-line emitting regions of AGNs, which is important
because this relationship is used in estimating black hole masses for
large samples of QSOs, and {2} for accurate determination of the
bolometric luminosity of the AGN proper. In a Cycle 12 SNAP program,
we obtained images of 14 of the 36 reverberation-mapped AGNs for this
purpose. This additional request is to complete this program through
observations of the four important remaining sources.

ACS/HRC 10623

HST Optical Snapshot Survey of Intermediate Redshift Ultraluminous
Infrared Galaxies

Ultraluminous infrared galaxies {ULIGs} are commonly believed to be a
transitory phase in the evolution of disk galaxy mergers into QSOs.
However, a recently reported discrepancy between the morphological and
structural properties of z 0.13 ULIGs and z = 0.12-0.25 QSOs with
M{V} -23.5 has cast doubt on their evolutionary connection. We
propose an ACS snapshot survey of a sample of 39 ULIGs with z =
0.35-1.0. These galaxies are the best suited for comparison with
luminous z=0.12-0.25 QSOs because {1} they are at larger lookback
times than local ULIGs, and thus are likely representative of the
systems that evolve into lower redshift luminous QSOs, {2} they have
luminosities comparable to luminous QSOs and, {3} they are selected in
a manner that biases the sample towards harboring imbedded AGN, and
thus are the most likely precursors to optical QSOs. High resolution
HST ACS images will allow a determination of galaxy morphology and
reveal the presence of bright AGN. The 2-D profile of each galaxy will
be modeled using GALFIT, with the AGN comprising one component of the
fit where applicable to better characterize the underlying galaxy.
Fundamental parameters {effective radius and surface brightness, and
F814W-band magnitude} of the underlying galaxy will thus be measured
and compared with the host galaxies of the luminous QSO sample. This
imaging campaign will consume a modest amount of HST time, but will
provide for the first time a statistically significant view of ULIGs
at look-back times of 30-65% the age of the universe, and sufficient
resolution and sensitivity to conduct a meaningful comparison with
z=0.12-0.25 QSOs, as well as with local {z 0.3} IRAS-detected and
distant {z 2} SCUBA-detected ULIGs.

ACS/HRC/WFC 10729

ACS CCDs daily monitor

This program consists of a set of basic tests to monitor, the read
noise, the development of hot pixels and test for any source of noise
in ACS CCD detectors. The files, biases and dark will be used to
create reference files for science calibration. This programme will be
for the entire lifetime of ACS. Changes from cycle 13:- The default
gain for WFC is 2 e-/DN. As before bias frames will be collected for
both gain 1 and gain 2. Dark frames are acquired using the default
gain {2}. This program cover the period Oct, 2 2005- May, 29-2006. The
second half of the program has a different proposal number: 10758.

ACS/WFC 10574

Witnessing Galaxy Transformation in Galaxy Groups at z 1

The recent discover of five galaxy groups in the Lynx supercluster
region offers us the exciting opportunity to observe for the first
time groups in the process of collapsing into a merging pair of
clusters at z 1. Our current picture of structure formation suggests
that substantial evolution of galaxy properties can occur in groups
and filaments well before they enter the environs of massive clusters.
However, neither current theoretical models nor observations give us a
complete understanding of the relative importance of the different
physical processes that control the structural and spectral
transformations that occur prior to, during, and after infall into a
dense environment. We propose direct observation of these newly
discovered dynamically young structures in the Lynx region, in order
to provide a critical benchmark in testing not only whether galaxy
evolution occurs mostly prior to entry into the densest regions but
will also constrain the relative importance of initial conditions in
determining the fate of galaxy systems. Our analysis of these proposed
ACS measurements will be complemented with an unique dataset we have
already in the optical, infrared, mid-infrared, and X-ray.

WFPC2 10608

Probing the star formation law in the extreme outer limits of M83, a
prototypical XUV-disk galaxy

The Galaxy Evolution Explorer {GALEX} has discovered a new sub-class
of spiral galaxy, which we refer to as extended UV-disk {XUV-disk}
galaxies. They are distinguished by conspicuous UV-bright star
clusters located at galactocentric radii extending to many times the
optical {R25} extent, and appear to represent a population of spiral
galaxies still actively building, or augmenting, their stellar disk.
However, XUV-disks pose a mystery in the form of a relative lack of
HII regions {traced by H-alpha emission} associated with outer disk,
UV-bright stellar clusters. M83 is an XUV-disk prototype and the focus
of this proposal. It has an H-alpha surface brightness profile
characterized by a steep decline at the radius beyond which the
gaseous disk is thought to become dynamically stable {against collapse
and ensuing star formation}, but GALEX UV profiles show no "edge" at
this location. Our HST study of M83 aims to resolve this puzzling
discrepancy, confirmed in several XUV-disks, by searching for
Lyman-continuum producing O stars that are either absent or present
without nebulosity. HST provides the only means of resolving
individual massive stars in the FUV band at M83's distance. Without
HST, we lose the critical ability to photometrically classify O and B
stars. Our multiwavelength observations will also constrain the
history of star formation in the outer disk over Gyr timescales by
characterizing the evolved stellar population, both using resolved
giants and color analysis of the diffuse background.

WFPC2 10779

WFPC2 WF4 Temperature Reduction Test #2

A serious anomaly has been found in images from the WF4 CCD in WFPC2.
The WF4 CCD bias level appears to have become unstable, resulting in
sporadic images with either low or zero bias level. The severity and
frequency of the problem is rapidly increasing, and it is possible
that WF4 will soon become unusable if no work-around is found. The
other three CCDs {PC1, WF2, and WF3} appear to be unaffected and
continue to operate properly. This is a second test to further reduce
temperatures. Orbits: internal 26, external 1

FLIGHT OPERATIONS SUMMARY:

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

HSTARS:

10144 - GSAcq(1,3,1) requires multiple attempts to achieve CTDV @ 049/2346z

Review of PTAS data revealed that GSAcq(1,3,1), scheduled for 2006/049
23:45:36 required three entries into CT before achieving CT-DV.


COMPLETED OPS REQUEST:
17649-0 - Genslew for Proposal 10599 - Slot#7 @053/1708z
17650-0 - Genslew for Proposal 10599 - Slot#8 @053/1710z
17651-0 - Genslew for Proposal 10599 - Slot#9 @053/1711z
17652-0 - Genslew for Proposal 10599 - Slot#11 @053/1712z
17653-0 - Genslew for Proposal 10599 - Slot#10 @053/1714z
17654-0 - Genslew for Proposal 10599 - Slot#14 @053/1715z
17655-0 - Genslew for Proposal 10599 - Slot#13 @053/1717z
17656-0 - Genslew for Proposal 10599 - Slot#12 @053/1718z
17658-0 - Genslew for Proposal 10599 - Slot#1 @053/1834z

COMPLETED OPS NOTES: (None)

SCHEDULED SUCCESSFUL
FGS GSacq 04 04
FGS REacq 09 09
OBAD with Maneuver 12 12

SIGNIFICANT EVENTS: (None)