Daily Report # 4432

Notice: Due to the conversion of some ACS WFC or HRC observations into
WFPC2, or NICMOS observations after the loss of ACS CCD science
capability in January, there may be an occasional discrepancy between
a proposal's listed (and correct) instrument usage and the abstract
that follows it.


HUBBLE SPACE TELESCOPE - Continuing to collect World Class Science

DAILY REPORT***** # 4432

PERIOD COVERED: UT August 22, 2007 (DOY 234)

OBSERVATIONS SCHEDULED

WFPC2 10787

Modes of Star Formation and Nuclear Activity in an Early Universe
Laboratory

Nearby compact galaxy groups are uniquely suited to exploring the
mechanisms of star formation amid repeated and ongoing gravitational
encounters, conditions similar to those of the high redshift universe.
These dense groups host a variety of modes of star formation, and they
enable fresh insights into the role of gas in galaxy evolution. With
Spitzer mid-IR observations in hand, we have begun to obtain high
quality, multi-wavelength data for a well- defined sample of 12 nearby
{4500km/s} compact groups covering the full range of evolutionary
stages. Here we propose to obtain sensitive BVI images with the
ACS/WFC, deep enough to reach the turnover of the globular cluster
luminosity function, and WFPC2 U-band and ACS H-alpha images of
Spitzer-identified regions hosting the most recent star formation. In
total, we expect to detect over 1000 young star clusters forming
inside and outside galaxies, more than 4000 old globular clusters in
40 giant galaxies {including 16 early-type galaxies}, over 20 tidal
features, approximately 15 AGNs, and intragroup gas in most of the 12
groups. Combining the proposed ACS images with Chandra observations,
UV GALEX observations, ground-based H-alpha imaging, and HI data, we
will conduct a detailed study of stellar nurseries, dust, gas
kinematics, and AGN.

NIC1 11304

The L/T Transition in the Photospheres of Young Sub-Stellar
Companions

We propose 3.6-8.0 micron IRAC photometry and 5.5?22 micron
low-resolution IRS spectroscopy and imaging of the sub-stellar
companions to the ~0.3 Gyr old stars HN Peg and HD 203030. The
spectral types of the two secondaries span the critical transition
between L and T dwarfs, which is characterized by a rapid
sedimentation of dust and appearance of methane in sub-stellar
photospheres. HN Peg B {T2.5} and HD 203030 B {L7.5} are the youngest
known brown dwarfs at this transition, and present a unique
opportunity to examine the role of surface gravity in the process.
Both objects stand out from 1-10 Gyr L/T transition dwarfs in the
field because they are underluminous in the near- IR compared to the
expected luminosities for their ages. Probable reasons include: {1} a
decrease in the effective temperature at the onset of methane
formation at lower surface gravities in sub-stellar photospheres, or
{2} a shift in the emitted flux from the near-IR to the mid-IR region
of the SED of young brown dwarfs. The mid-IR is key for distinguishing
between these two hypotheses because it contains several fundamental
molecular transitions that create deep absorption bands in the SEDs of
L and T dwarfs, and that are inaccessible for study from the ground.
Our existing IRAC photometry of HN Peg B does reveal a 0.3-0.5 mag
excess in its 3.6-8.0 micron SED. However, this excess is insufficient
to account for the lower luminosity of HN Peg B, and indicates that
both of the above hypotheses may hold true to certain degrees. With
the present proposal we aim to independently confirm the
gravity-dependent behavior of L/T transition photospheres in the
mid-IR through IRAC photometry of HD 203030 B. We will also seek the
culprit for the mid- IR excess of HN Peg B through low resolution
spectroscopy and peak-up imaging with IRS. To check for possible
duplicity of HN Peg B as the reason for its excess, we request high
angular resolution imaging with HST to complement our lower resolution
Spitzer imaging.

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 DARKs. 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.

WFPC2 11031

CTE Background Dependence Closeout

Measuring the charge transfer efficiency {CTE} of an astronomical CCD
camera is crucial to determining the CCD's photometric fidelity across
the field of view. WFPC2's CTE has degraded steadily over the last 13
years because of continuous exposure to trapped particles in HST's
radiation environment. The fraction of photometric signal lost from
WFPC2's CTI {charge transfer inefficiency} is a function of WFPC2's
time in orbit, the integrated signal in the image, the location of the
image on the CCD, and the background signal. Routine monitoring of
WFPC2's CTE over the last 13 years permits an assessment of all but
the last condition. The dependence of CTE on background signal must be
characterized, however, because a large fraction of WFPC2 images have
been obtained under conditions of significant sky background. This
program aims to assess the end-of-life CTE of WFPC2's CCDs separately
as a function of background signal. Traditional images of an
off-center field in NGC 5139 {Omega Cen} are recorded after
preflashing {or before postflashing} the CCDs with internal lamps to
provide average background signals of 0-160 e-, which span the range
of sky backgrounds observed in ~99% of long-exposure narrow- and
broad-band WFPC2 images.

WFPC2 11176

Location and the Origin of Short Gamma-Ray Bursts

During the past decade extraordinary progress has been made in
determining the origin of long-duration gamma-ray bursts. It has been
conclusively shown that these objects derive from the deaths of
massive stars. Nonetheless, the origin of their observational cousins,
short-duration gamma-ray bursts {SGRBs} remains a mystery. While SGRBs
are widely thought to result from the inspiral of compact binaries,
this is a conjecture. A number of hosts of SGRBs have been identified,
and have been used by some to argue that SGRBs derive primarily from
an ancient population {~ 5 Gyr}; however, it is not known whether this
conclusion more accurately reflects selection biases or astrophysics.
Here we propose to employ a variant of a technique that we pioneered
and used to great effect in elucidating the origins of long-duration
bursts. We will examine the degree to which SGRB locations trace the
red or blue light of their hosts, and thus old or young stellar
populations. This approach will allow us to study the demographics of
the SGRB population in a manner largely free of the distance dependent
selection effects which have so far bedeviled this field, and should
give direct insight into the age of the SGRB progenitor population.

FLIGHT OPERATIONS SUMMARY:

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

HSTARS:

10953 - GSAcq (1,2,1) failed to RGA Hold

GSAcq (1,2,1) scheduled from 235/07:46:05-07:53:32 failed to RGA Hold
due to QSTOP flag on FGS 1.

OBAD #1: V1 69.79, V2 -1843.49, V3 63.91, RSS 1845.92
OBAD #2: V1 -8.78, V2 4.49, V3 6.40, RSS 11.76

At AOS 235/08:55:19 OBAD MAP: V1 -51.55, V2 -823.28, V3 -35.36, RSS
825.65

COMPLETED OPS REQUEST: (None)

COMPLETED OPS NOTES: (None)

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

FGS GSacq************** 06**************** 05
FGS REacq************** 08**************** 08
OBAD with Maneuver **** 28**************** 28

SIGNIFICANT EVENTS: (None)