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)