Status Report

NASA Hubble Space Telescope Report #4432

By SpaceRef Editor
August 24, 2007
Filed under , ,
NASA Hubble Space Telescope 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 DAILY REPORT #4432

– 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)

SpaceRef staff editor.