Status Report

NASA Hubble Space Telescope Daily Status Report #4659

By SpaceRef Editor
July 25, 2008
Filed under , ,


Continuing to collect World Class Science

PERIOD COVERED: 5am July 23 – 5am July 24, 2008 (DOY 205/0900z-206/0900z)


FGS 11212

Filling the Period Gap for Massive Binaries

The current census of binaries among the massive O-type stars is seriously incomplete for systems in the period range from years to millennia because the radial velocity variations are too small and the angular separations too close for easy detection. Here we propose to discover binaries in this observational gap through a Faint Guidance Sensor SNAP survey of relatively bright targets listed in the Galactic O Star Catalog. Our primary goal is to determine the binary frequency among those in the cluster/association, field, and runaway groups. The results will help us assess the role of binaries in massive star formation and in the processes that lead to the ejection of massive stars from their natal clusters. The program will also lead to the identification of new, close binaries that will be targets of long term spectroscopic and high angular resolution observations to determine their masses and distances. The results will also be important for the interpretation of the spectra of suspected and newly identified binary and multiple systems.

NIC1/NIC2/NIC3 11321

NICMOS Cycle 16 Flats Stability

This calibration proposal is the Cycle 16 NICMOS flat field monitor program. A series of camera 1, 2, & 3 flat fields will be obtained to monitor the health of the cameras.

NIC1/NIC2/NIC3 8795

NICMOS Post-SAA Calibration – CR Persistence Part 6

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 i mages. Each observation will need its own CRMAP, as different SAA passages leave different imprints on the NICMOS detectors.

NIC2 11157

NICMOS Imaging Survey of Dusty Debris Around Nearby Stars Across the Stellar Mass Spectrum

Association of planetary systems with dusty debris disks is now quite secure, and advances in our understanding of planet formation and evolution can be achieved by the identification and characterization of an ensemble of debris disks orbiting a range of central stars with different masses and ages. Imaging debris disks in starlight scattered by dust grains remains technically challenging so that only about a dozen systems have thus far been imaged. A further advance in this field needs an increased number of imaged debris disks. However, the technical challenge of such observations, even with the superb combination of HST and NICMOS, requires the best targets. Recent HST imaging investigations of debris disks were sample-limited not limited by the technology used. We performed a search for debris disks from a IRAS/Hipparcos cross correlation which involved an exhaustive background contamination check to weed out false excess stars. Out of ~140 identified debris disks, we selected 22 best targets in terms of dust optical depth and disk angular size. Our target sample represents the best currently available target set in terms of both disk brightness and resolvability. For example, our targets have higher dust optical depth, in general, than newly identified Spitzer disks. Also, our targets cover a wider range of central star ages and masses than previous debris disk surveys. This will help us to investigate planetary system formation and evolution across the stellar mass spectrum. The technical feasibility of this program in two-gyro mode guiding has been proven with on-orbit calibration and science observations during HST cycles 13, 14, and 15.

NIC3 11107

Imaging of Local Lyman Break Galaxy Analogs: New Clues to Galaxy Formation in the Early Universe

We have used the ultraviolet all-sky imaging survey currently being conducted by the Galaxy Evolution Explorer {GALEX} to identify for the first time a rare population of low-redshift starbursts with properties remarkably similar to high-redshift Lyman Break Galaxies {LBGs}. These “compact UV luminous galaxies” {UVLGs} resemble LBGs in terms of size, SFR, surface brightness, mass, metallicity, kinematics, dust, and color. The UVLG sample offers the unique opportunity of investigating some very important properties of LBGs that have remained virtually inaccessible at high redshift: their morphology and the mechanism that drives their star formation. Therefore, in Cycle 15 we have imaged 7 UVLGs using ACS in order to 1} characterize their morphology and look for signs of interactions and mergers, and 2} probe their star formation histories over a variety of timescales. The images show a striking trend of small- scale mergers turning large amounts of gas into vigorous starbursts {a process referred to as dissipational or “wet” merging}. Here, we propose to complete our sample of 31 LBG analogs using the ACS/SBC F150LP {FUV} and WFPC2 F606W {R} filters in order to create a statistical sample to study the mechanism that triggers star formation in UVLGs and its implications for the nature of LBGs. Specifically, we will 1} study the trend between galaxy merging and SFR in UVLGs, 2} artificially redshift the FUV images to z=1-4 and compare morphologies with those in similarly sized samples of LBGs at the same rest-frame wavelengths in e.g. GOODS, UDF, and COSMOS, 3} determine the presence and morphology of significant stellar mass in “pre-burst” stars, and 4} study their immediate environment. Together with our Spitzer {IRAC+MIPS}, GALEX, SDSS and radio data, the HST observations will form a unique union of data that may for the first time shed light on how the earliest major episodes of star formation in high redshift galaxies came about. This proposal was adapted from an ACS HRC+WFC proposal to meet the new Cycle 16 observing constraints, and can be carried out using the ACS/SBC and WFPC2 without compromising our original science goals.

WFPC2 11156

Monitoring Active Atmospheres on Uranus and Neptune

We propose Snapshot observations of Uranus and Neptune to monitor changes in their atmospheres on time scales of weeks and months. Uranus equinox is only months away, in December 2007. Hubble Space Telescope observations during the past several years {Hammel et al. 2005, Icarus 175, 284 and references therein} have revealed strongly wavelength- dependent latitudinal structure, the presence of numerous visible-wavelength cloud features in the northern hemisphere, at least one very long-lived discrete cloud in the southern hemisphere, and in 2006 the first dark spot ever seen on Uranus. Long-term ground-based observations {Lockwood and Jerzekiewicz, 2006, Icarus 180, 442; Hammel and Lockwood 2007, Icarus 186, 291} reveal seasonal brightness changes whose origins are not well understood. Recent near- IR images of Neptune obtained using adaptive optics on the Keck Telescope, together with HST observations {Sromovsky et al. 2003, Icarus 163, 256 and references therein} which include previous Snapshot programs {GO 8634, 10170, 10534} show a general increase in activity at south temperate latitudes until 2004, when Neptune returned to a rather Voyager-like appearance. Further Snapshot observations of these two dynamic planets will elucidate the nature of long-term changes in their zonal atmospheric bands and clarify the processes of formation, evolution, and dissipation of discrete albedo features.

WFPC2 11544

The Dynamical Legacy of Star Formation

We propose to use WFPC2 to conduct a wide-field imaging survey of the young cluster IC348. This program, in combination with archival HST observations, will allow us to measure precise proper motions for individual cluster members, characterizing the intra-cluster velocity dispersion and directly studying the dynamical signatures of star formation and early cluster evolution. Our projected astrometric precision (~1 mas in each epoch) will allow us to calculate individual stellar velocities to unprecedented precision (<0.5 mas/yr; <1 km/s) and directly relate these velocities to observed spatial substructure within the cluster. This survey will also allow us to probe small-scale star formation physics by searching for high-velocity stars ejected from decaying multiple systems, expanding our knowledge of multiplicity in dense environments, and identifying new substellar and planetary-mass cluster members based on kinematic membership tests.

WFPC2/NIC2 11173

Completing an Accurate Map of M31 Microlensing

The halo microlensing masses detected in the MACHO survey (claimed to compose about 20% of the Galaxy’s mass) represent a major enigma in astrophysics, one that must be effectively cross-examined by an independent test. We have completed a large, densely-sampled survey of M31 that can reveal in another galaxy such a halo microlensing signal if it exists. In a previous HST/ACS+WFPC2 program (GO 10273, Cycle 13, 16 orbits) we were able to learn considerably more about a subsample of these M31 microlensing events. We were pleased to find that in most cases we could isolate the source star for each event, find its baseline flux and colors (essential for ruling out classes of confusing variable stars), test for misidentification of background supernovae, and measure the Einstein parameters, which constrain the range of most likely lens mass. (These Cycle 13 results are published in The Astrophysical Journal Letters.) We propose to finish the job, taking a similar series of exposures to more than double the sample of well-constrained microlensing events, which together with the larger ground-based sample for which we are completing our analyses will provide 20-30 M31 bona fide microlensing events observed by HST. This will be done via a series of targeted PC exposures, meant to maximize the number of candidates studied, one (or two) at a time. A sample of this size and quality should be sufficient to settle the issue of a significant contribution to the halos of galaxies by stellar-mass lenses. Furthermore, if there is a surplus of such microlensing events above what might be expected from stars alone, the higher quality of information will allow us to more accurately describe the spatial distribution of these lenses. We will also complete several unique studies of M31 stellar populations, both in support of the microlensing measurement and in their own right.


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


#11406 GSACQ(2,3,2) fine lock backup on FGS2 during LOS @205/11:59:26z

QF3STOPF and QSTOP flags were set on FGS 3. Post acquisition Observations affected: ACS #3, Proposal #11107; and NICMOS #47, Proposal #08795.

#11408 GSAcq(2,3,2) failed to RGA Hold (Gyro Control) @205/18:53:30z due to a Search Radius Limit Exceeded Error on FGS-2.

Also received “T2G OPEN LOOP TIMEOUT” and “TxG FHST SANITY CHECK FAILED” ESB errors. Observations affected: WFPC #91-94, Proposal ID#11173.



                              SCHEDULED    SUCCESSFUL
FGS GSacq                       14             13
FGS REacq                        0             0
OBAD with Maneuver              28             26


SpaceRef staff editor.