NASA Hubble Space Telescope Daily Status Report #4352

Notice: For the foreseeable future, the daily reports may contain apparent discrepancies between some proposal descriptions and the listed instrument usage. This is due to the conversion of previously approved ACS WFC or HRC observations into WFPC2, or NICMOS observations subsequent to the loss of ACS CCD science capability in late January.

HUBBLE SPACE TELESCOPE DAILY REPORT # 4352

– Continuing to collect World Class Science

PERIOD COVERED: UT April 30, 2007 (DOY 120)

OBSERVATIONS SCHEDULED

ACS/SBC 10864

Mapping the Gaseous Content of Protoplanetary and Young Planetary Systems with ACS

One of the key problems in planetary system formation is understanding how rapidly, and over what time interval Jovian planets can form. Dust in the protoplanetary disk is critical in planetesimal formation, but it is the gas which produces giant planets, and which is essential for their migration. However, compared to data on the circumstellar dust, information on the gas component is sparse, especially in the planet-formation zone. This severely limits our ability to put observational constraints on giant planet formation, except to note that the process must be largely complete by 12 Myr, given the paucity of Herbig Ae or classical T Tauri stars older than 10-12 Myr. In the FUV, photo-excited molecular hydrogen transitions have the requisite contrast to the stellar photosphere, accretion shock, and reflection nebulosity, and can be traced 50-100 AU from the exciting stars in both envelopes and outflow cavities and protoplanetary disks. Central disk cavities, an expected consequence of planet formation, larger than 0.1″ are directly detectable in HST FUV spectra, while smaller cavities may be detected by comparison with protoplanetary disks which are still accreting onto their stars. We propose augmenting existing HST coronagraphic imagery of 6 Herbig Fe and T Tauri disks with ACS Solar-Blind Channel Lyman alpha imagery and slitless spectroscopy simultaneously sampling the disk in molecular hydrogen and small-grain reflection nebulosity. These data will be used to quantify the amount of vertical stratification in these disks, to map the mass-loss geometry from the star, and to determine whether removal of molecular material preceeds, lags, or is contemporary with clearing of the dust.

WFPC2 11024

WFPC2 CYCLE 15 INTERNAL MONITOR

This calibration proposal is the Cycle 15 routine internal monitor for WFPC2, to be run weekly to monitor the health of the cameras. A variety of internal exposures are obtained in order to provide a monitor of the integrity of the CCD camera electronics in both bays {both gain 7 and gain 15 — to test stability of gains and bias levels}, a test for quantum efficiency in the CCDs, and a monitor for possible buildup of contaminants on the CCD windows. These also provide raw data for generating annual super-bias reference files for the calibration pipeline.

NIC1 10889

The Nature of the Halos and Thick Disks of Spiral Galaxies

We propose to resolve the extra-planar stellar populations of the thick disks and halos of seven nearby, massive, edge-on galaxies using ACS, NICMOS, and WFPC2 in parallel. These observations will provide accurate star counts and color-magnitude diagrams 1.5 magnitudes below the tip of the Red Giant Branch sampled along the two principal axes and one intermediate axis of each galaxy. We will measure the metallicity distribution functions and stellar density profiles from star counts down to very low average surface brightnesses, equivalent to ~32 V-mag per square arcsec. These observations will provide the definitive HST study of extra-planar stellar populations of spiral galaxies. Our targets cover a range in galaxy mass, luminosity, and morphology and as function of these galaxy properties we will provide: – The first systematic study of the radial and isophotal shapes of the diffuse stellar halos of spiral galaxies – The most detailed comparative study to date of thick disk morphologies and stellar populations – A comprehensive analysis of halo and thick disk metallicity distributions as a function of galaxy type and position within the galaxy. – A sensitive search for tidal streams – The first opportunity to directly relate globular cluster systems to their field stellar population We will use these fossil records of the galaxy assembly process preserved in the old stellar populations to test halo and thick disk formation models within the hierarchical galaxy formation scheme. We will test LambdaCDM predictions on sub-galactic scales, where it is difficult to test using CMB and galaxy redshift surveys, and where it faces its most serious difficulties.

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

NIC3 11080

Exploring the Scaling Laws of Star Formation

As a variety of surveys of the local and distant Universe are approaching a full census of galaxy populations, our attention needs to turn towards understanding and quantifying the physical mechanisms that trigger and regulate the large-scale star formation rates {SFRs} in galaxies.

WFPC2 11023

WFPC2 CYCLE 15 Standard Darks – part 1

This dark calibration program obtains dark frames every week in order to provide data for the ongoing calibration of the CCD dark current rate, and to monitor and characterize the evolution of hot pixels. Over an extended period these data will also provide a monitor of radiation damage to the CCDs.

WFPC2 11083

The Structure, Formation and Evolution of Galactic Cores and Nuclei

A surprising result has emerged from the ACS Virgo Cluster Survey {ACSVCS}, a program to obtain ACS/WFC gz imaging for a large, unbiased sample of 100 early-type galaxies in the Virgo Cluster. On subarcsecond scales {i.e., <0.1"-1"}, the HST brightness profiles vary systematically from the brightest giants {which have nearly constant surface brightness cores} to the faintest dwarfs {which have compact stellar nuclei}. Remarkably, the fraction of galaxy mass contributed by the nuclei in the faint galaxies is identical to that contributed by supermassive black holes in the bright galaxies {0.2%}. These findings strongly suggest that a single mechanism is responsible for both types of Central Massive Object: most likely internally or externally modulated gas inflows that feed central black holes or lead to the formation of "nuclear star clusters". Understanding the history of gas accretion, star formation and chemical enrichment on subarcsecond scales has thus emerged as the single most pressing question in the study of nearby galactic nuclei, either active or quiescent. We propose an ambitious HST program {199 orbits} that constitutes the next, obvious step forward: high-resolution, ultraviolet {WFPC2/F255W} and infrared {NIC1/F160W} imaging for the complete ACSVCS sample. By capitalizing on HST's unique ability to provide high-resolution images with a sharp and stable PSF at UV and IR wavelengths, we will leverage the existing optical HST data to obtain the most complete picture currently possible for the history of star formation and chemical enrichment on these small scales. Equally important, this program will lead to a significant improvement in the measured structural parameters and density distributions for the stellar nuclei and the underlying galaxies, and provide a sensitive measure of "frosting" by young stars in the galaxy cores. By virtue of its superb image quality and stable PSF, NICMOS is the sole instrument capable of the IR observations proposed here. In the case of the WFPC2 observations, high-resolution UV imaging {< 0.1"} is a capability unique to HST, yet one that could be lost at any any time.

FLIGHT OPERATIONS SUMMARY:

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

HSTARS: (None)

COMPLETED OPS REQUEST:

18055-0 – Halt and Restart of the KF for Clock Rollover

18054-0 – Preview KF Sun Vector Data via Telemetry Diags

COMPLETED OPS NOTES: (None)

                       SCHEDULED      SUCCESSFUL 

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

SIGNIFICANT EVENTS: (None)