Status Report

NASA Hubble Space Telescope Daily Report #4974

By SpaceRef Editor
November 21, 2009
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NASA Hubble Space Telescope Daily Report #4974


Continuing to Collect World Class Science

PERIOD COVERED: 5am November 17 – 5am November 18, 2009 (DOY 321/10:00z-322/10:00z)


ACS/WFC 11735

The LSD Project: Dynamics, Merging and Stellar Populations of a Sample of Well-studied LBGs at z~3

A large observational effort with the ground-based ESO/VLT telescopes allowed us to obtain deep, spatially-resolved, near-IR spectra of complete sample of 11 Lyman-Break Galaxies at z~3.1. These observations were used to obtain, for the first time, the metallicity and the dynamical properties of a sample of objects that, albeit small, is representative of the total population of the LBGs. We propose to use HST to obtain high-resolution optical and near-IR images of this sample of LBGs in order to study the broad-band morphology and the stellar light distribution of these galaxies. These images, exploiting the superior spatial resolution of HST images and the low-background : 1- will allow a precise measure of the dynamical mass from the velocity field derived with spectroscopy; 2- will permit a comparison of the distribution of star formation (from the line emission) with the underlying stellar population, and, 3- will be used to check if the complex velocity field and the multiple line-emitting regions detected in most targets can be ascribed to on-going mergers. This accurate study will shed light on a number of unsolved problems still affecting the knowledge of the LBGs.

COS/NUV 11900

NUV Internal/External Wavelength Scale Monitor

This program monitors the offsets between the wavelength scale set by the internal wavecal versus that defined by absorption lines in external targets. This is accomplished by observing two external radial velocity standard targets: HD187691 with G225M and G285M and HD6655 with G285M and G230L. The two standard targets have little flux in the wavelength range covered by G185M and so Feige 48 (sdO) is observed with this grating. Both Feige 48 and HD6655 are also observed in SMOV. The cenwaves observed in this program are a subset of the ones used during Cycle 17. Observing all cenwaves would require a considerably larger number of orbits. Constraints on scheduling of each target are placed so that each target is observed once every ~2-3 months. Observing the three targets every month would also require a considerably larger number of orbits.

FGS 11788

The Architecture of Exoplanetary Systems

Are all planetary systems coplanar? Concordance cosmogony makes that prediction. It is, however, a prediction of extrasolar planetary system architecture as yet untested by direct observation for main sequence stars other than the Sun. To provide such a test, we propose to carry out FGS astrometric studies on four stars hosting seven companions. Our understanding of the planet formation process will grow as we match not only system architecture, but formed planet mass and true distance from the primary with host star characteristics for a wide variety of host stars and exoplanet masses.

We propose that a series of FGS astrometric observations with demonstrated 1 millisecond of arc per-observation precision can establish the degree of coplanarity and component true masses for four extrasolar systems: HD 202206 (brown dwarf+planet); HD 128311 (planet+planet), HD 160691 = mu Arae (planet+planet), and HD 222404AB = gamma Cephei (planet+star). In each case the companion is identified as such by assuming that the minimum mass is the actual mass. For the last target, a known stellar binary system, the companion orbit is stable only if coplanar with the AB binary orbit.

STIS/CCD 11844

CCD Dark Monitor Part 1

The purpose of this proposal is to monitor the darks for the STIS CCD.

STIS/CCD 11846

CCD Bias Monitor-Part 1

The purpose of this proposal is to monitor the bias in the 1×1, 1×2, 2×1, and 2×2 bin settings at gain=1, and 1×1 at gain = 4, to build up high-S/N superbiases and track the evolution of hot columns.


Star Formation in Nearby Galaxies

Star formation is a fundamental astrophysical process; it controls phenomena ranging from the evolution of galaxies and nucleosynthesis to the origins of planetary systems and abodes for life. The WFC3, optimized at both UV and IR wavelengths and equipped with an extensive array of narrow-band filters, brings unique capabilities to this area of study. The WFC3 Scientific Oversight Committee (SOC) proposes an integrated program on star formation in the nearby universe which will fully exploit these new abilities. Our targets range from the well-resolved R136 in 30 Dor in the LMC (the nearest super star cluster) and M82 (the nearest starbursting galaxy) to about half a dozen other nearby galaxies that sample a wide range of star-formation rates and environments. Our program consists of broad band multiwavelength imaging over the entire range from the UV to the near-IR, aimed at studying the ages and metallicities of stellar populations, revealing young stars that are still hidden by dust at optical wavelengths, and showing the integrated properties of star clusters. Narrow-band imaging of the same environments will allow us to measure star-formation rates, gas pressure, chemical abundances, extinction, and shock morphologies. The primary scientific issues to be addressed are: (1) What triggers star formation? (2) How do the properties of star-forming regions vary among different types of galaxies and environments of different gas densities and compositions? (3) How do these different environments affect the history of star formation? (4) Is the stellar initial mass function universal or determined by local conditions?

WFC3/IR/S/C 11929

IR Dark Current Monitor

Analyses of ground test data showed that dark current signals are more reliably removed from science data using darks taken with the same exposure sequences as the science data, than with a single dark current image scaled by desired exposure time. Therefore, dark current images must be collected using all sample sequences that will be used in science observations. These observations will be used to monitor changes in the dark current of the WFC3-IR channel on a day-to-day basis, and to build calibration dark current ramps for each of the sample sequences to be used by GOs in Cycle 17. For each sample sequence/array size combination, a median ramp will be created and delivered to the calibration database system (CDBS).

WFC3/UV 11589

Hypervelocity Stars as Unique Probes of the Galactic Center and Outer Halo

We propose to obtain high-resolution images of 11 new hypervelocity stars in the Galactic halo in order to establish the first-epoch astrometric frame, as a part of a long-term program to measure precise proper motions in an absolute inertial frame. The origin of these recently discovered stars with extremely large positive radial velocities, in excess of the escape speed from the Galaxy, is consistent only with being ejected from the deep potential well of the massive black hole at the Galactic center. Reconstructing the full three-dimensional space motion of the hypervelocity stars, through astrometric proper motions, provides a unique opportunity to measure the shape and orientation of the triaxial dark matter halo. The hypervelocity stars allow determination of the Galactic potential out to 120 kpc, independently of and at larger distances than is afforded by tidal streams of satellite galaxies such as the Sagittarius dSph galaxy. Proper motions of the full set of hypervelocity stars will provide unique constraints on massive star formation in the environment of the Galactic center and on the history of stellar ejection by the supermassive black hole. We request one orbit with WFC3 for each of the 11 hypervelocity stars to establish their current positions relative to background galaxies. We request a repeated observation of these stars in Cycle 19, which will conclusively measure the astrometric proper motions.

WFC3/UVIS 11565

A Search for Astrometric Companions to Very Low-Mass, Population II Stars

We propose to carry out a Snapshot search for astrometric companions in a subsample of very low-mass, halo subdwarfs identified within 120 parsecs of the Sun. These ultra-cool M subdwarfs are local representatives of the lowest-mass H burning objects from the Galactic Population II. The expected 3-4 astrometric doubles that will be discovered will be invaluable in that they will be the first systems from which gravitational masses of metal-poor stars at the bottom of the main sequence can be directly measured.

WFC3/UVIS 11905

WFC3 UVIS CCD Daily Monitor

The behavior of the WFC3 UVIS CCD will be monitored daily with a set of full-frame, four-amp bias and dark frames. A smaller set of 2Kx4K subarray biases are acquired at less frequent intervals throughout the cycle to support subarray science observations. The internals from this proposal, along with those from the anneal procedure (Proposal 11909), will be used to generate the necessary superbias and superdark reference files for the calibration pipeline (CDBS).


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

HSTARS: (None)



FGS GSAcq 10 10
FGS REAcq 05 05
OBAD with Maneuver 10 10


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