Status Report

NASA Hubble Space Telescope Daily Report # 4615

By SpaceRef Editor
May 22, 2008
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NASA Hubble Space Telescope Daily Report # 4615


Continuing to collect World Class Science

PERIOD COVERED: 5am May 20 – 5am May 21, 2008 (DOY 141/0900z-142/0900z)


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

NIC3 11120

A Paschen-Alpha Study of Massive Stars and the ISM in the Galactic Center

The Galactic center (GC) is a unique site for a detailed study of a multitude of complex astrophysical phenomena, which may be common to nuclear regions of many galaxies. Observable at resolutions unapproachable in other galaxies, the GC provides an unparalleled opportunity to improve our understanding of the interrelationships of massive stars, young stellar clusters, warm and hot ionized gases, molecular clouds, large scale magnetic fields, and black holes. We propose the first large-scale hydrogen Paschen alpha line survey of the GC using NICMOS on the Hubble Space Telescope. This survey will lead to a high resolution and high sensitivity map of the Paschen alpha line emission in addition to a map of foreground extinction, made by comparing Paschen alpha to radio emission. This survey of the inner 75 pc of the Galaxy will provide an unprecedented and complete search for sites of massive star formation. In particular, we will be able to (1) uncover the distribution of young massive stars in this region, (2) locate the surfaces of adjacent molecular clouds, (3) determine important physical parameters of the ionized gas, (4) identify compact and ultra-compact HII regions throughout the GC. When combined with existing Chandra and Spitzer surveys as well as a wealth of other multi-wavelength observations, the results will allow us to address such questions as where and how massive stars form, how stellar clusters are disrupted, how massive stars shape and heat the surrounding medium, and how various phases of this medium are interspersed.

NIC3 11195

Morphologies of the Most Extreme High-Redshift Mid-IR-luminous Galaxies II: The `Bump’ Sources

The formative phase of some of the most massive galaxies may be extremely luminous, characterized by intense star- and AGN-formation. Till now, few such galaxies have been unambiguously identified at high redshift, and thus far we have been restricted to studying the low-redshift ultraluminous infrared galaxies as possible analogs. We have recently discovered a sample of objects which may indeed represent this early phase in galaxy formation, and are undertaking an extensive multiwavelength study of this population. These objects are optically extremely faint {R>26} but nevertheless bright at mid-infrared wavelengths {F[24um] > 0.5 mJy}. Mid-infrared spectroscopy with Spitzer/IRS reveals that they have redshifts z~2, implying luminosities ~1E13 Lsun. Their mid-IR SEDs fall into two broad, perhaps overlapping, categories. Sources with brighter F[24um] exhibit power-law SEDs and SiO absorption features in their mid-IR spectra characteristic of AGN, whereas those with fainter F[24um] show a “bump” characteristic of the redshifted 1.6um peak from a stellar population, and PAH emission characteristic of starformation. We have begun obtaining HST images of the brighter sources in Cycle 15 to obtain identifications and determine kpc-scale morphologies for these galaxies. Here, we aim to target the second class {the “bump” sources} with the goal of determining if these constitute morphologically different objects, or simply a “low-AGN” state of the brighter class. The proposed observations will help us determine whether these objects are merging systems, massive obscured starbursts {with obscuration on kpc scales!} or very reddened {locally obscured} AGN hosted by intrinsically low-luminosity galaxies.

WFPC2 11113

Binaries in the Kuiper Belt: Probes of Solar System Formation and Evolution

The discovery of binaries in the Kuiper Belt and related small body populations is powering a revolutionary step forward in the study of this remote region. Three quarters of the known binaries in the Kuiper Belt have been discovered with HST, most by our snapshot surveys. The statistics derived from this work are beginning to yield surprising and unexpected results. We have found a strong concentration of binaries among low-inclination Classicals, a possible size cutoff to binaries among the Centaurs, an apparent preference for nearly equal mass binaries, and a strong increase in the number of binaries at small separations. We propose to continue this successful program in Cycle 16; we expect to discover at least 13 new binary systems, targeted to subgroups where these discoveries can have the greatest impact.

WFPC2 11122

Expanding PNe: Distances and Hydro Models

We propose to obtain repeat narrowband images of a sample of eighteen planetary nebulae {PNe} which have HST/WFPC2 archival data spanning time baselines of a decade. All of these targets have previous high signal-to-noise WFPC2/PC observations and are sufficiently nearby to have readily detectable expansion signatures after a few years. Our main scientific objectives are {a} to determine precise distances to these PNe based on their angular expansions, {b} to test detailed and highly successful hydrodynamic models that predict nebular morphologies and expansions for subsamples of round/elliptical and axisymmetric PNe, and {c} to monitor the proper motions of nebular microstructures in an effort to learn more about their physical nature and formation mechanisms. The proposed observations will result in high-precision distances to a healthy subsample of PNe, and from this their expansion ages, luminosities, CSPN properties, and masses of their ionized cores. With good distances and our hydro models, we will be able to determine fundamental parameters {such as nebular and central star masses, luminosity, age}. The same images allow us to monitor the changing overall ionization state and to search for the surprisingly non-homologous growth patterns to bright elliptical PNe of the same sort seen by Balick & Hajian {2004} in NGC 6543. Non-uniform growth is a sure sign of active pressure imbalances within the nebula that require careful hydro models to understand.

WFPC2 11124

The Origin of QSO Absorption Lines from QSOs

We propose using WFPC2 to image the fields of 10 redshift z ~ 0.7 foreground {FG} QSOs which lie within ~29-151 kpc of the sightlines to high-z background {BG} QSOs. A surprisingly high fraction of the BG QSO spectra show strong MgII {2796,2803} absorption lines at precisely the same redshifts as the FG QSOs. The high resolution capabilities of WFPC2 are needed to understand the origin of these absorption systems, in two ways. First, we wish to explore the FG QSO environment as close as possible to the position of the BG QSO, to search for interloping group or cluster galaxies which might be responsible for the absorption, or irregularly shaped post-merger debris between the FG and BG QSO which may indicate the presence of large amount of disrupted gas along a sightline. Similarly, high resolution images are needed to search for signs of tidal interactions between any galaxies which might be found close to the FG QSO. Such features might provide evidence of young merging events causing the start of QSO duty cycles and producing outflows from the central AGN. Such winds may be responsible for the observed absorption lines. Second, we seek to measure the intrinsic parameters of the FG QSO host galaxy, such as luminosity and morphology, to correlate with the properties of the MgII absorption lines. We wish to observe each field through the F814W filter, close to the rest- frame B-band of the FG QSO. These blue data can reveal enhanced star formation regions close to the nucleus of the host galaxy, which may be indicative of galaxy mergers with the FG QSO host. The FG QSO environment offers quite a different set of phenomena which might be responsible for MgII absorption, providing an important comparison to studies of MgII absorption from regular field galaxies.

WFPC2 11202

The Structure of Early-type Galaxies: 0.1-100 Effective Radii

The structure, formation and evolution of early-type galaxies is still largely an open problem in cosmology: how does the Universe evolve from large linear scales dominated by dark matter to the highly non-linear scales of galaxies, where baryons and dark matter both play important, interacting, roles? To understand the complex physical processes involved in their formation scenario, and why they have the tight scaling relations that we observe today {e.g. the Fundamental Plane}, it is critically important not only to understand their stellar structure, but also their dark-matter distribution from the smallest to the largest scales. Over the last three years the SLACS collaboration has developed a toolbox to tackle these issues in a unique and encompassing way by combining new non-parametric strong lensing techniques, stellar dynamics, and most recently weak gravitational lensing, with high-quality Hubble Space Telescope imaging and VLT/Keck spectroscopic data of early-type lens systems. This allows us to break degeneracies that are inherent to each of these techniques separately and probe the mass structure of early-type galaxies from 0.1 to 100 effective radii. The large dynamic range to which lensing is sensitive allows us both to probe the clumpy substructure of these galaxies, as well as their low-density outer haloes. These methods have convincingly been demonstrated, by our team, using smaller pilot-samples of SLACS lens systems with HST data. In this proposal, we request observing time with WFPC2 and NICMOS to observe 53 strong lens systems from SLACS, to obtain complete multi-color imaging for each system. This would bring the total number of SLACS lens systems to 87 with completed HST imaging and effectively doubles the known number of galaxy-scale strong lenses. The deep HST images enable us to fully exploit our new techniques, beat down low-number statistics, and probe the structure and evolution of early-type galaxies, not only with a uniform data-set an order of magnitude larger than what is available now, but also with a fully coherent and self-consistent methodological approach!


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

HSTARS: (None)



                         SCHEDULED      SUCCESSFUL

FGS GSacq                06                  06
FGS REacq                07                  07
OBAD with Maneuver       26                  26


The motor current powering Gyro 6 increased from ~123 milli-ampere to ~185 milli-ampere around 141/20:46z. There was no impact to science operations.

SpaceRef staff editor.