Status Report

NASA Hubble Space Telescope Daily Report # 4617

By SpaceRef Editor
May 27, 2008
Filed under , ,
NASA Hubble Space Telescope Daily Report # 4617


Continuing to collect World Class Science

PERIOD COVERED: 5am May 22 – 5am May 23, 2008 (DOY 143/0900z-144/0900z)


FGS 11213

Distances to Eclipsing M Dwarf Binaries

We propose HST FGS observations to measure accurate distances of 5 nearby M dwarf eclipsing binary systems, from which model-independent luminosities can be calculated. These objects have either poor or no existing parallax measurements. FGS parallax determinations for these systems, with their existing dynamic masses determined to better than 0.5%, would serve as model-independent anchor points for the low-mass end of the mass-luminosity diagram.

NIC1/NIC2/NIC3 11330

NICMOS Cycle 16 Extended Dark

This takes a series of Darks in parallel to other instruments.

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 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.

NIC3 11334

NICMOS Cycle 16 Spectrophotometry

Observation of the three primary WD flux standards must be repeated to refine the NICMOS absolute calibration and monitor for sensitivity degradation. So far, NICMOS grism spectrophotometry is available for only ~16 stars with good STIS spectra at shorter wavelengths. There are more in the HST CALSPEC standard star data base with good STIS spectra that would also become precise IR standards with NICMOS absolute SED measurements. Monitoring the crucial three very red stars (M, L, T) for variability and better S/N in the IR. Apparent variability was discovered at shorter wavelengths during the ACS cross-calibration work that revealed a ~2% discrepancy of the cool star fluxes with respect to the hot primary WD standards. About a third of these stars are bright enough to do in one orbit, the rest require 2 orbits.

S/C 11320

NICMOS Focus Monitoring Cycle 16

This program is a version of the standard focus sweep used since cycle 7. It has been modified to go deeper and uses more narrow filters for improved focus determination. A new source was added in Cycle 14 in order to accommodate 2-gyro mode: the open cluster NGC1850. This source is part of the current proposal. The old target, the open cluster NGC3603, will be used whenever available and the new target used to fill the periods when NGC3603 is not visible. Steps: a) Use refined target field positions as determined from cycle 7 calibrations b) Use MULTIACCUM sequences of sufficient dynamic range to account for defocus c) Do a 17-point focus sweep, +/- 8mm about the PAM mechanical zeropoint for each cameras 1 and 2, in 1.0mm steps. For NIC3 we step from -0.5mm to -9.5mm relative to mechanical zero, in steps of 1.0mm. d) Use PAM X/Y tilt and OTA offset slew compensations refined from previous focus monitoring/optical alignment activities.

WFPC2 11196

An Ultraviolet Survey of Luminous Infrared Galaxies in the Local Universe

At luminosities above 10^11.4 L_sun, the space density of far-infrared selected galaxies exceeds that of optically selected galaxies. These Luminous Infrared Galaxies {LIRGs} are primarily interacting or merging disk galaxies undergoing starbursts and creating/fueling central AGN. We propose far {ACS/SBC/F140LP} and near {WFPC2/PC/F218W} UV imaging of a sample of 27 galaxies drawn from the complete IRAS Revised Bright Galaxy Sample {RBGS} LIRGs sample and known, from our Cycle 14 B and I-band ACS imaging observations, to have significant numbers of bright {23 < B < 21 mag} star clusters in the central 30 arcsec. The HST UV data will be combined with previously obtained HST, Spitzer, and GALEX images to {i} calculate the ages of the clusters as function of merger stage, {ii} measure the amount of UV light in massive star clusters relative to diffuse regions of star formation, {iii} assess the feasibility of using the UV slope to predict the far-IR luminosity {and thus the star formation rate} both among and within IR-luminous galaxies, and {iv} provide a much needed catalog of rest- frame UV morphologies for comparison with rest-frame UV images of high-z LIRGs and Lyman Break Galaxies. These observations will achieve the resolution required to perform both detailed photometry of compact structures and spatial correlations between UV and redder wavelengths for a physical interpretation our IRX-Beta results. The HST UV data, combined with the HST ACS, Spitzer, Chandra, and GALEX observations of this sample, will result in the most comprehensive study of luminous starburst galaxies to date.

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 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.

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!

WFPC2 11227

The orbital period for an ultraluminous X-ray source in NGC1313

The ultraluminous X-ray sources {ULXs} are extragalactic point sources with luminosities that exceed the Eddington luminosity for conventional stellar-mass black holes by factors of 10 – 100. It has been hotly debated whether the ULXs are just common stellar-mass black hole sources with beamed emission or whether they are sub-Eddington sources that are powered by the long-sought intermediate mass black holes {IMBH}. To firmly decide this question, one must obtain dynamical mass measurements through photometric and spectroscopic monitoring of the secondaries of these system. The crucial first step is to establish the orbital period of a ULX, and arguably the best way to achieve this goal is by monitoring its ellipsoidal light curve. The extreme ULX NGC1313 X-2 provides an outstanding target for an orbital period determination because its relatively bright optical counterpart {V = 23.5} showed a 15% variation between two HST observations separated by three months. This level of variability is consistent with that expected for a tidally distorted secondary star. Here we propose a set of 20 imaging observations with HST/WFPC2 to define the orbital period. This would be the first photometric measurement of the orbital period of a ULX binary. Subsequently, we will propose to obtain spectroscopic observations to obtain its radial velocity amplitude and thereby a dynamical estimate of its mass.


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

HSTARS: (None)



                         SCHEDULED      SUCCESSFUL

FGS GSacq                08                 08
FGS REacq                07                 07
OBAD with Maneuver       30                 30


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