Status Report

NASA Hubble Space Telescope Daily Status Report #4683

By SpaceRef Editor
August 27, 2008
Filed under , ,


Continuing to collect World Class Science

PERIOD COVERED: 5am August 26 – 5am August 27, 2008 (DOY 239/0900z-240/0900z)


FGS 11211

An Astrometric Calibration of Population II Distance Indicators

In 2002 HST produced a highly precise parallax for RR Lyrae. That measurement resulted in an absolute magnitude, M{V}= 0.61+/-0.11, a useful result, judged by the over ten refereed citations each year since. It is, however, unsatisfactory to have the direct, parallax-based, distance scale of Population II variables based on a single star. We propose, therefore, to obtain the parallaxes of four additional RR Lyrae stars and two Population II Cepheids, or W Vir stars. The Population II Cepheids lie with the RR Lyrae stars on a common K-band Period-Luminosity relation. Using these parallaxes to inform that relationship, we anticipate a zero-point error of 0.04 magnitude. This result should greatly strengthen confidence in the Population II distance scale and increase our understanding of RR Lyrae star and Pop II Cepheid astrophysics.

NIC1 11205

The Effects of Multiplicity on the Evolution of Young Stellar Objects: A NICMOS Imaging Study

We propose to use NICMOS to investigate the multiplicity of young stellar objects (YSOs) in the Orion B molecular cloud. Previous observations with the Spitzer Space Telescope have revealed a remarkable star forming filament near the NGC 2068 reflection nebula. The population of YSOs associated with the filament exhibit a surprisingly wide range of circumstellar evolutionary states, from deeply embedded protostars to T Tauri accretion disks. Many of the circumstellar disks themselves show evidence for significant dust evolution, including grain growth and settling and cleared inner holes, apparently in spite of the very young age of these stars. We will estimate the binary fraction of a representative sample of objects in these various stages of evolution in order to test whether companions may play a significant role in that evolution.

NIC1/NIC2/NIC3 11820

NICMOS Post-SAA Calibration – CR Persistence Part 7

Internals for CR persistence

NIC2 11548

NICMOS Imaging of Protostars in the Orion A Cloud: The Role of Environment in Star Formation

We propose NICMOS observations of a sample of 252 protostars identified in the Orion A cloud with the Spitzer Space Telescope. These observations will image the scattered light escaping the protostellar envelopes, providing information on the shapes of outflow cavities, the inclinations of the protostars, and the overall morphologies of the envelopes. In addition, we ask for Spitzer time to obtain 55-95 micron spectra of 75 of the protostars. Combining these new data with existing 3.6 to 70 micron photometry and forthcoming 5-40 micron spectra measured with the Spitzer Space Telescope, we will determine the physical properties of the protostars such as envelope density, luminosity, infall rate, and outflow cavity opening angle. By examining how these properties vary with stellar density (i.e. clusters vs groups vs isolation) and the properties of the surrounding molecular cloud; we can directly measure how the surrounding environment influences protostellar evolution, and consequently, the formation of stars and planetary systems. Ultimately, this data will guide the development of a theory of protostellar evolution.

NIC2 11799

NICMOS Non-linearity Calibration for Faint Objects

NICMOS has played a key role in probing the deep near infrared regime for a decade. It has been the only instrument available to observe objects in the near infrared that are not visible from the ground. In particular, it has played a major role in the SN Ia observations at redshifts z>1. However, the calibration of NICMOS has turned out to be difficult due to the apparent non-linearity of the detectors. The NICMOS calibration team has described the non-linearity as a power law based on data in the range of ~50-5000 ADU/s. The correction relies on an extrapolation of two orders of magnitude in flux at count rates close to the sky level (0.1 ADU/s) where space observations are particularly prized – and where SN Ia observations are made. Precise measurements of faint objects require us to reduce the uncertainties from this extrapolation. Here we propose to derive the absolute calibration in the sky limited regime and to characterize the non-linearity over the entire dynamic range for the camera/filter combination: NIC2/F110W.

NIC3 11512

Molecules in Exoplanet Atmospheres

We propose to characterize the conditions, composition, and chemistry in two transiting exoplanet atmospheres using molecules as probes. This will be accomplished through high precision, near-IR spectroscopy during an interval that spans the primary and/or secondary eclipse events. We have selected the hot-Jovian HD 209458b and the warm-Neptune GJ 436b for spectroscopy from 1.4 to 2.5 microns and we expect to detect the molecules H2O, CH4, CO, CO2, and NH3. We will infer the atmospheric temperature-pressure profiles and determine the abundance of detected molecules; this will be done by comparing detailed radiative transfer models with emission and transmission spectra of the exoplanet atmospheres. Taken together with the existing observations of HD 189733b, the proposed measurements will probe the diversity of exoplanet atmospheres and the effects of radiation from the stellar primary.

WFPC2 11119

The Stellar Origins of Supernovae

Supernovae {SNe} have a profound effect on galaxies, and have been used recently as precise cosmological probes, resulting in the discovery of the accelerating Universe. They are clearly very important events deserving of intense study. Yet, even with nearly 4000 known SNe, we know relatively little about the stars which give rise to these powerful explosions. The main limitation has been the lack of spatial resolution in pre-SN imaging data. However, since 1999 our team has been at the vanguard of directly identifying SN progenitor stars in HST images. From this exciting new line of study, the emerging trend from 5 detections for Type II-Plateau SNe is that their progenitors appear to be relatively low mass {8 to 20 Msun} red supergiants, although more cases are needed. Nonetheless, the nature of the progenitors of Type Ib/c SNe, a subset of which are associated with the amazing gamma-ray bursts, remains ambiguous. Furthermore, we remain in the continually embarrassing situation that we still do not yet know which progenitor systems explode as Type Ia SNe, which are currently being used for precision cosmology. We propose to confirm the identities of the progenitors of 4 SNe within 17 Mpc, which we expect to occur during Cycle 16, through ToO observations using WFPC2/PC.

WFPC2 11130

AGNs with Intermediate-mass Black Holes: Testing the Black Hole-Bulge Paradigm, Part II

The recent progress in the study of central black holes in galactic nuclei has led to a general consensus that supermassive {10^6-10^9 solar mass} black holes are closely connected with the formation and evolutionary history of large galaxies, especially their bulge component. Two outstanding issues, however, remain unresolved. Can central black holes form in the absence of a bulge? And does the mass function of central black holes extend below 10^6 solar masses? Intermediate-mass black holes {<10^6 solar masses}, if they exist, may offer important clues to the nature of the seeds of supermassive black holes. Using the SDSS, our group has successfully uncovered a new population of AGNs with intermediate-mass black holes that reside in low-luminosity galaxies. However, very little is known about the detailed morphologies or structural parameters of the host galaxies themselves, including the crucial question of whether they have bulges or not. Surprisingly, the majority of the targets of our Cycle 14 pilot program have structural properties similar to dwarf elliptical galaxies. The statistics from this initial study, however, are really too sparse to reach definitive conclusions on this important new class of black holes. We wish to extend this study to a larger sample, by using the Snapshot mode to obtain WFPC2 F814W images from a parent sample of 175 AGNs with intermediate- mass black holes selected from our final SDSS search. We are particularly keen to determine whether the hosts contain bulges, and if so, how the fundamental plane properties of the host depend on the mass of their central black holes. We will also investigate the environment of this unique class of AGNs.

WFPC2 11218

Snapshot Survey for Planetary Nebulae in Globular Clusters of the Local Group

Planetary nebulae {PNe} in globular clusters {GCs} raise a number of interesting issues related to stellar and galactic evolution. The number of PNe known in Milky Way GCs, 4, is surprisingly low if one assumes that all stars pass through a PN stage. However, it is likely that the remnants of stars now evolving in Galactic GCs leave the AGB so slowly that any ejected nebula dissipates long before the star becomes hot enough to ionize it. Thus there should not be ANY PNe in Milky Way GCs–but there are four! It has been suggested that these PNe are the result of mergers of binary stars within GCs, i.e., that they are descendants of blue stragglers. The frequency of occurrence of PNe in external galaxies poses more questions, because it shows a range of almost an order of magnitude. I propose a Snapshot survey aimed at discovering PNe in the GC systems of Local Group galaxies more distant than the Magellanic Clouds. These clusters, some of which may be much younger than their counterparts in the Milky Way, might contain many more PNe than those of our own galaxy. I will use the standard technique of emission-line and continuum imaging, which easily discloses PNe.

WFPC2 11795

WFPC2 Cycle 16 UV Earth Flats

Monitor flat field stability. This proposal obtains sequences of earth streak flats to improve the quality of pipeline flat fields for the WFPC2 UV filter set. These Earth flats will complement the UV earth flat data obtained during cycles 8-15.


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


11455 GSAcq(2,1,1) failed, Scan Step Limit Exceeded on FGS 2 @ 239/2049z GSAcq(2,1,1) scheduled 239/20:45:44 – 20:53:49z failed to RGA Hold. Observations affected: WFPC #75-77 Proposal ID #11130.



                              SCHEDULED      SUCCESSFUL
FGS GSacq                       07              06
FGS REacq                       08              08
OBAD with Maneuver              30              30


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