Status Report

NASA Hubble Space Telescope Daily Report #4257

By SpaceRef Editor
December 13, 2006
Filed under , ,
NASA Hubble Space Telescope Daily Report #4257


– Continuing to collect World Class Science

PERIOD COVERED: UT December 11, 2006 (DOY 345)


ACS/HRC 10878

An ACS Prism Snapshot Survey for z~2 Lyman Limit Systems

We propose to conduct a spectroscopic survey of Lyman limit absorbers at redshifts 1.7 < z < 2.2, using ACS/HRC and the PR200L prism. We have selected 100 quasars at 2.3 < z < 2.6 from the Sloan Digital Sky Survey Spectroscopic Quasar sample, for which no BAL signature is found at the QSO redshift and no strong metal absorption lines are present at z > 2.3 along the lines of sight. The survey has three main observational goals. First, we will determine the redshift frequency dN/dz of the LLS over the column density range 16.3

ACS/HRC 11041

ACS CCDs daily monitor

This program consists of a set of basic tests to monitor, the read noise, the development of hot pixels and test for any source of noise in ACS CCD detectors. The files, biases and dark will be used to create reference files for science calibration. This programme will be for the entire lifetime of ACS. For cycle 15 the program will cover 18 months 12.1.06->05.31.08 and it has been divied into three different proposal each covering six months. The three proposals are 11041-11042-11043.


A Cepheid Distance to the Coma Cluster

We propose to use the Advanced Camera for Surveys to search for Cepheid variables in two spiral galaxies in the core of the Coma cluster. A direct application of the canonical primary distance indicator at 100 Mpc will measure the far-field Hubble constant free of many of the systematic uncertainties which beset current determinations relying on secondary indicators. Establishing the far-field H_o with Cepheids will provide one of the strongest links in the extragalactic distance scale and will directly calibrate the fiducial fundamental plane of elliptical galaxies in Coma. With ACS/HRC, S/N=5 to 10 or better can be reached for Cepheids with periods of 40d to 70d at mean light in 5 orbits with the F606W filter if H_o=72 km/s/Mpc. Efficient detection and phasing can be done with twelve epochs optimally spaced for periods of 40-70d.

ACS/WFC 10633

GRB afterglows and host galaxies at very high redshifts

Cosmology is beginning to constrain the nature of the earliest stars and galaxies to form in the universe, but direct observation of galaxies at z>6 remains highly challenging due to their scarcity, intrinsically small size, and high luminosity distance. GRB afterglows, thanks to their extreme luminosities, offer the possibility of circumventing these normal constraints by providing redshifts and spectral information which couldn’t be obtained by direct observation of the hosts themselves. In addition, the association of GRBs with massive stars means that they are a tracer of star formation, and that their hosts are likely responsible for a large proportion of the ionizing radiation during that era. Our collaboration is mounting a campaign to rapidly identify and study candidate very high redshift bursts, bringing to bear a network of 2, 4 and 8m telescopes with nIR instrumentation. The capabilities of Swift to detect faint, distant GRBs, and to report accurate positions for many bursts in near real-time makes our program now feasible. HST is crucial to this endeavour, allowing us {a} to monitor the late time afterglows and hence compare them to lower-z bursts and test the use of GRBs as standard candles; and {b} characterise the basic properties, luminosities, and in some cases morphologies, of the hosts, which is essential to understanding these primordial galaxies and their relationship to other populations.

ACS/WFC 10880

The host galaxies of QSO2s: AGN feeding and evolution at high luminosities

Now that the presence of supermassive black holes in the nuclei of galaxies is a well established fact, other questions related to the AGN phenomena still have to be answered. Problems of particular interest are how the AGN gets fed, how the black hole evolves and how the evolution of the black hole is related to the evolution of the galaxy bulge. Here we propose to address some of these issues using ACS/WFC + F775W snapshot images of 73 QSO2s with redshifts in the range 0.3

ACS/WFC 10917

Afterglows and Environments of Short-Hard Gamma-Ray Bursts

Discovery of the first afterglows of short-hard bursts {SHBs} has led to a revolution in our understanding of these events, strongly suggesting that they originate in the mergers of compact-object binaries. Capitalizing on this progress, we propose to pursue the next generation of SHB observations with HST, tracking the decay of all accessible SHB afterglows to late times and pinpointing the location of several more within the context of their host galaxies. These observations will allow quantitative analysis of progenitor lifetimes and short burst environments, enable direct confrontation with population synthesis models, and provide updated event rate estimates for the LIGO and VIRGO gravitational-wave detectors that are now coming on-line.

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.

NIC2, ACS/WFC 10802

SHOES-Supernovae, HO, for the Equation of State of Dark energy

The present uncertainty in the value of the Hubble constant {resulting in an uncertainty in Omega_M} and the paucity of Type Ia supernovae at redshifts exceeding 1 are now the leading obstacles to determining the nature of dark energy. We propose a single, integrated set of observations for Cycle 15 that will provide a 40% improvement in constraints on dark energy. This program will observe known Cepheids in six reliable hosts of Type Ia supernovae with NICMOS, reducing the uncertainty in H_0 by a factor of two because of the smaller dispersion along the instability strip, the diminished extinction, and the weaker metallicity dependence in the infrared. In parallel with ACS, at the same time the NICMOS observations are underway, we will discover and follow a sample of Type Ia supernovae at z > 1. Together, these measurements, along with prior constraints from WMAP, will provide a great improvement in HST’s ability to distinguish between a static, cosmological constant and dynamical dark energy. The Hubble Space Telescope is the only instrument in the world that can make these IR measurements of Cepheids beyond the Local Group, and it is the only telescope in the world that can be used to find and follow supernovae at z > 1. Our program exploits both of these unique capabilities of HST to learn more about one of the greatest mysteries in science.

WFPC2 10744

WFPC2 Cycle 14 Decontaminations and Associated Observations

This proposal is for the WFPC2 decontamination. Also included are instrument monitors tied to decontamination: photometric stability check, focus monitor, pre- and post-decontamination internals {bias, intflats, kspots, & darks}, UV throughput check, VISFLAT sweep, and internal UV flat check.


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


10555 – GSAcq(2,1,1) failed to RGA Hold (Gyro Control) Upon acquisition of signal at 346/05:21:49, the GSAcq(2,1,1) scheduled at 346/05:03:05 – 04:11:10 was observed to have failed to RGA Hold due to search radius limit exceeded on FGS-1. One 486 ESB “a05” (FGS Coarse Track failed – Search Radius Limit Exceeded) was received. Pre-acquisition OBADs (RSS) attitude error corrections values not available pending future ETR Dump due to LOS.



                             SCHEDULED      SUCCESSFUL 
FGS GSacq                      05                      04 
FGS REacq                      10                      10 
OBAD with Maneuver  30                      30 

SpaceRef staff editor.