Status Report

NASA Hubble Space Telescope Daily Report #4182

By SpaceRef Editor
August 22, 2006
Filed under , ,
NASA Hubble Space Telescope Daily Report #4182

HUBBLE SPACE TELESCOPE – Continuing to collect World Class Science


PERIOD COVERED: UT August 21, 2006 (DOY 233)



Lyman alpha morphology of local starburst galaxies

Our pilot imaging study of 6 local galaxies using ACS/SBC in the cosmologically important Lyman- alpha line has begun to reveal intriguing results. Here we propse ACS/HRC imaging of this sample, the approval of the which will allow for a significant increase in the impact of the original study and extend the limits of current understanding of Lyman-alpha escape. With this data we can accurately calibrate our Lyman-alpha line-only images and explore for the first time Lyman- alpha fluxes and equivalent widths in spatially resolved systems. These data would also allow us to test the current models of Lyman-alpha escape mechanisms and investigate possible correlations between Lyman-alpha emission and other local parameters such as age and internal reddening. The addition of high-resolution H-alpha data allows us to quantitatively study the decoupling of Lyman-alpha from non-resonant radiation and spatially explore the destruction and attenuation of Lyman-alpha. The study will go a long way towards resolving the outstanding issues complicating the interpretation of high redshift studies and the use of Lyman-alpha to quantitatively study the distant universe.


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. Changes from cycle 13:- The default gain for WFC is 2 e-/DN. As before bias frames will be collected for both gain 1 and gain 2. Dark frames are acquired using the default gain {2}. This program cover the period May, 31 2006- Oct, 1-2006. The first half of the program has a different proposal number: 10729.

ACS/SBC 10554

Globular Cluster Systems of Elliptical Galaxies in Low Density Environments

We propose to use the ACS/WFC to determine colour {metallicity} distributions and luminosity functions for the globular cluster populations in a well-defined sample of elliptical galaxies in low- density environments, and to compare the results with similar samples taken from a rich cluster environment. Low-luminosity ellipticals are now recognized to play a pivotal role in testing hierarchical models of galaxy formation, and their globular cluster populations provide a unique probe of their star formation and metal enrichment history. The data will be used to {i} determine whether the bimodal colour distributions indicative of multiple formation epochs in luminous ellipticals are also prevalent in low-luminosity field ellipticals; {ii} place joint constraints on age and metallicity in systems with more than one population and determine the spread of ages in any one system; {iii} test whether cluster destruction processes {e.g. tidal shocking} are more effective in low-luminosity ellipticals, as predicted from their higher mass densities. ACS observations are essential to eliminate foreground/background contamination and to probe deep into the luminosity function to obtain a good statistical sample of clusters. The TAC has previously awarded HST time to two large surveys of globular cluster systems in rich cluster environments, but there is currently no comparable survey in low-density environments with which to compare these results.

ACS/SBC 10739

Internal Flat Field Stability

The stability of the CCD flat fields will be monitored using the calibration lamps and a sub-sample of the filter set. For the SBC imaging filters, differences in the low-frequency flat field structure with wavelength will be assessed. New high signal P-flats will be obtained for the SBC prisms.

ACS/WFC 10258

Tracing the Emergence of the Hubble Sequence Among the Most Luminous and Massive Galaxies

There is mounting evidence that the redshift range 1 < z < 2 was an important era when massive galaxies assembled their stellar content and assumed their present--day morphologies. Despite extensive HST imaging surveys, however, there is very little data in the optical rest frame {i.e., observed near--infrared} on the morphologies of the most luminous galaxies at these redshifts. We propose to image a carefully selected set of 20 of the most luminous, K--band selected GOODS galaxies at 1.3 < z < 2, using NICMOS camera 2. This offers diffraction--limited, critically sampled imaging at 1.6 microns to ensure the best angular resolution for comparison to ACS. The galaxies are chosen to span a simple 4--fold parameter space of morphological and spectral type, in order to provide the most information about the variety of massive galaxy properties in this redshift range. We will investigate the emergence of large scale--length disks, stable spiral structure, mature bulges with red stellar populations, central bar structures, the incidence of disturbed morphology, the existence {or lack thereof} of blue ellipticals, and other questions that concern the evolution and maturation of the brightest, largest, and most massive ordinary galaxies in this critical redshift range.

ACS/WFC/NIC2 10496

Decelerating and Dustfree: Efficient Dark Energy Studies with Supernovae and Clusters

We propose a novel HST approach to obtain a dramatically more useful “dust free” Type Ia supernovae {SNe Ia} dataset than available with the previous GOODS searches. Moreover, this approach provides a strikingly more efficient search-and-follow-up that is primarily pre- scheduled. The resulting dark energy measurements do not share the major systematic uncertainty at these redshifts, that of the extinction correction with a prior. By targeting massive galaxy clusters at z > 1 we obtain a five-times higher efficiency in detection of Type Ia supernovae in ellipticals, providing a well-understood host galaxy environment. These same deep cluster images then also yield fundamental calibrations required for future weak lensing and Sunyaev-Zel’dovich measurements of dark energy, as well as an entire program of cluster studies. The data will make possible a factor of two improvement on supernova constraints on dark energy time variation, and much larger improvement in systematic uncertainty. They will provide both a cluster dataset and a SN Ia dataset that will be a longstanding scientific resource.

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.

NIC3/ACS/WFC 10504

Characterizing the Sources Responsible for Cosmic Reionization

Our group has demonstrated the role that massive clusters, acting as powerful cosmic lenses, can play in constraining the abundance and properties of low-luminosity star-forming sources beyond z~6; such sources are thought to be responsible for ending cosmic reionization. The large magnification possible in the critical regions of well-constrained clusters brings sources into view that lie at or beyond the limits of conventional exposures such as the UDF, as well as those in imaging surveys being undertaken with IRAC onboard Spitzer. We have shown that the combination of HST and Spitzer is particularly effective in delivering the physical properties of these distant sources, constraining their mass, age and past star formation history. Indirectly, we therefore gain a valuable glimpse to yet earlier epochs. Recognizing the result {and limitations} of the UDF exposure, we propose a systematic search through 6 lensing clusters with ACS and NICMOS for further z~6-7 sources in conjunction with existing deep IRAC data. Our survey will mitigate cosmic variance and extend the search both to lower luminosities and, by virtue of the NICMOS/IRAC combination, to higher redshift. The goal is to count and characterize representative sources at z~6-10 and to delineate the redshift range of activity for the planning of future observations.


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

HSTARS: (None)



                          SCHEDULED      SUCCESSFUL 
FGS GSacq                07                     07 
FGS REacq                08                     08 
OBAD with Maneuver   28                     28 


SpaceRef staff editor.