NASA Hubble Space Telescope Daily Report #3951

HUBBLE SPACE TELESCOPE – Continuing to collect World Class Science

DAILY REPORT # 3951

PERIOD COVERED: UT September 22, 2005 (DOY 265)

OBSERVATIONS SCHEDULED

ACS/HRC 10556

Neutral Gas at Redshift z=0.5

Damped Lyman-alpha systems {DLAs} are used to track the bulk of the neutral hydrogen gas in the Universe. Prior to HST UV spectroscopy, they could only be studied from the ground at redshifts z>1.65. However, HST has now permitted us to discover 41 DLAs at z<1.65 in our previous surveys. Followup studies of these systems are providing a wealth of information about the evolution of the neutral gas phase component of the Universe. But one problem is that these 41 low-redshift systems are spread over a wide range of redshifts spanning nearly 70% of the age of the Universe. Consequently, past surveys for low-redshift DLAs have not been able to offer very good precision in any small redshift regime. Here we propose an ACS-HRC- PR200L spectroscopic survey in the redshift interval z=[0.37, 0.7] which we estimate will permit us to discover another 41 DLAs. This will not only allow us to double the number of low-redshift DLAs, but it will also provide a relatively high-precision regime in the low-redshift Universe that can be used to anchor evolutionary studies. Fortunately DLAs have high absorption equivalent width, so ACS-HRC-PR200L has high-enough resoultion to perform this proposed MgII-selected DLA survey.

ACS/HRC 10572

Resolving M32’s Main Sequence: A Critical Test for Stellar Population Studies

We propose to observe the M32 main-sequence turnoff {MSTO} with deep ACS/HRC B and V images. Only the superior resolution and blue sensitivity of ACS/HRC make this possible. M32 is the only elliptical galaxy close enough to allow direct observation of its MSTO – it is a vital laboratory for deciphering the stellar populations of all other elliptical galaxies, which can only be studied by the spectra of their integrated light, given their greater distances. Major questions about M32’s star formation history remain unanswered. Spectral studies suggest that M32 underwent a recent burst of star formation 3 to 8 billion years ago; observation of the M32 MSTO will confirm this directly. In the process, ACS will easily resolve more luminous components: hot blue stars, luminous, intermediate-age red clump and AGB stars, and any extended blue horizontal branch. These detailed CMDs will provide a direct comparison with population synthesis models for M32, providing a bridge to studies of the integrated light of more distant elliptical galaxies, a crucial ingredient for understanding their star formation histories. As M32 is projected against the edge of the M31 disk, an essential part of our proposal includes deep observation of an M31 disk field to allow the M32 photometry to be background corrected. These observations will reveal the star formation history of M31’s outer disk and are thus of interest in their own right.

ACS/WFC 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.

ACS/WFC 10581

Imaging a Proto-cluster at z=2.3: The Morphology-Density Relation at High Redshift

We propose deep ACS/WFC imaging in the HS1700+643 field, which contains a significant galaxy over-density at z=2.30+/-0.015. This structure is the largest and most robustly established cluster-sized over-density at z>1.5. We have spectroscopically confirmed 100 z~2 star-forming galaxies in this field and find significant differences in their stellar populations as a function of large-scale environment. Here we propose to measure the detailed morphological properties of this sample, to determine if the universal morphology-density relationship observed in the low-redshift universe is already in place in and around a forming proto-cluster region at high redshift. As well as providing a unique window into galaxy formation through studies of the z=2.3 proto-cluster, the HS1700+643 field has an extensive wealth of complementary data to recommend it. We will combine the new ACS observations with existing multi-wavelength imaging ranging from 0.3–8.0 microns, optical and near-IR spectroscopy, and narrow band imaging of z=2.3 H-alpha emitters, to understand the evolving properties of a complete and unbiased sample of high-redshift galaxies.

WFPC2 10356

WFPC2 Cycle 13 Decontaminations and Associated Observations

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

FLIGHT OPERATIONS SUMMARY:

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

HSTARS: (None)

COMPLETED OPS REQUEST:

17548-0 – Genslew for proposal 10487 – slot 8 @ 265/1527z

17549-0 – Genslew for proposal 10487 – slot 9 @ 265/1529z

COMPLETED OPS NOTES: (None)

                             SCHEDULED     SUCCESSFUL
FGS Gsacq                     5                      5
FGS Reacq                    10                    10
OBAD with Maneuver       24                    24

SIGNIFICANT EVENTS: (None)