HUBBLE SPACE TELESCOPE - Continuing to collect World Class Science

DAILY REPORT       # 4507

PERIOD COVERED: UT December 13, 2007 (DOY 347)

OBSERVATIONS SCHEDULED

ACS/SBC 11215

New Sightlines for the Study of Intergalactic Helium: Dozens of

High-Confidence, UV- Bright Quasars from SDSS/GALEX

The reionization of IGM helium is thought to have occurred at redshifts

of z=3 to 4. Detailed study of HeII Lyman-alpha absorption toward a

handful of QSOs at 2.7<z<3.3 demonstrated the high potential of such IGM

probes, but the critically small sample size limits confidence in

cosmological inferences. The requisite unobscured sightlines to high-z

are extremely rare, but SDSS provides 5800, z>3.1 QSOs potentially

suitable for HeII studies. We've cross-correlated SDSS quasars with

GALEX UV sources to obtain dozens of new, high confidence, candidate

sightlines {z=3.1-4.9} potentially useful for detailed HeII studies with

HST. We propose brief, 2-orbit reconnaissance ACS SBC prism exposures

toward each of the best dozen new quasars, to definitively verify UV

flux down to HeII. Our combined SDSS/GALEX selection insures a high

confirmation rate, as the quasars are already known to be UV bright in

GALEX. Our program will provide a statistical sample of HeII sightlines

extending to high redshift, enabling future long exposure follow-up

spectra with the SBC prism, or superb quality COS or STIS spectra after

SM4. Stacks of our prism spectra will also directly yield ensemble

information. Ultimately, the new sightlines will enable confident

measures of the spectrum and evolution of the ionizing background, the

evolution of HeII opacity, the epoch of helium reionization, and the

density of IGM baryons.

FGS 11317

HST Cycle 16 & pre-SM4 FGS alignment check

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 i

mages. Each observation will need its own CRMAP, as different SAA

passages leave different imprints on the NICMOS detectors.

NIC2/NIC1 11000

Evaporating Disks

Evaporation in the vicinity of an O star disrupts protoplanetary disks,

as seen in the Orion proplyds. We have found a number of evaporating

disks with Spitzer, which are in some ways more dramatic and better

oriented for detailed study than the proplyds ? they have cometary tails

extending up to 0.1 pc from the evaporation working surface. We will use

Spitzer/IRS and HST/NICMOS to investigate these systems in more detail.

We want to explore the excitation condition in the gas, both in the head

and in the tail where possible. We will measure the effects of

evaporation on the characteristic emission features of the dust. We also

will use NICMOS to image them in detail, including mapping complex

structures resolved in their tails at 24 microns

WFPC2 10884

The Dynamical Structure of Ellipticals in the Coma and Abell 262

Clusters

We propose to obtain images of 13 relatively luminous early type

galaxies in the Coma cluster and Abell 262 for which we have already

collected ground based major and minor axis spectra and images. The

higher resolution HST images will enable us to study the central regions

of these galaxies which is crucial to our dynamical modeling. The

complete data set will allow us to perform a full dynamical analysis and

to derive the dark matter content and distribution, the stellar orbital

structure, and the stellar population properties of these objects,

probing the predictions of galaxy formation models. The dynamical

analysis will be performed using an up-to-date axi-symmetric orbit

superposition code.

WFPC2 10915

ACS Nearby Galaxy Survey

Existing HST observations of nearby galaxies comprise a sparse and

highly non-uniform archive, making comprehensive comparative studies

among galaxies essentially impossible. We propose to secure HST's

lasting impact on the study of nearby galaxies by undertaking a

systematic, complete, and carefully crafted imaging survey of ALL

galaxies in the Local Universe outside the Local Group. The resulting

images will allow unprecedented measurements of: {1} the star formation

history {SFH} of a >100 Mpc^3 volume of the Universe with a time

resolution of Delta[log{t}]=0.25; {2} correlations between spatially

resolved SFHs and environment; {3} the structure and properties of thick

disks and stellar halos; and {4} the color distributions, sizes, and

specific frequencies of globular and disk clusters as a function of

galaxy mass and environment. To reach these goals, we will use a

combination of wide-field tiling and pointed deep imaging to obtain

uniform data on all 72 galaxies within a volume-limited sample extending

to ~3.5 Mpc, with an extension to the M81 group. For each galaxy, the

wide-field imaging will cover out to ~1.5 times the optical radius and

will reach photometric depths of at least 2 magnitudes below the tip of

the red giant branch throughout the limits of the survey volume. One

additional deep pointing per galaxy will reach SNR~10 for red clump

stars, sufficient to recover the ancient SFH from the color-magnitude

diagram. This proposal will produce photometric information for ~100

million stars {comparable to the number in the SDSS survey} and uniform

multi- color images of half a square degree of sky. The resulting

archive will establish the fundamental optical database for nearby

galaxies, in preparation for the shift of high- resolution imaging to

the near-infrared.

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:

18163-2 - RMGA Calibration for December 2007

COMPLETED OPS NOTES: (None)

                       SCHEDULED      SUCCESSFUL   

FGS GSacq               11                  11                           

FGS REacq               05                  05                               

OBAD with Maneuver 32                  32                    

SIGNIFICANT EVENTS:

OPS Request 18163 was successfully executed on December 13, 2007 to

perform an RMGA Calibration test. RMGA was powered on at GMT 347/22:00.

PSEA testmode was executed from GMT 347/23:12 to 347/23:42 to collect

RMGA analog drift rate data for bias estimates. This data collection

period was about 30 minutes (15 iterations of PSEA testmode) and will be

processed by SAC. Assessment will determine if the drift rates have

changed enough to warrant a bias update in PSEA configuration memory.