Notice: For the foreseeable future, the daily reports may contain

apparent discrepancies between some proposal descriptions and the listed

instrument usage. This is due to the conversion of previously approved

ACS WFC or HRC observations into WFPC2, or NICMOS observations

subsequent to the loss of ACS CCD science capability in late January.

HUBBLE SPACE TELESCOPE - Continuing to collect World Class Science

DAILY REPORT      # 4327

PERIOD COVERED: UT March 26, 2007 (DOY 085)

OBSERVATIONS SCHEDULED

WFPC2 10798

Dark Halos and Substructure from Arcs & Einstein Rings

The surface brightness distribution of extended gravitationally lensed

arcs and Einstein rings contains super-resolved information about the

lensed object, and, more excitingly, about the smooth and clumpy mass

distribution of the lens galaxies. The source and lens information can

non-parametrically be separated, resulting in a direct "gravitational

image" of the inner mass-distribution of cosmologically-distant galaxies

{Koopmans 2005; Koopmans et al. 2006 [astro-ph/0601628]}. With this goal

in mind, we propose deep HST ACS-F555W/F814W and NICMOS-F160W WFC

imaging of 20 new gravitational-lens systems with spatially resolved

lensed sources, of the 35 new lens systems discovered by the Sloan Lens

ACS Survey {Bolton et al. 2005} so far, 15 of which are being imaged in

Cycle-14. Each system has been selected from the SDSS and confirmed in

two time- efficient HST-ACS snapshot programs {cycle 13&14}.

High-fidelity multi-color HST images are required {not delivered by the

420s snapshots} to isolate these lensed images {properly cleaned,

dithered and extinction-corrected} from the lens galaxy surface

brightness distribution, and apply our "gravitational maging" technique.

Our sample of 35 early-type lens galaxies to date is by far the largest,

still growing, and most uniformly selected. This minimizes selection

biases and small-number statistics, compared to smaller, often

serendipitously discovered, samples. Moreover, using the WFC provides

information on the field around the lens, higher S/N and a better

understood PSF, compared with the HRC, and one retains high spatial

resolution through drizzling. The sample of galaxy mass distributions -

determined through this method from the arcs and Einstein ring HST

images - will be studied to: {i} measure the smooth mass distribution of

the lens galaxies {dark and luminous mass are separated using the HST

images and the stellar M/L values derived from a joint stellar-dynamical

analysis of each system}; {ii} quantify statistically and individually

the incidence of mass-substructure {with or without obvious luminous

counter- parts such as dwarf galaxies}. Since dark-matter substructure

could be more prevalent at higher redshift, both results provide a

direct test of this prediction of the CDM hierarchical

structure-formation model.

NIC1/NIC2/NIC3 8795

NICMOS Post-SAA calibration - CR Persistence Part 6

A new proceedure proposed to alleviate the CR-persistence problem of

NICMOS. Dark frames will be obtained immediately upon exiting the SAA

contour 23, and everytime 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 10808

Morphologies of spectroscopically-confirmed "red and dead" galaxies at

z~2.5

Using a combination of wide-field near-infrared imaging and very deep

follow-up near-infrared spectroscopy we have identified a population of

massive "red and dead" galaxies at z~2.5. The galaxies lack emission

lines and have strong Balmer/4000 Angstrom breaks, demonstrating

directly that they have evolved stellar populations. These objects are

very likely progenitors of massive ellipticals today and may be

descendants of the first generation of galaxies. We propose to image 10

of these objects with the NIC2 camera to determine their morphologies.

The goals are to 1} determine whether they have the sizes of present-day

early-types or are more compact, as predicted by models, 2} determine

the morphology, using visual classification and quantitative methods,

and 3} constrain the evolution of the Kormendy relation from z~2.5 to

the present. These observations will show whether the oldest and most

massive galaxies at z~2.5 were already fully formed or still in the

process of assembly.

NIC3 11080

Exploring the Scaling Laws of Star Formation

As a variety of surveys of the local and distant Universe are

approaching a full census of galaxy populations, our attention needs to

turn towards understanding and quantifying the physical mechanisms that

trigger and regulate the large-scale star formation rates {SFRs} in

galaxies.

WFPC2 10845

HUNTING FOR OPTICAL COMPANIONS TO BINARY MILLISECOND PULSARS IN TERZAN 5

AND NGC6266

We propose deep WFPC2 and NICMOS observations to search for optical

companions to binary millisecond pulsar {MSPs} in two Globular Clusters

{GCs}: Terzan 5 and NGC6266. Terzan 5 has the largest MSP population of

any GC: 33 MSP {17 in binary systems} have been discovered up to now in

this stellar system. NGC6266 ranks fifth among the GC for wealth of MSPs

but it is the only one in which all the {six} detected MSPs are in

binary systems. Only 5 optical counterparts to binary MSP companions are

known in GCs {two of them have been discovered by our group}: hence even

the addition of a few new identifications are crucial to investigate the

variety of processes occurring in binary MSPs in dense environment. The

observations proposed here would easily double/triple the existing

sample of known MSP companions, allowing the first meaningful study of

the phenomena which drive the formation and evolution of these exotic

systems. Moreover, since most of binary MSP in GC are formed via stellar

interactions in the high density regions of the cluster, the

determination of the nature of the companion and the incidence of this

collisionally induced population have a significant impact on our

knowledge of the cluster dynamics. Even more interesting, the study of

the optical companions to NSs in a GC allows to derive tighter

constraints {than those obtainable for NS binaries in the galactic

field} on the properties {mass, orbital inclination and so on} of the

compation star. This has, in turn, an intrisic importance for

fundamental physics since it offers the opportunity of measuring the

mass of the NS and hence to put constraints to the equation of state of

matter at nuclear equilibrium density.

WFPC2 11030

WFPC2 WF4 Temperature Reduction #3

In the fall of 2005, a serious anomaly was found in images from the WF4

CCD in WFPC2. The WF4 CCD bias level appeared to have become unstable,

resulting in sporadic images with either low or zero bias level. The

severity and frequency of the problem was rapidly increasing, making it

possible that WF4 would soon become unusable if no work-around were

found. Examination of bias levels during periods with frequent WFPC2

images showed low and zero bias episodes every 4 to 6 hours. This

periodicity is driven by cycling of the WFPC2 Replacement Heater, with

the bias anomalies occurring at the temperature peaks. The other three

CCDs {PC1, WF2, and WF3} appear to be unaffected and continue to operate

properly. Lowering the Replacement Heater temperature set points by a

few degrees C effectively eliminates the WF4 anomaly. On 9 January 2006,

the upper set point of the WFPC2 Replacement Heater was reduced from

14.9C to 12.2C. On 20 February 2006, the upper set point was reduced

from 12.2C to 11.3C, and the lower set point was reduced from 10.9C to

10.0C. These changes restored the WF4 CCD bias level; however, the bias

level has begun to trend downwards again, mimicking its behavior in late

2004 and early 2005. A third temperature reduction is planned for March

2007. We will reduce the upper set point of the heater from 11.3C to

10.4C and the lower set point from 10.0C to 9.1C. The observations

described in this proposal will test the performance of WFPC2 before and

after this temperature reduction. Additional temperature reductions may

be needed in the future, depending on the performance of WF4. Orbits:

internal 26, external 1

WFPC2 11079

Treasury Imaging of Star Forming Regions in the Local Group:

Complementing the GALEX and NOAO Surveys

We propose to use WFPC2 to image the most interesting star-forming

regions in the Local Group galaxies, to resolve their young stellar

populations. We will use a set of filters including F170W, which is

critical to detect and characterize the most massive stars, to whose hot

temperatures colors at longer wavelengths are not sensitive. WFPC2's

field of view ideally matches the typical size of the star-forming

regions, and its spatial resolution allows us to measure indvidual

stars, given the proximity of these galaxies. The resulting H- R

diagrams will enable studies of star-formation properties in these

regions, which cover largely differing metallicities {a factor of 17,

compared to the factor of 4 explored so far} and characteristics. The

results will further our understanding of the star-formation process, of

the interplay between massive stars and environment, the properties of

dust, and will provide the key to interpret integrated measurements of

star-formation indicators {UV, IR, Halpha} available for several

hundreds more distant galaxies. Our recent deep surveys of these

galaxies with GALEX {FUV, NUV} and ground-based imaging {UBVRI, Halpha,

[OIII] and [SII]} provided the identification of the most relevant SF

sites. In addition to our scientific analysis, we will provide catalogs

of HST photometry in 6 bands, matched corollary ground-based data, and

UV, Halpha and IR integrated measurements of the associations, for

comparison of integrated star-formation indices to the resolved

populations. We envisage an EPO component.

FLIGHT OPERATIONS SUMMARY:

Significant Spacecraft Anomalies: (The following are preliminary reports

of potential non-nominal performance that will be investigated.)

HSTARS:

10755 - GSAcq (1,3,3) failed due to Search Radius Limit Exceeded on FGS 3

           At 085/21:04:10 GSAcq (1,3,3) scheduled from 21:00:52-21:08:07 failed

           due to search radius limit exceeded on FGS 3.

           OBAD #1 RSS: 1853.79

           OBAD #2 RSS: 3.23 OBAD

           MAP RSS: 2.65

           At 085/22:38:46 REAcq (1,3,3) scheduled from 22:35:35-22:42:50 failed

           due to search radius limit exceeded on FGS 3.

           OBAD #1 RSS: 807.48

           OBAD #2 RSS: 8.09 OBAD

           MAP RSS: 17.01

COMPLETED OPS REQUEST: (None)

COMPLETED OPS NOTES: (None)

                       SCHEDULED      SUCCESSFUL     

FGS GSacq               06                  05                          

FGS REacq               07                  06              

OBAD with Maneuver 26                  26                                  

SIGNIFICANT EVENTS: (None)