Daily Report # 4327

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)