Daily Report # 4345

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 # 4345

PERIOD COVERED: UT April 19, 2007 (DOY 109)

OBSERVATIONS SCHEDULED

WFPC2 10877

A Snapshot Survey of the Sites of Recent, Nearby Supernovae

During the past few years, robotic {or nearly robotic} searches for
supernovae {SNe}, most notably our Lick Observatory Supernova Search {LOSS},
have found hundreds of SNe, many of them in quite nearby galaxies {cz 4000
km/s}. Most of the objects were discovered before maximum brightness, and
have follow-up photometry and spectroscopy; they include some of the
best-studied SNe to date. We propose to conduct a snapshot imaging survey of
the sites of some of these nearby objects, to obtain late-time photometry
that {through the shape of the light and color curves} will help reveal the
origin of their lingering energy. The images will also provide
high-resolution information on the local environments of SNe that are far
superior to what we can procure from the ground. For example, we will obtain
color-color and color-magnitude diagrams of stars in these SN sites, to
determine the SN progenitor masses and constraints on the reddening.
Recovery of the SNe in the new HST images will also allow us to actually
pinpoint their progenitor stars in cases where pre- explosion images exist
in the HST archive. This proposal is an extension of our successful Cycle 13
snapshot survey with ACS. It is complementary to our Cycle 15 archival
proposal, which is a continuation of our long-standing program to use
existing HST images to glean information about SN environments.

WFPC2 10809

The nature of "dry" mergers in the nearby Universe

Recent studies have shown that "dry" mergers of red, bulge-dominated
galaxies at low redshift play an important role in shaping today's most
massive ellipticals. These mergers have been identified in extremely deep
ground-based images of red sequence galaxies at z ~ 0.1. The ground-based
images reach surface brightness limits of AB ~ 29, but lack the resolution
to study the morphologies of the galaxies inside the effective radius. Here
we propose to obtain ACS images of a representative sample of 40 of these
red sequence galaxies: 15 ongoing dry mergers, 15 remnants, and 10
undisturbed objects. We will measure the isophote shapes and ellipticities
of the galaxies, their dust content, morphological fine structure {shells
and ripples}, AGN content, and their location on the Fundamental Plane. By
comparing galaxies in different stages of the merging process we can
constrain the amount of gas associated with these red mergers, the effect of
active nuclei, and track structural changes. As two galaxies can be observed
in a single orbit 20 orbits are requested to observe the 40 galaxies.

WFPC2 10829

Secular Evolution at the End of the Hubble Sequence

The bulgeless disk galaxies at the end of the Hubble Sequence evolve at a
glacial pace relative to their more violent, earlier-type cousins. The
causes of their internal, or secular evolution are important because secular
evolution represents the future fate of all galaxies in our accelerating
Universe and is a key ingredient to understanding galaxy evolution in
lower-density environments at present. The rate of secular evolution is
largely determined by the stability of the cold ISM against collapse, star
formation, and the buildup of a central bulge. Key diagnostics of the ISM's
stability are the presence of compact molecular clouds and narrow dust
lanes. Surprisingly, edge-on, pure disk galaxies with circular velocities
below 120 km/s do not appear to contain such dust lanes. We propose to
obtain ACS/WFC F606W images of a well-selected sample of extremely late-type
disk galaxies to measure the characteristic scale size of the cold ISM and
determine if they possess the unstable, cold ISM necessary to drive secular
evolution. Our sample has been carefully constructed to include disk
galaxies above and below the critical circular velocity of 120 km/s where
the dust properties of edge-on disks change so remarkably. We will then use
surface brightness profiles to search for nuclear star clusters and
pseudobulges, which are early indicators that secular evolution is at work,
as well as measure the pitch angle of the dust lanes as a function of radius
to estimate the central mass concentrations.

FGS 10931

Dynamical Masses and Radii of Four White Dwarf Stars

We will use FGS1R in its high angular resolution observing mode (TRANS) to
resolve the white dwarf binary systems. Each exposure will be comprised of
about 20 scans. The interferograms derived from each scan will be cross-
correlated and co-added to yield a high SNR. To further surpress the noise
(these targets are near the FGS's faint limiting magnitude), the co-added
inteferograms will be carefully smoothed by being represented as a
piece-wise We will use FGS1R in its high angular resolution observing mode
(TRANS) to resolve the white dwarf binary systems. Each exposure will be
comprised of about 20 scans. The interferograms derived from each scan will
be cross-correlated and co-added to yield a high SNR. To further surpress
the noise(these targets are near the FGS's faint limiting magnitude), the
co-added inteferograms will be carefully smoothed by being represented as a
piece-wise smooth segmanted polynomial. These observations will yield the
separation and position angle of the binary components, as well as the
brightness of each. In addition, the binary and field stars simultaneously
in the FGS FOV will be observed in POS mode to accurately determine the
relative positions of the stars. This will facilitate the construction of an
inertial reference frame for the binary, thereby allowing the relative orbit
that will be ultimately determined from the TRANS data to be converted into
a physical orbit. This will allow us to determine the relative mass of each
white dwarf in the binarty system. In addition, the POS mode data will give
the proper motion and parallax of the binary, which will allow us to compute
the mass and radius of each white dwarf.

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 images. Each observation will need its own CRMAP, as
different SAA passages leave different imprints on the NICMOS detectors.

NIC3 10792

Quasars at Redshift z=6 and Early Star Formation History

We propose to observe four high-redshift quasars {z=6} in the NIR in order
to estimate relative Fe/Mg abundances and the central black hole mass. The
results of this study will critically constrain models of joint quasar and
galaxy formation, early star formation, and the growth of supermassive black
holes. Different time scales and yields for alpha-elements {like O or Mg}
and for iron result into an iron enrichment delay of ~0.3 to 0.6 Gyr. Hence,
despite the well-known complexity of the FeII emission line spectrum, the
ratio iron/alpha - element is a potentially useful cosmological clock. The
central black hole mass will be estimated based on a recently revised back
hole mass - luminosity relationship. The time delay of the iron enrichment
and the time required to form a supermassive black hole {logM8 Msol, tau
~0.5Gyr} as evidenced by quasar activity will be used to date the beginning
of the first intense star formation, marking the formation of the first
massive galaxies that host luminous quasars, and to constrain the epoch when
supermassive black holes start to grow by accretion.

WFPC2 10890

Morphologies of the Most Extreme High-Redshift Mid-IR-Luminous Galaxies

The formative phase of the most massive galaxies may be extremely luminous,
characterized by intense star- and AGN-formation. Till now, few such
galaxies have been unambiguously identified at high redshift, restricting us
to the study of low-redshift ultraluminous infrared galaxies as possible
analogs. We have recently discovered a sample of objects which may indeed
represent this early phase in galaxy formation, and are undertaking an
extensive multiwavelength study of this population. These objects are bright
at mid-IR wavelengths {F[24um]0.8mJy}, but deep ground based imaging
suggests extremely faint {and in some cases extended} optical counterparts
{R~24-27}. Deep K-band images show barely resolved galaxies. Mid-infrared
spectroscopy with Spitzer/IRS reveals that they have redshifts z ~ 2-2.5,
suggesting bolometric luminosities ~10^{13-14}Lsun! We propose to obtain
deep ACS F814W and NIC2 F160W images of these sources and their environs in
order to determine kpc-scale morphologies and surface photometry for these
galaxies. The proposed observations will help us determine whether these
extreme objects are merging systems, massive obscured starbursts {with
obscuration on kpc scales!} or very reddened {locally obscured} AGN hosted
by intrinsically low-luminosity galaxies.

WFPC2 11083

The Structure, Formation and Evolution of Galactic Cores and Nuclei

A surprising result has emerged from the ACS Virgo Cluster Survey {ACSVCS},
a program to obtain ACS/WFC gz imaging for a large, unbiased sample of 100
early-type galaxies in the Virgo Cluster. On subarcsecond scales {i.e.,
0.1"-1"}, the HST brightness profiles vary systematically from the
brightest giants {which have nearly constant surface brightness cores} to
the faintest dwarfs {which have compact stellar nuclei}. Remarkably, the
fraction of galaxy mass contributed by the nuclei in the faint galaxies is
identical to that contributed by supermassive black holes in the bright
galaxies {0.2%}. These findings strongly suggest that a single mechanism is
responsible for both types of Central Massive Object: most likely internally
or externally modulated gas inflows that feed central black holes or lead to
the formation of "nuclear star clusters". Understanding the history of gas
accretion, star formation and chemical enrichment on subarcsecond scales has
thus emerged as the single most pressing question in the study of nearby
galactic nuclei, either active or quiescent. We propose an ambitious HST
program {199 orbits} that constitutes the next, obvious step forward:
high-resolution, ultraviolet {WFPC2/F255W} and infrared {NIC1/F160W} imaging
for the complete ACSVCS sample. By capitalizing on HST's unique ability to
provide high-resolution images with a sharp and stable PSF at UV and IR
wavelengths, we will leverage the existing optical HST data to obtain the
most complete picture currently possible for the history of star formation
and chemical enrichment on these small scales. Equally important, this
program will lead to a significant improvement in the measured structural
parameters and density distributions for the stellar nuclei and the
underlying galaxies, and provide a sensitive measure of "frosting" by young
stars in the galaxy cores. By virtue of its superb image quality and stable
PSF, NICMOS is the sole instrument capable of the IR observations proposed
here. In the case of the WFPC2 observations, high-resolution UV imaging {
0.1"} is a capability unique to HST, yet one that could be lost at any any
time.

FLIGHT OPERATIONS SUMMARY:

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

HSTARS:

10781 - GSAcq(1,3,1) was not attempted due to prior M2G entry

GSacq(1,3,1) scheduled at 109/15:24:49 - 15:32:54 was not attempted.

Open loop period(s), following the second of a pair of OBADs resulted in
unplanned M2G entry. OBAD2 had (RSS) value of 120.38 arcseconds. Because the
OBAD2 was reset, the acquisition was not attempted. Post-acquisition
OBAD/MAP had (RSS) value of 2130.60 arcseconds.

10782 - GSacq (1,2,2) loss of lock

During LOS GSacq(1,2,2) scheduled at 110/04:22:51 loss lock. At
AOS(04:50:02) stop flags QF1STOPF and QSTOP were flagging.

COMPLETED OPS REQUEST:

10837-3 - HMSS/CSS KF Initialization Convergence
18041-0 - Preview KF Sun Vector data via TMDiags
17597-7 - FHST Stuck-on-Bottom Macro Execution

COMPLETED OPS NOTES: (None)

SIGNIFICANT EVENTS:

Flish Report

The Kalman Filter was restarted at 109/21:48 during orbit day and during an
M2G guiding interval. The filter was activated with the default
configuration of MSS and CSS sensor inputs enabled. All UKF parameters
showed nominal convergence and steady-state operation. The test was an
MSS/CSS Initialization Test Case with the spacecraft inertially fixed during
a slow changing B-field in orbit day (M_C_INS, Test #8). The Kalman Filter
was restarted at 109/23:34 during orbit day, an M2G guiding interval and a
large vehicle slew. The filter was activated with the default configuration
of MSS and CSS sensor inputs enabled. All UKF parameters showed nominal
convergence and steady-state operation. The test was an MSS/CSS
Initialization Test Case with the spacecraft maneuvering during a slow
changing B-field in orbit day (M_C_IVS, Test #6). This completes the KF OOT
testing for this week.