Daily # 4269

HUBBLE SPACE TELESCOPE - Continuing to collect World Class Science

DAILY REPORT # 4269

PERIOD COVERED: UT December 28, 2006 (DOY 362)

OBSERVATIONS SCHEDULED

ACS/HRC 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.

ACS/WFC 10813

MgII Absorption Line Systems: Galaxy Halos or the Metal-Enriched IGM?

MgII QSO absorption lines detected in the spectra of background QSOs
were used over a decade ago to infer that all redshift z 0.2
galaxies have gaseous halos of radius ~ 60 kpc. The actual size of the
halo was believed to be proportional to the luminosity of the galaxy.
However, these conclusions are now much harder to understand in light
of the results from numerical simulations which show how gas evolves
in the universe. These models predict that gas and galaxies merely
share the same filamentary structures defined by dark matter. If these
models are correct, how are MgII systems and galaxies really related?
We can better understand the distribution of absorbing gas if we FIRST
select galaxies close to QSO sightlines and THEN search for MgII
absorption at the redshift of the intervening galaxies. This is the
antithesis of the original experiments which sought to find absorbing
galaxies based on known MgII systems. The frequency with which we
detect MgII lines from randomly selected galaxies should enable us to
better understand if absorption arises in the halos of individual
galaxies, or if MgII merely arises in the same IGM that galaxies
inhabit. We have used ground-based telescopes to indentify twenty z =
0.31-0.55 galaxies within 14-51 kpc of a g 20 QSO, and to search for
MgII absorption at the galaxies' redshifts. Surprisingly, we find that
only 50% of our QSOs show MgII absorption. In this proposal, we seek
multi-color ACS images of twelve of the fields to i} correlate the
incidence of MgII with galaxy morphology; ii} determine if absorption
{or lack thereof} is related to galaxy disks or halos; iii} search for
signs of galaxy interactions which may explain the large
cross-sections of MgII systems; and iv} look for faint interloping
galaxies closer to the line of sight than the one we identified. An
important component of the program is to observe each field in the
SDSS g-, r- and i-bands, to permit an estimate of the photometric
redshift of any objects which lie closer to the QSO sightline than the
identified galaxy, and which might actually be responsible for the
absorption.

ACS/WFC 10918

Reducing Systematic Errors on the Hubble Constant: Metallicity
Calibration of the Cepheid PL Relation

Reducing the systematic errors on the Hubble constant is still of
significance and of immediate importance to modern cosmology. One of
the largest remaining uncertainties in the Cepheid- based distance
scale {which itself is at the foundation of the HST Key Project
determination of H_o} which can now be addressed directly by HST, is
the effect of metallicity on the Cepheid Period-Luminosity relation.
Three chemically distinct regions in M101 will be used to directly
measure and thereby calibrate the change in zero point of the Cepheid
PL relation over a range of metallicities that run from SMC-like,
through Solar, to metallicities as high as the most metal- enriched
galaxies in the pure Hubble flow. ACS for the first time offers the
opportunity to make a precise calibration of this effect which
currently accounts for at least a third of the total systematic
uncertainty on Ho. The calibration will be made in the V and I
bandpasses so as to be immediately and directly applicable to the
entire HST Cepheid-based distance scale sample, and most especially to
the highest-metallicity galaxies that were hosts to the Type Ia
supernovae, which were then used to extend the the distance scale
calibration out to cosmologically significant distances.

ACS/WFC/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.

NIC1 10797

HE0450-2958: Lonesome black hole, scantly dressed quasar or massively
dust obscured host galaxy?

We propose to obtain a deep NICMOS image of the bright z=0.285 quasar
HE0450-2958 that has an exceptional, undetected host galaxy, at least
6 times fainter than expected for the quasar luminosity. Several
mutually exclusive explanations that were put forward in the last
weeks, attempting to explain the apparently undermassive host galaxy,
have important implication for their respective areas: The host could
be a dust obscured ultra-luminous infrared galaxy in transition to
become a quasar, HE450-2958 could have a normal host galaxy but an
undermassive central black hole, or the quasar could recently have
been ejected from a nearby companion galaxy in a 3-body black hole
interaction or by gravitational recoil. We want to use NIC2 with the
minimum-background F160W filter to obtain a =10 times fainter limit
on the host galaxy mass than is currently available with ACS, in order
to set strong constraints for these very important scenarios.

NIC1/NIC2/NIC3 8794

NICMOS Post-SAA calibration - CR Persistence Part 5

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

NIC2, ACS/WFC 10802

SHOES-Supernovae, HO, for the Equation of State of Dark energy

The present uncertainty in the value of the Hubble constant {resulting
in an uncertainty in Omega_M} and the paucity of Type Ia supernovae at
redshifts exceeding 1 are now the leading obstacles to determining the
nature of dark energy. We propose a single, integrated set of
observations for Cycle 15 that will provide a 40% improvement in
constraints on dark energy. This program will observe known Cepheids
in six reliable hosts of Type Ia supernovae with NICMOS, reducing the
uncertainty in H_0 by a factor of two because of the smaller
dispersion along the instability strip, the diminished extinction, and
the weaker metallicity dependence in the infrared. In parallel with
ACS, at the same time the NICMOS observations are underway, we will
discover and follow a sample of Type Ia supernovae at z 1. Together,
these measurements, along with prior constraints from WMAP, will
provide a great improvement in HST's ability to distinguish between a
static, cosmological constant and dynamical dark energy. The Hubble
Space Telescope is the only instrument in the world that can make
these IR measurements of Cepheids beyond the Local Group, and it is
the only telescope in the world that can be used to find and follow
supernovae at z 1. Our program exploits both of these unique
capabilities of HST to learn more about one of the greatest mysteries
in science.

FLIGHT OPERATIONS SUMMARY:

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

HSTARS:

10581 - OBAD Failed

During LOS OBAD2 scheduled at 362/10:40:16 failed. At AOS 10:58:00 ESB
1903(OBAD Failed Quaternion) was observed.

10583 - GSACQ(2,1,2) fine lock backup on FGS 2

GSACQ(2,1,2) at 362/22:34:47 acquired in fine lock backup on FGS 2
only, with QF1STOPF and QSTOP flags set on FGS 1. No other flags were
seen. Vehicle was LOS at time of failure.

COMPLETED OPS REQUEST: (None)

COMPLETED OPS NOTES: (None)

SCHEDULED SUCCESSFUL
FGS GSacq 11 11
FGS REacq 02 02
OBAD with Maneuver 26 25

SIGNIFICANT EVENTS: (None)