Daily # 4298

HUBBLE SPACE TELESCOPE - Continuing to collect World Class Science

DAILY REPORT # 4298

PERIOD COVERED: UT February 12, 2007 (DOY 043)

OBSERVATIONS SCHEDULED

NIC2 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.

WFPC2 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.

NIC1/NIC2/NIC3 8793

NICMOS Post-SAA calibration - CR Persistence Part 4

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 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.

WFPC2 10913

The Light Echoes around V838 Monocerotis

V838 Monocerotis, which burst upon the astronomical scene in early
2002, is a completely unanticipated new object. It underwent a
large-amplitude and very luminous outburst, during which its spectrum
remained that of an extremely cool supergiant. A rapidly evolving set
of light echoes around V838 Mon was discovered soon after the
outburst, and quickly became the most spectacular display of the
phenomenon ever seen. These light echoes provide the means to
accomplish four unique types of measurements based on continued HST
imaging during the event: {1} Study effects of MHD turbulence at high
resolution and in 3 dimensions; {2} Construct the first unambiguous
and fully 3-D map of a circumstellar dust envelope in the Milky Way;
{3} Study dust physics in a unique setting where the spectrum and
light curve of the illumination, and the scattering angle, are
unambiguously known; and {4} Determine the distance to V838 Mon
through direct geometric techniques. Because of the extreme rarity of
light echoes, this is almost certainly the only opportunity to achieve
such results during the lifetime of HST. We propose two visits during
Cycle 15, in order to continue the mapping of the circumstellar dust
and to achieve the other goals listed above.

WFPC2 11095

Hubble Heritage Observations of NGC 6050

The Hubble Heritage team will use a single pointing of WFPC2 to obtain
F450W, F555W, F656N, and F814W images of NGC 6050 as part of a public
release image.

FLIGHT OPERATIONS SUMMARY:

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

HSTARS:

10684 - GSacq(2,3,3) resulted in Fine Lock Backup

GSacq(2,3,3) scheduled at 043/15:18:56 resulted in Fine Lock Backup
(2,0,2). Stop flags QF3STOPF and QSTOP were received for FGS 3. OBAD2
at 1513:40 showed errors of V1= -1.15, V2=-2.29, V3=5.64 and RSS=6.19.
The Map at 15:26:04 showed error of V1=-0.76, V2=-12.39, V3=-2.54 and
RSS =12.67.

10685 - OBAD Failed Identification

At 043/18:29:14 OBAD1 scheduled at 18:26:19 failed. The second OBAD
and the Reacq was successful.

10686 - OBAD Failed Identification

At 043/23:36:38, OBAD1 using trackers FHST-1 and FHST-2 failed. OBAD
success flag (mnemonic GCHACL09) returned to the "no success" state (a
value of 1). OBAD1 had (RSS) value of 192464.25 arcseconds. Subsequent
GSAcq was successful.

COMPLETED OPS REQUEST: (None)

COMPLETED OPS NOTES: (None)

SCHEDULED SUCCESSFUL

FGS GSacq 07 07
FGS REacq 07 07
OBAD with Maneuver 28 26

SIGNIFICANT EVENTS: (None)