Daily # 4233

HUBBLE SPACE TELESCOPE - Continuing to collect World Class Science

DAILY REPORT # 4233

PERIOD COVERED: UT November 02, 2006 (DOY 306)

OBSERVATIONS SCHEDULED

ACS/HRC 10556

Neutral Gas at Redshift z=0.5

Damped Lyman-alpha systems {DLAs} are used to track the bulk of the
neutral hydrogen gas in the Universe. Prior to HST UV spectroscopy,
they could only be studied from the ground at redshifts z1.65.
However, HST has now permitted us to discover 41 DLAs at z1.65 in our
previous surveys. Followup studies of these systems are providing a
wealth of information about the evolution of the neutral gas phase
component of the Universe. But one problem is that these 41
low-redshift systems are spread over a wide range of redshifts
spanning nearly 70% of the age of the Universe. Consequently, past
surveys for low-redshift DLAs have not been able to offer very good
precision in any small redshift regime. Here we propose an ACS-HRC-
PR200L spectroscopic survey in the redshift interval z=[0.37, 0.7]
which we estimate will permit us to discover another 41 DLAs. This
will not only allow us to double the number of low-redshift DLAs, but
it will also provide a relatively high-precision regime in the
low-redshift Universe that can be used to anchor evolutionary studies.
Fortunately DLAs have high absorption equivalent width, so
ACS-HRC-PR200L has high-enough resoultion to perform this proposed
MgII-selected DLA survey.

ACS/HRC 10860

The largest Kuiper belt object

The past year has seen an explosion in the discoveries of Pluto-sized
objects in the Kuiper belt. With the discoveries of the
methane-covered 2003 UB313 and 2005 FY9, the multiple satellite system
of 2003 EL61, and the Pluto-Charon analog system of Orcus and its
satellite, it is finally apparent that Pluto is not a unique oddball
at the edge of the solar system, but rather one of a family of
similarly large objects in the Kuiper belt and beyond. HST
observations over the past decade have been critical for understanding
the interior, surface, and atmosphere of Pluto and Charon. We propose
here a comprehensive series of observations designed to similarly
expand our knowledge of these recently discovered Pluto-sized and
near-Pluto-sized Kuiper belt objects. These observations will measure
objects' sizes and densities, explore the outcome of collisions in the
outer solar system, and allow the first ever look at the interior
structure of a Kuiper belt object. Our wide field survey that
discovered all of these objects is nearly finished, so after five
years of continuous searching we are finally almost complete in our
tally of these near-Pluto-sized objects. This large HST request is the
culmination of this half-decade search for new planetary-sized
objects. As has been demonstrated repeatedly by the approximately 100
previous orbits devoted to the study of Pluto, only HST has the
resolution and sensitivity for detailed study of these distant
objects.

ACS/WFC 10843

Deep Imaging of Extremely Metal-Poor Galaxies

Conflicting evidence exists regarding whether the most metal-poor and
actively star-forming galaxies in the local universe such as I Zw 18
contain evolved stars. We propose to help settle this issue by
obtaining deep ACS/HRC U, narrow-V, I, and H-alpha images of nine
nearby {z 0.01} extremely metal-poor {12 + O/H 7.65} galaxies
selected from the Sloan Digital Sky Survey. These objects are only
marginally resolved from the ground and appear uniformly blue,
strongly motivating HST imaging. The continuum images will establish:
1.} If underlying populations of evolved stars are present, by
revealing the objects' colors on scales ~10 pc, and 2.} The presence
of any faint tidal features, dust lanes, and globular or super star
clusters, all of which constrain the objects' evolutionary states. The
H-alpha images, in combination with ground-based echelle spectroscopy,
will reveal 1.} Whether the objects are producing "superwinds" that
are depleting them of their metals; ground-based images of some of
them indeed show large halos of ionized gas, and 2.} The
correspondence of their nebular and stellar emission on scales of a
few parsecs, which is important for understanding the "feedback"
process by which supernovae and stellar winds regulate star formation.
One of the sample objects, CGCG 269-049, lies only ~2 Mpc away,
allowing the detection of individual red giant stars in it if any are
present. We have recently obtained Spitzer images and spectra of this
galaxy to determine its dust content and star formation history, which
will complement the proposed HST observations.

ACS/WFC 10886

The Sloan Lens ACS Survey: Towards 100 New Strong Lenses

As a continuation of the highly successful Sloan Lens ACS {SLACS}
Survey for new strong gravitational lenses, we propose one orbit of
ACS-WFC F814W imaging for each of 50 high- probability strong
galaxy-galaxy lens candidates. These observations will confirm new
lens systems and permit immediate and accurate photometry, shape
measurement, and mass modeling of the lens galaxies. The lenses
delivered by the SLACS Survey all show extended source structure,
furnishing more constraints on the projected lens potential than
lensed-quasar image positions. In addition, SLACS lenses have lens
galaxies that are much brighter than their lensed sources,
facilitating detailed photometric and dynamical observation of the
former. When confirmed lenses from this proposal are combined with
lenses discovered by SLACS in Cycles 13 and 14, we expect the final
SLACS lens sample to number 80--100: an approximate doubling of the
number of known galaxy-scale strong gravitational lenses and an
order-of-magnitude increase in the number of optical Einstein rings.
By virtue of its homogeneous selection and sheer size, the SLACS
sample will allow an unprecedented exploration of the mass structure
of the early-type galaxy population as a function of all other
observable quantities. This new sample will be a valuable resource to
the astronomical community by enabling qualitatively new strong
lensing science, and as such we will waive all but a short {3-month}
proprietary period on the observations.

ACS/WFC 10911

Calibration of ACS F814W Surface Brightness Fluctuations

The surface brightness fluctuations {SBF} method has emerged as the
primary distance indicator for mapping local large-scale structures
{Virgo, Fornax}, as well as the velocity field out to nearly 15,000
km/s {z 0.05}. This is because other precision distance indicators
either lack the requisite depth {Cepheids, TRGB} or are too rare for
adequate sampling {supernovae}, while more traditional methods
{Tully-Fisher, fundamental plane} lack the necessary precision. The
SBF method is now being used with great success in several major ACS
Wide Field Camera programs. However, whereas the band of choice for
the nearby structure studies has been F850LP, for the distant
large-scale flow studies it is F814W because of its much greater
throughput. As a result, the current calibration for the more distant
studies is inadequate. We propose to establish the first systematic
calibration of the SBF method in the important F814W ACS WFC bandpass.
We will do this by measuring SBF in an optimized sample of galaxies in
the nearby compact Fornax cluster. Given the large amount of effort
and HST time being dedicated to F814W SBF measurements, it is
imperative that we correct this outstanding calibration problem while
time remains. For an extremely modest expenditure of orbits, we will
remove a significant systematic error and vastly improve the overall
accuracy of the ongoing ACS F814W SBF work. These data will also
greatly enhance the legacy value of the HST archive for future SBF
studies.

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.

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.

FLIGHT OPERATIONS SUMMARY:

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

HSTARS: (None)

COMPLETED OPS REQUEST: (None)

COMPLETED OPS NOTES: (None)

SCHEDULED SUCCESSFUL
FGS GSacq 09 09
FGS REacq 06 06
OBAD with Maneuver 32 32

SIGNIFICANT EVENTS: (None)