Daily Report #4636

HUBBLE SPACE TELESCOPE - Continuing to collect World Class Science

DAILY REPORT***** #4636

PERIOD COVERED: 5am June 19 - 5am June 20, 2008 (DOY
171/0900z-172/0900z)

OBSERVATIONS SCHEDULED

ACS/SBC 11215

New Sightlines for the Study of Intergalactic Helium: Dozens of
High-Confidence, UV-Bright Quasars from SDSS/GALEX

The reionization of IGM helium is thought to have occurred at
redshifts of z=3 to 4. Detailed study of HeII Lyman-alpha absorption
toward a handful of QSOs at 2.7z3.3 demonstrated the high potential
of such IGM probes, but the critically small sample size limits
confidence in cosmological inferences. The requisite unobscured
sightlines to high-z are extremely rare, but SDSS provides 5800, z3.1
QSOs potentially suitable for HeII studies. We've cross-correlated
SDSS quasars with GALEX UV sources to obtain dozens of new, high
confidence, candidate sightlines {z=3.1-4.9} potentially useful for
detailed HeII studies with HST. We propose brief, 2- orbit
reconnaissance ACS SBC prism exposures toward each of the best dozen
new quasars, to definitively verify UV flux down to HeII. Our combined
SDSS/GALEX selection insures a high confirmation rate, as the quasars
are already known to be UV bright in GALEX. Our program will provide a
statistical sample of HeII sightlines extending to high redshift,
enabling future long exposure follow-up spectra with the SBC prism, or
superb quality COS or STIS spectra after SM4. Stacks of our prism
spectra will also directly yield ensemble information. Ultimately, the
new sightlines will enable confident measures of the spectrum and
evolution of the ionizing background, the evolution of HeII opacity,
the epoch of helium reionization, and the density of IGM baryons.

NIC1/NIC2/NIC3 8795

NICMOS Post-SAA Calibration - CR Persistence Part 6

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/WFPC2 11192

NICMOS Confirmation of Candidates of the Most Luminous Galaxies at z 7

While the deepest pencil-beam near-IR survey suggested that the
Universe was too young to build up many luminous galaxies by z ~ 7--8
(Bouwens & Illingworth 2006), there is also evidenc indicating the
contrary. It is now known that some galaxies with stellar masses of
M1e10 Msun were already in place by z ~ 6--7, which strongly suggests
that their progenitors should be significantly more luminous, and
hence detectable in deep, wide-field near-IR surveys (Yan et al.
2006). As galaxies at such a high redshift should manifest themselves
as "dropouts" from the optical, we have carried out a very wide-field,
deep near-IR survey in the GOODS fields to search for z-band dropouts
as candidates of galaxies at z 7. In total, six promising candidates
have been found in ~ 300 sq. arcmin to J_AB ~ 24.5 mag (corresponding
to restframe M(UV) -22.5 mag at z ~ 7). By contrast, the galaxy
luminosity function (LF) suggested in BI06 would predict at most 3--5
galaxies over the entire 2-pi sky at this brightness level. Here we
propose to observe these candidates with NIC3 in F110W and F160W to
further investigate their nature. If any of these candidates are
indeed at z 7, the result will lead to a completely new picture of
star formation in the early universe. If none of our candidates are
consistent with being at z 7, then the depth and area of our near-IR
survey (from which the candidates are drawn) will let us set a very
stringent upper limit on the bright end of the galaxy LF at those
redshift. As a result, our program will still be able to provide new
clues about the processes of early galaxy formation, such as their
dust contents and their merging time scale (Yan et al. 2006).

WFPC2 11206

At the Cradle of the Milky Way: Formation of the Most Massive Field
Disk Galaxies at z1

We propose to obtain 2 orbit WFPC2 F814W images of a sample of the 15
most massive galaxies found at $1 z 1.3$. These were culled from
over 20,000 Keck spectra collected as part of DEEP and are unique
among high redshift massive galaxy samples in being kinematically
selected. Through a recent HST NICMOS-2 imaging program {GO-10532}, we
have confirmed that these galaxies have regular stellar disks, and
their emission line kinematics are not due to gradients from merging
components. These potentially very young galaxies are likely
precursors to massive local disks, assuming no further merging. The
proposed WFPC2 and existing NIC-2 data provide colors, stellar masses,
and ages of bulge and disk subcomponents, to assess whether old
stellar bulges and disks are in place at that time or still being
built, and constrain their formation epochs. Finally, this sample will
yield the first statistically significant results on the $z 1$
evolution of the size-velocity-luminosity scaling relations, for
massive galaxies at different wavelengths, and constrain whether this
evolution reflects stellar mass growth, or passive evolution, of
either bulge or disk components.

WFPC2 11218

Snapshot Survey for Planetary Nebulae in Globular Clusters of the
Local Group

Planetary nebulae {PNe} in globular clusters {GCs} raise a number of
interesting issues related to stellar and galactic evolution. The
number of PNe known in Milky Way GCs, 4, is surprisingly low if one
assumes that all stars pass through a PN stage. However, it is likely
that the remnants of stars now evolving in Galactic GCs leave the AGB
so slowly that any ejected nebula dissipates long before the star
becomes hot enough to ionize it. Thus there should not be ANY PNe in
Milky Way GCs--but there are four! It has been suggested that these
PNe are the result of mergers of binary stars within GCs, i.e., that
they are descendants of blue stragglers. The frequency of occurrence
of PNe in external galaxies poses more questions, because it shows a
range of almost an order of magnitude. I propose a Snapshot survey
aimed at discovering PNe in the GC systems of Local Group galaxies
more distant than the Magellanic Clouds. These clusters, some of which
may be much younger than their counterparts in the Milky Way, might
contain many more PNe than those of our own galaxy. I will use the
standard technique of emission-line and continuum imaging, which
easily discloses PNe.

WFPC2/NIC3/ACS/SBC 11144

Building on the Significant NICMOS Investment in GOODS: A Bright,
Wide-Area Search for z=7 Galaxies

One of the most exciting frontiers in observational cosmology has been
to trace the buildup and evolution of galaxies from very early times.
While hierarchical theory teaches us that the star formation rate in
galaxies likely starts out small and builds up gradually, only
recently has it been possible to see evidence for this observationally
through the evolution of the LF from z~6 to z~3. Establishing that
this build up occurs from even earlier times {z~7-8} has been
difficult, however, due to the small size of current high-redshift
z~7-8 samples -- now numbering in the range of ~4-10 sources.
Expanding the size of these samples is absolutely essential, if we
are to push current studies of galaxy buildup back to even earlier times.
Fortunately, we should soon be able to do so, thanks to ~50 arcmin**2
of deep {26.9 AB mag at 5 sigma} NICMOS 1.6 micron data that will be
available over the two ACS GOODS fields as a result of one recent 180-
orbit ACS backup program and a smaller program. These data will nearly
triple the deep near-IR imaging currently available and represent a
significant resource for finding and characterizing the brightest
high-redshift sources -- since high-redshift candidates can be easily
identified in these data from their red z-H colours. Unfortunately,
the red z-H colours of these candidates are not sufficient to
determine that these sources are at z=7, and it is important also to
have deep photometry at 1.1 microns. To obtain this crucial
information, we propose to follow up each of these z-H dropouts with
NICMOS at 1.1 microns to determine which are at high redshift and thus
significantly expand our sample of luminous, z=7 galaxies. Since
preliminary studies indicate that these candidates occur in only 30%
of the NIC3 fields, our follow-up strategy is ~3 times as efficient as
without this preselection and 9 times as efficient as a search in a
field with no pre-existing data. In total, we expect to identify ~8
luminous z-dropouts and possibly ~2 z~10 J-dropouts as a result of
this program, more than tripling the number currently known. The
increased sample sizes are important if we are to solidify current
conclusions about galaxy buildup and the evolution of the LF from z~8.
In addition to the high redshift science, these deep 1.1 micron data
would have significant value for many diverse endeavors, including {1}
improving our constraints on the stellar mass density at z~7-10 and
{2} doubling the number of galaxies at z~6 for which we can estimate
dust obscuration.

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************** 06**************** 06
FGS REacq************** 08**************** 08
OBAD with Maneuver **** 28**************** 28

SIGNIFICANT EVENTS: (None)