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 2.7<z<3.3 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, z>3.1 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 i
mages.
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 M>1e10 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 z>1
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)