NASA Hubble Space Telescope Daily Report # 3406
DAILY REPORT # 3406
PERIOD COVERED: DOY 197
OBSERVATIONS SCHEDULED
ACS 9401
The ACS Virgo Cluster Survey
We propose the most comprehensive imaging survey to date of low-redshift,
early-type galaxies. Our goal is to exploit the exceptional imaging
capabilities
of the ACS by acquiring deep images — in the SDSS g^ and z^ bandpasses
— for
163 E, S0, dE, dE, N and dS0 galaxies in Virgo, the nearest rich cluster.
This
extraordinary dataset would likely constitute one of the principal legacies
of
HST, and would have widespread applications for many diverse areas of
astrophysics. Our immediate scientific objectives are threefold: {1} measure
metallicities, ages and radii for the many thousands of globular clusters
{GCs}
in these galaxies, and use this information to derive the protogalactic mass
spectrum of each galaxy; {2} measure the central luminosity and color
profile of
each galaxy, and use this information to carry out a completely independent
test
of the merging hierarchy inferred from the GCs, with the aid of N-body codes
that simulate the merger of galaxies containing massive black holes; and {3}
calibrate the z^ -band SBF method, measure Virgo’s 3-D structure, and carry
out
the definitive study of the GC luminosity function’s precision as a standard
candle. Our proposed Virgo Cluster Survey will yield a database of
unprecedented
depth, precision and uniformity, and will enable us to study the record of
galaxy and cluster formation in a level of detail which will never be
possible
with more distant systems.
STIS 9417
New Clues to the Origin of the Extreme Helium Stars
The extreme helium stars {EHes} are H-poor supergiants whose origins are
not yet
understood despite thorough analyses of optical spectra. This proposal seeks
STIS echelle spectra for 7 stars from which novel data on their chemical
compositions will be obtained to pin down key abundances. First, even the
EHe’s
initial metallicity is uncertain; certain abundance ratios – e.g., Ca/S,
Ti/S,
and Fe/S – imply alterations of surface abundances among elements from Na to
Ni
resulting from fractionation or diffusive separation, possibly the result of
winnowing of dust grains from gas. The zinc abundance measurable only from
UV
spectra will be a powerful clue to the true metallicity because it is known
not
to be removed by such winnowing. Second, elements affected by the
s-process, the
last of the major nucleosynthetic processes for which surface abundances are
unknown for EHes, will be studied. The new abundances will be used to probe
the
evolutionary origins of these peculiar stars by comparisons with theoretical
scenarios involving a merger of white dwarfs or a final He-shell flash in a
low
mass white dwarf, and with observed abundances for R Coronae Borealis stars
that
would seem to be close relatives of the EHes. Spectrophotometric
observations of
EHes obtained with GO 8603 will give accurate estimates of effective
temperature
and surface gravity that will be used in our abundance determinations.
ACS 9482
ACS Pure Parallel Lyman-Alpha Emission Survey {APPLES}
Ly-alpha line emission is an efficient tool for identifying young galaxies
at
high redshift, because it is strong in galaxies with young stars and little
or
no dust — properties expected in galaxies undergoing their first burst of
star- formation. Slitless spectroscopy with the ACS Wide-Field Camera and
G800L
grism allows an unmatched search efficiency for such objects over the
uninterrupted range 4 <~ z <~ 7. We propose the ACS Pure Parallel Ly-alpha
Emission Survey {“APPLES”}, to exploit this unique HST capability and so
obtain the largest and most uniform sample of high redshift Ly-alpha
emitters
yet. Parallel observations will allow this survey to be conducted with
minimal
impact on HST resources, and we will place reduced images and extracted
spectra
in the public domain within three months of observation. We aim to find ~
1000
Ly-alpha emitters, 5 times the biggest current sample of Ly-alpha emitters.
This
unprecedented sample will provide robust statistics on the populations and
evolution of Ly-alpha emitters between redshifts 4–7; a robust measurement
of
the reionization redshift completely independent of the Gunn-Peterson
trough;
spatial clustering information for Ly-alpha emitters which would let us
probe
their bias function and hence halo mass as a function of redshift; many
galaxies
at redshift exceeding 6; and lower redshift serendipitous discoveries.
STIS/CCD/MA2 9491
The Oxygen Abundance in the Metal-Poor Halo Star HD 140283 from UV-OH lines
Oxygen is critical in numerous astrophysical contexts, including the
derivation
of globular cluster ages and the early history of the Galaxy’s chemistry.
However, its abundance, particularly in metal-poor stars, remains
controversial,
with optical, IR and UV abundance indicators in dwarfs and giants yielding
different abundance patterns; a flat O/Fe ratio with Fe/H is suggested by
OI and
IR-OH lines, while a monotonically increasing O/Fe trend with decreasing
Fe/H is
measured from OI and UV-OH lines with a factor of 10 difference at Fe/H=-3.
We
propose an in-depth study of the UV- OH lines in the halo subgiant HD 140283
with R=110, 000 and S/N=200 spectra and state-of-the-art 3-D model
atmospheres.
Understanding UV-OH lines is particularly important because these provide
the
sole means of measuring the oxygen abundance in the most metal-poor stars
and
therefore in the early Galaxy. STIS will for the first time provide several
dozen unblended UV-OH lines. Predictions about the variation of line
strength
with excitation potential and the asymmetries of the OH line profiles will
be
tested and used to refine the cool outer layers of the 3-D models where the
OH
lines are formed. The end result will be an accurate oxygen abundance, a
thorough understanding of OH line formation, and a good characterization of
the
atmosphere of a metal-poor star.
WFPC2 9595
WFPC2 CYCLE 11 SUPPLEMENTAL DARKS pt3/3
This dark calibration program obtains 3 dark frames every day to provide
data
for monitoring and characterizing the evolution of hot pixels.
STIS 9606
CCD Dark Monitor-Part 2
Monitor the darks for the STIS CCD.
STIS 9608
CCD Bias Monitor – Part 2
Monitor the bias in the 1×1, 1×2, 2×1, and 2×2 bin settings at gain=1, and
1×1
at gain = 4, to build up high-S/N superbiases and track the evolution of hot
columns.
ACS 9674
CCD Daily Monitor
This program consists of basic tests to monitor, the read noise, the
development
of hot pixels and test for any source of noise in ACS CCD detectors. This
programme will be executed once a day for the entire lifetime of ACS.
STIS 9786
The Next Generation Spectral Library
We propose to continue the Cycle 10 snapshot program to produce a Next
Generation Spectral Library of 600 stars for use in modeling the integrated
light of galaxies and clusters. This program is using the low dispersion UV
and
optical gratings of STIS. The library will be roughly equally divided among
four
metallicities, very low {[Fe/H] lt -1.5}, low {[Fe/H] -1.5 to -0.5},
near-solar
{[Fe/H] -0.3 to 0.1}, and super-solar {[Fe/H] gt 0.2}, well-sampling the
entire
HR-diagram in each bin. Such a library will surpass all extant compilations
and
have lasting archival value, well into the Next Generation Space Telescope
era.
Because of the universal utility and community-broad nature of this venture,
we
waive the entire proprietary period.
NIC2 9801
Are OH/IR Stars the Youngest post-AGB stars? A NICMOS Imaging Survey
Essentially all well-characterized preplanetary nebulae {PPNe}– objects in
transition between the AGB and planetary nebula evolutionary phases – are
bipolar, whereas the mass-loss envelopes of AGB stars are strikingly
spherical.
In order to understand the processes leading to bipolar mass-ejection, we
need
to know at what stage of stellar evolution does bipolarity in the mass-loss
first manifest itself. We have recently hypothesized that most OH/IR stars
{evolved mass- losing stars with OH maser emission} are very young PPNe. We
are
conducting a multiwavelength survey program of imaging and spectroscopic
observations of such objects, using a large, morphologically unbiased sample
selected using IRAS 12-to-25 micron colors. Our ongoing HST/SNAP imaging
survey
of the optically bright half of this sample with WFPC2 and ACS is highly
successful: 19/32 objects observed are extended with bipolar/multipolar
shapes
{remaining objects are unresolved}. Slightly more than 50% of our sample are
optically too faint or undetected but have strong near-IR counterparts — we
therefore propose a NICMOS SNAPshot imaging survey of these optically-faint
OH/IR stars. These observations are crucial for determining how and when the
bipolar geometry asserts itself. The results from our NICMOS survey
{together
with the WFPC2/ACS survey} will allow us to draw general conclusions about
the
onset of bipolar mass-ejection during late stellar evolution. Our
complementary
program of interferometric mapping of the OH maser emission in our sources
is
yielding kinematic information with spatial resolution comparable to that
in the
HST images. The HST/radio data will provide crucial input for theories of
post-AGB stellar evolution. In addition, these data will also indicate
whether
the multiple concentric rings, "searchlight beams”, and truncated
equatorial
disks recently discovered with HST in a few PPNe, are common or rare
phenomena.
ACS/HRC/WFC 9815
The Bottom of the Main Sequence in the Old, Metal-Rich Cluster, NGC 6791
We propose a photometric study of the lowest part of the main sequence of
NGC
6791, an old, rich open cluster whose metallicity is considerably higher
than
solar. The cluster is rich enough that a single ACS/WFC field will have
ample
stars for the study. For the faintest stars, proper-motion separation of
cluster
from field is essential; hence we include Cycle 14 observations. These
should
give us a color-magnitude diagram and luminosity function that reach into
the
region of the hydrogen-burning limit, thus extending the study of the latter
into a new domain of metallicity. Observational data of this type will allow
theoreticians to check many aspects of their theories of stellar structure.
We
also expect to see the white dwarf sequence of the cluster. Our team has
experience with studies of this type, and has provided the
geometric-distortion
calibration of ACS.
ACS/WFC/HRC 9895
The Role of Groups in the Evolution of Galaxies at Intermediate Redshifts
Groups are the most common environment experienced by galaxies, yet they
remain
the least studied. The tidal fields and dynamical friction encountered by
galaxies in groups probably holds the key to understanding the role of
environment in driving the evolution of galaxies since z ~ 1. To study the
evolution of galaxies in the group environment, we propose the first
unbiased
HST study of groups at moderate redshifts. Unlike previous HST group
samples,
that relied on radio or X-ray properties, our kinematically selected sample
is
drawn from a large redshift survey and is not biased towards unusually dense
groups. HST imaging is essential to determine the morphology of galaxies in
these systems and contrast this with the properties of galaxies in denser
and
more evolved groups and rich clusters at these epochs. HST data are also
required to adequately compare the properties of groups at intermediate
redshifts with local group samples derived from the 2df and Sloan surveys.
We
will combine the HST images with deep ground-based observations to study how
morphologies and stellar populations of galaxies in groups have evolved in
time.
These observations are key to understanding the decline in the volume
averaged
star formation rate in the universe.
ACS 9984
Cosmic Shear With ACS Pure Parallels
Small distortions in the shapes of background galaxies by foreground mass
provide a powerful method of directly measuring the amount and distribution
of
dark matter. Several groups have recently detected this weak lensing by
large-scale structure, also called cosmic shear. The high resolution and
sensitivity of HST/ACS provide a unique opportunity to measure cosmic shear
accurately on small scales. Using 260 parallel orbits in Sloan textiti
{F775W}
we will measure for the first time: beginlistosetlength sep0cm
setlengthemsep0cm
setlength opsep0cm em the cosmic shear variance on scales <0.7 arcmin, em
the
skewness of the shear distribution, and em the magnification effect.
endlist Our
measurements will determine the amplitude of the mass power spectrum
sigma_8Omega_m^0.5, with signal-to-noise {s/n} ~ 20, and the mass density
Omega_m with s/n=4. They will be done at small angular scales where
non-linear
effects dominate the power spectrum, providing a test of the gravitational
instability paradigm for structure formation. Measurements on these scales
are
not possible from the ground, because of the systematic effects induced by
PSF
smearing from seeing. Having many independent lines of sight reduces the
uncertainty due to cosmic variance, making parallel observations ideal.
FLIGHT OPERATIONS SUMMARY:
Significant Spacecraft Anomalies: (The following are preliminary reports of
potential non-nominal performance that will be investigated.) None
COMPLETED OPS REQs: None
OPS NOTES EXECUTED:
1117-1 Battery 6 Capacity Test Limits (cancelled) @ 197/1827z
1135-0 Battery Pressure Ground Limits @ 197/2000z
SCHEDULED SUCCESSFUL FAILURE TIMES
FGS GSacq 7 7
FGS REacq 8 8
FHST Update 15 15
LOSS of LOCK
SIGNIFICANT EVENTS:
Successfully completed CCC Checkout testing 197/16:15Z -18:45Z. Icons for
the "D" and "F" strings have been added in the Packet Filter Management
window
under the Tools menu bar. All Packet Filters were checked during this test,
a
telemetry connection was made to each. Testing was conducted from the SMOR
using CCS "B" String and PRD O06100R1T.
