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Daily 3410



 
 
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Old July 23rd 03, 02:55 PM
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Default Daily 3410


HUBBLE SPACE TELESCOPE

DAILY REPORT******* # 3410

PERIOD COVERED: DOY 203

OBSERVATIONS SCHEDULED

ACS/HRC 9361

Searching for Primeval Galaxies: the promising case of SBS 1415+437

Do primeval galaxies exist in the local Universe? The best candidates
are extremely metal-poor {Z 1/20 Zo} blue compact dwarf {BCD}
galaxies whose photometric and chemical properties are consistent with
a stellar population younger than 100 Myr. SBS 1415+437 {Z = 1/21 Zo}
is the closest candidate: its proximity {d = 11.4 Mpc}, detailed
spectroscopic knowledge of its HII regions and low metal content, used
to infer the primordial He^4 abundance, make it the best target for
this investigation. We propose to take deep exposures of SBS 1415+437
with the ACS in the F814W and F606W filters. This instrument has
resolution and magnitude limits allowing us to reach and resolve with
the required accuracy individual stars 1 mag below the tip of the red
giant branch {RGBT}. If present, these stars will provide a clear sign
of an old stellar population {with ages 1 Gyr} and an independent
distance indicator. If absent, this will unambiguously show that the
system has started to form stars only recently and can be considered
the first robust case of local primeval galaxy. We propose to take
exposures in the F658N {HAlpha Lambda6563} and FR505N {HBeta
Lambda4861} filters to study the morphology of the ionized gas through
HAlpha emission and map the dust content with the HAlpha/HBeta ratio
in order to solve the age-dust degeneracy of the photometry by
constraining reddening effects.

HST 9382

A Large Targeted Survey for z 1.6 Damped Lyman Alpha Lines in SDSS QSO
MgII-FeII Systems.

We have searched the first public release of SDSS QSO spectra for
low-z {z1.65} metal absorption lines and found over 200 large rest
equivalent width MgII-FeII systems. Previously, we empirically showed
that such systems are good tracers of large neutral gas columns, with
~50% being classical damped Lyman alpha {DLA} systems {N_HI=2*10^20
cm^-2}. Here we propose to follow up a well-defined subset of 79 of
them to search for DLAs with 0.47z1.60. Only QSOs brighter than
g'=19 were selected. The QSO emission and DLA absorption redshifts
were constrained to virtually eliminate data loss due to intervening
Lyman limit absorption. Consequently, we expect to discover ~40 new
DLAs, which is a three-fold increase in this redshift interval. This
will significantly improve our earlier low-z DLA statistical results
on their incidence, cosmological mass density, and N_HI distribution.
The results will also allow us to better quantify the empirical DLA --
metal-line correlation. With this improved understanding, the need for
follow-up UV spectroscopy will lessen and, with the release of the
final database of SDSS QSO spectra {an ~25-fold increase}, the number
of low-z DLAs could be increased arbitrarily. Thus, the power of the
large and statistically-sound SDSS database in combination with a
proven technique for finding low-z DLAs will, over the next few years,
essentially solve the problem of making an accurate determination of
the cosmic evolution of the neutral gas component down to z~0.4.

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 1x1, 1x2, 2x1, and 2x2 bin settings at gain=1,
and 1x1 at gain = 4, to build up high-S/N superbiases and track the
evolution of hot columns.

STIS 9615

Cycle 11 MAMA Dark Monitor

This test performs the routine monitoring of the MAMA detector dark
noise. This proposal will provide the primary means of checking on
health of the MAMA detectors systems through frequent monitoring of
the background count rate. The purpose is to look for evidence of
change in dark indicative of detector problem developing.

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 9708

STIS Pure Parallel Imaging Program: Cycle 11

This is the default archival pure parallel program for STIS during cycle
11.

WFPC2 9709

POMS Test Proposal: WFII parallel archive proposal

This is the generic target version of the WFPC2 Archival Pure Parallel
program. The program will be used to take parallel images of random
areas of the sky, following the recommendations of the 2002 Parallels
Working Group.

WFPC2 9710

POMS Test Proposal: WFII backup parallel archive proposal

This is a POMS test proposal designed to simulate scientific plans.

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.

ACS/WFC/HRC 9889

ACS Photometric Zero Point Verification

The uncertainties in the photometric zero points create a fundamental
limit to the accuracy of photometry. The current state of the ACS
calibration is surprisingly poor, with zero point uncertainties of
0.03 magnitudes in the Johnson filters. The reason for this is that
ACS observations of excellent ground-based standard fields, such as
the omega Cen field used for WFPC2 calibrations, have not been
obtained. Instead, the ACS photometric calibrations are based
primarily on semi-emprical synthetic zero points and observations of
fields too crowded for accurate ground-based photometry. I propose to
remedy this problem by obtaining ACS broadband images of the omega Cen
standard field with both the WFC and HRC. This will permit the direct
determination of the ACS transformations, and is expected to double
the accuracy to which the ACS zero points are known. A second benefit
is that it will facilitate the comparison of the WFPC2 and ACS
photometric systems, which will be important as WFPC2 is phased out
and ACS becomes HST's primary imager

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.)

HSTAR 9094:* Upon AOS @ 203/10:44Z, HST was operating in FL backup on
FGS 3 only.* Further information after engineering recorder playback.
Under investigation.

COMPLETED OPS REQs: None

OPS NOTES EXECUTED: None

*************************** SCHEDULED**** SUCCESSFUL*** FAILURE TIMES
FGS GSacq*************** 9************************* 9
FGS REacq*************** 7************************* 7
FHST Update************* 15*********************** 15
LOSS of LOCK

SIGNIFICANT EVENTS:

Back-up Packet Filter 13 test scheduled 204/16:00Z - 20:00Z with GDOC,
SOC, HITT, CCS, Sys Admin using CCS "C" String with CCS Release 4.0.2,
PRD S07200, and Building 25 SOC CCSPSS with Release 3.2.8.2.* The
purpose of this test is to verify the functionality of back-up Packet
Filter 13 for Service Mission operations.*



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