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28 April 2003

HUBBLE SPACE TELESCOPE

DAILY REPORT #3350

PERIOD COVERED: DOY 115-117

Part 1 of 5

OBSERVATIONS SCHEDULED


ACS 9658

ACS Earth Flats

This program will obtain sequences of flat field images by observing
the bright Earth. Several UV filters from the interim calibration
program {9564} require additional exposures to obtain the required
illumination. A few UV filters from this program will be repeated to
monitor for changes in the flat fields and to verify the interim
results. Since no streaks are observed in the UV, the wavelength
coverage is extended to longer wavelengths in order to explore the
severity of streaks in the flats from clouds in the FOV. We have
added exposures for the HRC in the visible filters to verify the
results derived from the L-flat campaign and to explore the severity
of streaks. We have also added exposures on WFC using the minimum
exposure time and using filters which will not saturate the brightest
WFC pixel by more than 10 times the full well. 

ACS 9468

ACS Grism Parallel Survey of Emission- line Galaxies at Redshift
z pl 7

We propose an ACS grism parallel survey to search for emission-line
galaxies toward 50 random lines of sight over the redshift interval
0 < zpl 7. We request ACS parallel observations of duration more than
one orbit at high galactic latitude to identify ~ 300 HAlpha
emission-line galaxies at 0.2pl zpl 0.5, ~ 720 O IILambda3727
emission-line galaxies at 0.3pl zpl 1.68, and pg 1000 Ly-alpha
emission-line galaxies at 3pl zpl 7 with total emission line flux
fpg 2* 10^-17 ergs s^-1 cm^-2 over 578 arcmin^2. We will obtain
direct images with the F814W and F606W filters and dispersed images
with the WFC/G800L grism at each position. The direct images will
serve to provide a zeroth order model both for wavelength calibration
of the extracted 1D spectra and for determining extraction apertures
of the corresponding dispersed images. The primary scientific
objectives are as follows: {1} We will establish a uniform sample of
HAlpha and O II emission-line galaxies at z<1.7 in order to obtain
accurate measurements of co-moving star formation rate density versus
redshift over this redshift range. {2} We will study the spatial and
statistical distribution of star formation rate intensity in
individual galaxies using the spatially resolved emission-line
morphology in the grism images. And {3} we will study high-redshift
universe using Ly-alpha emitting galaxies identified at z pl 7 in the
survey. The data will be available to the community immediately as
they are obtained.

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.

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.

ACS 9650

CCD Hot Pixel Annealing

Hot pixel annealing will be performed once every 4 weeks. The CCD
TECs will be turned off and heaters will be activated to bring the
WFC detector temperature to about +10C. The HRC temperature will
reach about 30C.This state will be held for approximately 24 hours,
after which the heaters are turned off, the TECs turned on, and the
CCDs returned to normal operating condition. To assess the
effectiveness of  this procedure, a bias and two dark images will be
taken before and after the annealing procedure for both WFC and HRC.

ACS 9480

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.

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