Status Report

NASA Hubble Space Telescope Daily Report # 3512

By SpaceRef Editor
December 19, 2003
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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
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.


The Ultra Deep Field with ACS

The ACS Ultra Deep Field {UDF} is a survey carried out by using Director’s
Discretionary time. The main science driver are galaxy evolution and cosmology.
The primary instrument is the Advanced Camera for Surveys but WFPC2 and NICMOS
will also be used in parallel. The data will be made public. The UDF
consists of
a single ultra-deep field {410 orbits in total} within the CDF-S GOODS
area. The
survey will use four filters: F435W {55 orbits}, F606W {55 orbits}, F775W {150
orbits}, and F850LP {150 orbits}. The F435W {B} and F606W {V} exposures will be
one magnitude deeper than the equivalent HDF filters. The F775W {I} exposure
will be 1.5 magnitude deeper than the equivalent HDF exposure. The depth in
F775W and F850LP is optimized for searching very red objects – like z=6
– at the detection limit of the F850LP image. The pointing will be RA{J2000}=3
32 40.0 and Decl.{J2000}=-27 48 00. These coordinates may change slightly
due to
guide star availability and implementation issues. We will attempt to
include in
the field both a spectroscopically confirmed z=5.8 galaxy and a
spectroscopically confirmed type Ia SN at z=1.3. The pointing avoids the gaps
with the lowest effective exposure on the Chandra ACIS image of CDFS. This
structure of the survey represents a consensus recommendation of a Scientific
Advisory Committee to the STScI Director Steven Beckwith. A local Working Group
is looking in detail at the implementation of the survey.


CCD Daily Monitor

This program consists of basic tests to monitor, the read noise, the
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/WFC 9744

HST Imaging of Gravitational Lenses

Gravitational lenses offer unique opportunities to study cosmology, dark
galactic structure, galaxy evolution and quasar host galaxies. They are
also the
only sample of galaxies selected based on their mass rather than their
luminosity or surface brightness. While gravitational lenses can be discovered
with ground-based optical and radio observations, converting them into
astrophysical tools requires HST. HST has demonstrated that it is the only
telescope that can in each case precisely locate the lens galaxy, measure its
luminosity, color and structure, and search for lensed images of the source
galaxy given the typical image separations of ~1”. We will obtain ACS/WFC
V and
I images and NICMOS H images of 21 new lenses never observed by HST and
images of 16 lenses never observed by HST in the IR. As in previous cycles, we
request that the data be made public immediately.


Accurate and Robust Calibration of the Extragalactic Distance Scale with the
Maser Galaxy NGC4258

The extragalactic distance scale {EDS} is defined by a comparison of Cepheid
Period-Luminosity {PL} relations for nearby galaxies and the LMC, whose
uncertain distance is thereby the SOLE anchor. Studies of maser sources
the central black hole in the galaxy NGC4258 have provided the most accurate
extragalactic distance ever {7.2+/- 0.5Mpc}. Since this distance is well
determined and based on GEOMETRIC arguments, NGC4258 can provide a much needed
new anchor for the EDS. We propose multi-epoch BVIH observations of NGC4258 in
order to discover about 100 Cepheids and to characterize their light curves
2-3 times greater accuracy than was previously possible with WFPC2. At 90
{48 in Cycle 12; 42 in Cycle 13}, this is a relatively large program. However,
the result will have a major impact on the EDS, and substantial attention must
be paid to characterization and minimization of systematic errors, as from
metallicity, crowding, and blending. The resulting dataset will be the most
complete for Cepheids in any galaxy yet studied with HST. In an ongoing
NASA-funded program {OSS-SARA}, we are using new analysis techniques and radio
data to reduce uncertainty in the geometric distance to < 3% {0.07 mag}. With this improved geometric distance and the BVIH data, we will be able to calculate the zero point of the PL relation ROBUSTLY to <4% {0.09 mag}.

NIC/NIC3 9865

The NICMOS Parallel Observing Program

We propose to continue managing the NICMOS pure parallel program. Based on our
experience, we are well prepared to make optimal use of the parallel
opportunities. The improved sensitivity and efficiency of our observations will
substantially increase the number of line-emitting galaxies detected. As our
previous work has demonstrated, the most frequently detected line is Halpha at

NIC3 9979

The Ultra Deep Field – NICMOS Parallels

This is a plan to manage the NICMOS pure parallels of the ACS Ultra Deep
We will obtain a mix of F110W and F160W images along sight-lines within the
mosaiced ACS fields of the CDF-S GOODS and GEMS surveys, with these sight-lines
enabling an examination of the space density and morphologies of the reddest


NICMOS Post-SAA calibration – CR Persistence Part 1.

A new procedure proposed to alleviate the CR-persistence problem of NICMOS.
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
darks will be non-standard reference files available to users with a USEAFTER
date/time mark.

S/C 4974


No available description

STIS/CCD 10000

STIS Pure Parallel Imaging Program: Cycle 12

This is the default archival pure parallel program for STIS during cycle 12.

STIS/CCD 10017

CCD Dark Monitor-Part 1

Monitor the darks for the STIS CCD.

STIS/CCD 10019

CCD Bias Monitor – Part 1

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


The Ultra Deep Field – STIS parallels

We propose to obtain slitless spectroscopy of objects in the GEMS and GOODS
around the UDF.

STIS/MA1 10034

Cycle 12 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

WFPC2 10069

WFPC2 CYCLE 12 Supplemental Darks, Part 1/3

This dark calibration program obtains 3 dark frames every day to provide data
for monitoring and characterizing the evolution of hot pixels.

WFPC2 9980

The Ultra Deep Field – WFPC2 Parallels

The ACS Ultra Deep Field {UDF} is a survey carried out by using Director’s
Discretionary time. The main science drivers are galaxy evolution and
The primary instrument is the Advanced Camera for Surveys but WFPC2,
STIS will also be used in pure parallel mode. The data will be made public. The
UDF consists of a single ultra-deep field {410 orbits in total} within the
GOODS area. We request a modification of the default pure parallel programs.
Rather than duplicate the redder bands which will be done much better with ACS,
we propose to observe in the near-ultraviolet F300W filter. These data will
enable study of the rest-frame ultraviolet morphology of galaxies at 0


Significant Spacecraft Anomalies: (The following are preliminary reports of
potential non-nominal performance that will be investigated.) None



                         SCHEDULED     SUCCESSFUL    FAILURE TIMES
FGS GSacq             08                        08
FGS REacq             07                        07
FHST Update           06                        06


SpaceRef staff editor.