Status Report

NASA Hubble Space Telescope Daily Report # 3507

By SpaceRef Editor
December 11, 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.


Young Massive Clusters in Spiral Galaxies and the Connection with Open

We propose to carry out a census of star clusters in the disks of the nearby
spiral galaxies NGC 45, NGC 1313, NGC 4395, NGC 5236 and NGC 7793. Using
ACS, we
will identify much fainter and older star clusters than possible in previous
ground-based surveys, or even in HST imaging of more distant galaxies. For the
first time, we will directly explore the connection between young
“massive” {or
“super”} star clusters {YMCs} and lower-mass “open” clusters in different
forming environments. We will test the universality of the luminosity- and mass
functions of stellar clusters and establish whether the presence of YMCs is a
result of a top-heavy cluster luminosity function, or follows from generally
richer cluster systems. Our target galaxies span a range of morphological
properties, surface brightness and star formation rate. Some of them are known
from ground-based studies to host large numbers of YMCs while others have more
modest cluster populations. However, previous ground-based data were restricted
to luminous clusters younger than about 500 Myr. Here we will extend the search
to clusters formed throughout the entire lifetime of each galaxy and reach
clusters with properties typical of the Milky Way open clusters. This will
us to close the gap between studies of extragalactic and Galactic disk


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

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

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.

STIS 9633

STIS parallel archive proposal – Nearby Galaxies – Imaging and Spectroscopy

Using parallel opportunities with STIS which were not allocated by the TAC, we
propose to obtain deep STIS imagery with both the Clear {50CCD} and Long-Pass
{F28X50LP} filters in order to make color-magnitude diagrams and luminosity
functions for nearby galaxies. For local group galaxies, we also include G750L
slitless spectroscopy to search for e.g., Carbon stars, late M giants and
stars. This survey will be useful to study the star formation histories,
chemical evolution, and distances to these galaxies. These data will be placed
immediately into the Hubble Data Archive.

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.

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 10075

WFPC2 CYCLE 12 Intflat and Viflat Sweeps and Filter Rotation Anomaly Monitor

Using intflat observations, this WFPC2 proposal is designed to monitor the
pixel-to-pixel flatfield response and provide a linearity check. The intflat
sequences, to be done once during the year, are similar to those from the Cycle
11 program 9597. The images will provide a backup database in the event of
complete failure of the visflat lamp as well as allow monitoring of the gain
ratios. The sweep is a complete set of internal flats, cycling through both
shutter blades and both gains. The linearity test consists of a series of
intflats in F555W, in each gain and each shutter. As in Cycle 11, we plan to
continue to take extra visflat, intflat, and earthflat exposures to test the
repeatability of filter wheel motions.

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


Age-dating Star Clusters in M101

M101 represents perhaps our best chance to study the stellar population of a
luminous, late type spiral galaxy, due to both its proximity and its face-on
orientation. For these reasons, 13 orbits of HST ACS observing time were
allocated in Cycle 11 to obtain a 4×4 mosaic image of M101 in BVI .
Unfortunately, a degeneracy between age and reddening exists when only these
three bands are available. Hence, we propose to augment these observations by
obtaining WFPC2 U band and ACS H alpha images. This will enable the accurate
determination of ages for the young clusters, secure identifications of 75-100
old globular clusters, and allow a quantitative study of the HII region sizes
and structures. Some of the specific questions we will address are: How do the
young clusters form and evolve? What fraction of the clusters dissolve and on
what timescales? Do clusters evolve with a continuum of properties? Using WFPC2
and ACS in parallel, and making use of the fact that M101 is in the CVZ, allows
us to greatly enhance the science return of previous HST observations for the
cost of only 4 orbits.


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



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


RMGA Calibration Test scheduled 345/16:40Z – 19:41Z (OR 17067 with attached
RMGA Cal Script).

CCS Release deploy to CCS “B” and “G” Strings and CCS Release to CCS “D”
and “F” Strings. See GSCA 732-1 for details.

HST Transient Rate OAT scheduled 345/11:00Z – 346/05:00Z with GDOC, HITT,
SE, and VEST
using CCS “C” String with CCS Release 4.0.3 and PRD O06300T. The purpose
of this testing
is to perform a functional test of the FGS-2R MACROs against the
brassboard, including
verifying FGS diagnostic data and to install and test the FGS-2R MACROs in
an operational

HST Command Timing test scheduled 345/12:00Z – 22:00Z with GDOC, SOC, HITT,
and CCS using
CCS “B” String with CCS Release and PRD O06300T. The purpose of
this testing is
to check the command timing for CCS Release with historical,
baselined numbers.

SpaceRef staff editor.