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27 Mar 2003

HUBBLE SPACE TELESCOPE

DAILY REPORT        # 3328

PERIOD COVERED: DOY 85

Part 1 of 2

OBSERVATIONS SCHEDULED

FLIGHT OPERATIONS SUMMARY:

ACS/HRC 9295

Coronagraphic search for disks around nearby stars

HD 163296 is a Herbig Ae star with a circumstellar disk that was
previously imaged using STIS. It is the source of a bipolar jet that
consists of discrete knots, also seen in the STIS images. HD 100546
is a Herbig Be star with a circumstellar disk that was previously
imaged using STIS and NICMOS. The STIS images show disk-like
circumstellar material with a somewhat spiral structure. GG Tauri is
a young binary {0.25" separation} that is surrounded by a
circumbinary disk that appears as an inclined ring with a semi-minor
axis of 1" and a semi-major axis of 1.8". The interior of the disk
has been cleared by tidal forces due to the binary, resulting in the
ring-like appearance. A gap in the ring is seen in HST and
ground-based adaptive optics images. It is likely a shadow cast by
material between the ring and the stars. WFPC2 images have revealed
material within 0.3" of the secondary star that might be dust trapped
at a Lagrangian point {it is too large to be a circumstellar disk}.
Verification  of this material is important as it may influence the
illumination of the outer ring. The WFPC2 images failed to detect the
far side of the ring in F555W due to the intrinsic faintness of the
ring at that wavelength {due to increased forward scattering} and PSF
subtraction residuals. The greater sensitivity of the ACS and its
more stable PSF should provide a definite detection of the far side,
providing important constraints on the relationship between
wavelength and the scattering phase, as well as possible reddening of
the ring caused by intervening dust. 

SNAP/STIS 9434

A SNAPSHOT Survey of the Hot Interstellar Medium

We propose to obtain SNAPSHOT STIS echelle observations of key
tracers of hot interstellar gas {CIV, NV and SiIV} for selected FUSE
Team OVI survey targets with known UV fluxes. By taking advantage of
the SNAPSHOT observing mode we will efficiently obtain a large number
of spectra suitable for the study of the highly ionized hot component
of the interstellar medium {ISM}. Our goals are to explore the
physical conditions in and distribution of such gas, as well as to
explore the nature of the interfaces between the hot ISM and the
other interstellar gas phases. Using inter--comparisons of the
various ionic ratios for CIV, NV, OVI and SiIV, we will be able to
discriminate between the various models for the production of the
highly ionized gas in the Galactic ISM. The survey will also enable
detailed studies of regions already known to contain hot gas through
X-ray emission measurements {e.g., SNRs and radio loops}. The
proposed SNAPSHOT observations will extend our previous Cycle 9
survey {which was compromised by the STIS side 1 failure}, and should
roughly double the number of stars for which high quality STIS
observations of the important hot gas tracers are available, enabling
us to derive a truly global view of the hot ISM.

ACS 9476

Galaxy Evolution in the Richest Clusters at z=0.8: the EDisCS Cluster
Sample

The study of distant cluster galaxies requires two key ingredients:
{1} deep high-resolution imaging, to constrain galaxy structure; and
{2} 8m-class spectroscopy, to measure stellar content, star-formation
rates, dynamics, and cluster membership. We will reach both
conditions with the addition of HST/ACS imaging to our suite of VLT
{36 nights} and NTT {20 nights} observations of 10 confirmed clusters
at z~0.8, drawn from the ESO Distant Cluster Survey {EDisCS}.

The proposed HST/ACS data will complement our existing optical/IR
imaging and spectroscopy with quantitative measures of cluster galaxy
morphologies {i.e. sizes and shapes, bulge-disk decompositions,
asymmetry parameters}, and with measurements of cluster masses via
weak lensing. Major advantages unique to the EDisCS project include:
{i} uniform selection of clusters; {ii} large enough sample sizes to
characterize the substantial cluster-to-cluster variation in galaxy
populations; {iii} large quantities of high quality data from 8m
telescopes; {iv} uniform measurements of morphologies, spectroscopic
and photometric redshifts, SEDs, star-formation/AGN activities, and
internal kinematics; {v} optical selection of clusters to complement
the X-ray selection of almost all high-z clusters in the ACS GTO
programs; {vi} forefront numerical simulations designed specifically
to allow physical interpretation of observed differences between the
high-z and local clusters. 

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. 

WFPC2 9594

WFPC2 CYCLE 11 SUPPLEMENTAL DARKS pt2/3

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.

 - Continued -

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