NASA Hubble Space Telescope Daily Report # 3379 (part 1)

HUBBLE SPACE TELESCOPE

DAILY REPORT # 3379

PERIOD COVERED: DOYs 157-159

OBSERVATIONS SCHEDULED

ACS 9472

A Snapshot Survey for Gravitational Lenses among z >= 4.0 Quasars

Over the last few years, the Sloan Digital Sky Survey has revolutionized the
study of high-redshift quasars by discovering over 200 objects with redshift
greater than 4.0, more than doubling the number known in this redshift
interval.
The sample includes eight of the ten highest redshift quasars known. We
propose
a snapshot imaging survey of a well-defined sample of 250 z > 4.0 quasars in
order to find objects which are gravitationally lensed. Lensing models
including
magnification bias predict that at least 4% of quasars in a flux-limited
sample
at z > 4 will be multiply lensed. Therefore this survey should find of order
10
lensed quasars at high redshift; only one gravitationally lensed quasar is
currently known at z > 4. This survey will provide by far the best sample to
date of high-redshift gravitational lenses. The observed fraction of lenses
can
put strong constraints on cosmological models, in particular on the
cosmological
constant Lambda. In addition, magnification bias can significantly bias
estimates of the luminosity function of quasars and the evolution thereof;
this
work will constrain how important an effect this is, and thereby give us a
better understanding of the evolution of quasars and black holes at early
epochs, as well as constrain models for black hole formation.

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 9400

ARE THERE YOUNG GALAXIES IN THE LOCAL UNIVERSE: THE AGE OF THE BLUE COMPACT
DWARF GALAXY I ZW 18

The question of whether there exists young galaxies in the local universe is
important for cosmology. Cold Dark matter models predict that low-mass
galaxies
could still be forming at the present epoch. In the hierarchical model of
galaxy
formation, large galaxies result from the merging of smaller structures.
These
primordial building-block galaxies are too faint and small to be studied at
high
redshifts, while we stand a much better chance of understanding them if we
can
find some local examples. One of the best candidates for being a young
nearby
galaxy forming stars for the first time at the present epoch, is the blue
compact dwarf {BCD} galaxy I Zw 18 because of its extremely low heavy
element
content {2% that of the Sun}. We propose to obtain deep $V$ and $I$ ACS
images
of I Zw 18. Our goal is to detect or put limits on the red giant branch
{RGB}
stellar population in this galaxy. If RGB stars are not detected, then we
can
set an upper limit for the age of I Zw 18 to be less than 1 Gyr. If they are
detected, I Zw 18 is not young, and the RGB tip can be used to derive its
distance and set limits on the metallicity of the pregalactic gas.

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 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.

ACS 9714

Hubble Heritage Observations of the Sombrero Galaxy

The Hubble Heritage Team will observe the entire Sombrero Galaxy {M104, NGC
4594} with a 6-point ACS mosaic. A color composite image will be released
to the
public via the Heritage website and an STScI photo release.

ACS 9462

Systemic and Internal Proper Motions of the Magellanic Clouds from
Astrometry
with ACS

We request first epoch observations with ACS of Magellanic Cloud fields
centered
on background quasars. Second epoch observations will be requested ~ 5 years
later to allow the measurement of the systemic and internal proper motions
of
the Clouds with error <~0.05 mas/year. These motions are of fundamental
importance. The systemic motions of the LMC and SMC probe the gravitational
potential of the dark halo. The internal proper motion due to rotation can
be
exploited to yield a rotational parallax distance to the LMC; the first time
that this will be done for any galaxy. This is particularly important for
the
LMC because of its crucial role in the extragalctic distance ladder.
Previous
measurements of the proper motion of the LMC yield a systemic component
ranging
from 1.4 mas/year to 3.4 mas/year {differing by several times the quoted
errors}, with no useful determination of the internal motions. The main
problem
with measurements of the proper motion of the LMC has been the lack of a
sample
of background quasars to use as reference frame. We have recently been able
to
identify a sample of 54 quasars behind the Magellanic Clouds from their
variability characteristics in the MACHO database. With this sample and the
advent of ACS an accurate proper motion measurement has become possible for
the
very first time.

ACS 9401

The ACS Virgo Cluster Survey

We propose the most comprehensive imaging survey to date of low-redshift,
early-type galaxies. Our goal is to exploit the exceptional imaging
capabilities
of the ACS by acquiring deep images — in the SDSS g^ and z^ bandpasses
— for
163 E, S0, dE, dE, N and dS0 galaxies in Virgo, the nearest rich cluster.
This
extraordinary dataset would likely constitute one of the principal legacies
of
HST, and would have widespread applications for many diverse areas of
astrophysics. Our immediate scientific objectives are threefold: {1} measure
metallicities, ages and radii for the many thousands of globular clusters
{GCs}
in these galaxies, and use this information to derive the protogalactic mass
spectrum of each galaxy; {2} measure the central luminosity and color
profile of
each galaxy, and use this information to carry out a completely independent
test
of the merging hierarchy inferred from the GCs, with the aid of N-body codes
that simulate the merger of galaxies containing massive black holes; and {3}
calibrate the z^ -band SBF method, measure Virgo’s 3-D structure, and carry
out
the definitive study of the GC luminosity function’s precision as a standard
candle. Our proposed Virgo Cluster Survey will yield a database of
unprecedented
depth, precision and uniformity, and will enable us to study the record of
galaxy and cluster formation in a level of detail which will never be
possible
with more distant systems.

ACS/HRC 9391

High-Resolution Imaging of Pluto’s Surface

We will collect a series of observations with the ACS/HRC from which we will
derive a two-color global map of Pluto’s surface. We will image Pluto at
F435W
and F555W, wavelengths that have been extensively studied from the ground
over
the past 50 years. The maps will provide albedos with accurate error
determinations down to 52 degrees South latitude. These observations will
provide a second epoch of HST mapping of the active surface of Pluto as it
continues to recede from the Sun and will provide an important context for
other
detailed studies of Pluto.

ACS/HRC 9379

Near Ultraviolet Imaging of Seyfert Galaxies: Understanding the
Starburst-AGN
Connection

We propose a near-UV snapshot survey of 101 Seyfert galaxies using ACS/HRC
and
the filter F330W, a configuration which is optimal to detect faint star
forming
regions around their nuclei. These images will complement optical and
near-IR
images available in the HST archive, thus providing a panchromatic atlas of
the
inner regions of active galaxies, which we will use to study the
starburst-AGN
connection. The main goals of this proposal are: {1} Determine the frequency
of
circumnuclear starbursts in Seyferts, down to levels which cannot be
observed
from the ground; {2} characterize the observational {fluxes, colors,
structure,
sizes} and intrinsic {luminosities, masses, ages, global star-formation
rate}
properties of these clusters; {3} derive the luminosity functions of young
star
clusters around the nucleus of Seyferts and compare these results with those
from normal and starburst galaxies to determine their survival rate close
to the
AGN; {4} address questions about the relation between AGNs and starbursts,
like
the possible connection between the masses and luminosities of black holes
and
starbursts, and the implications for the evolution of the black holes and
their
host galaxy bulges. By adding UV images to the existing optical and near-IR
ones, this project will create an extremely valuable database for
astronomers
with a broad range of scientific interests, from the properties of the AGN
to
the properties of their host galaxies.

FGS 9348

The Distances to AM CVn stars

We propose to determine the parallaxes and proper motions of the five
brightest
of the seven known AM CVn systems using the HST Fine Guidance Sensors. AM
CVn
systems are binaries where mass is transferred from a completely
hydrogen-deficient, degenerate mass donor to a white dwarf primary through a
helium accretion disk. A better understanding of these systems is crucial
for a
number of reasons:, to study the late stages of binary evolution, to study
the
effect of chemical composition on the physics of accretion discs; , o to
estimate their contribution to the Supernovae Ia rate and , to estimate
their
contribution to the gravitational radiation background. All these studies
rely
critically on a determination of the distances to the currently known
systems.
With brightnesses in the range 13<V<17 and estimated distances <400pc they
are
ideal targets for the HST-FGS.

GTO/ACS 9291

Formation of High Redshift Radio Galaxies

This programme uses ACS observations of high redshift radio galaxies {HzRGs}
to
investigate massive galaxy and cluster formation in the early Universe. By
carrying out deep observations of a few z > 3.8 targets the following four
questions will be studied: {1} Are HzRGs massive central-cluster galaxies
formed
through hierarchical assembly of Lyman break galaxies? Detailed brightness
distributions colors and morphologies of HzRG clumps will be measured and
compared with those of Lyman break galaxies. {2} Are HzRGs located in dense
{proto-} clusters and if so what are the properties of the associated
large-scale structures? Lyman alpha excesses, colors and morphologies of
objects
in field will be used to search for companion galaxies of HzRGs. {3} What
are
the origin and fate of giant gas halos associated with HzRGs and what role
do
they play in the formation of massive galaxies? The morphologies and
locations
of Ly-alpha clumps will be compared with those of continuum clumps. {4} Is
nuclear activity a source of star formation in the early Universe? The
properties of continuum and Ly-alpha clumps along will be compared in
relation
to the radio jet.