This Echo is READ ONLY !   NO Un-Authorized Messages Please!
 ~~~~~~~~~~~~~~~~~~~~~~~~   ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

12 May 2003

HUBBLE SPACE TELESCOPE

DAILY REPORT        # 3360

PERIOD COVERED: DOYs 129-131

Part 2 of 5

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 9454

The Nature of the UV Continuum in LINERs: A Variability Test

LINERs may be the most common AGNs, and the signposts of accretion
onto the massive black holes present in most galaxies. However, the
LINER spectrum is the result of UV excitation, and, in at least some
LINERs, a nuclear cluster of hot stars, rather than an AGN, dominates
the energetics in the UV. Thus, it is still unknown if the UV
continuum, or the optical emission lines it excites, have anything to
do with an AGN. The demographics and accretion physics of
low-luminosity AGNs hinge on this question. We propose to search for
variability in a sample of 17 LINERs with compact UV nuclei.
Variability can reveal an AGN component in the UV continuum, even
when its light is not dominant. We will test systematically the
handful of non-definitive reports of UV variability, and potentially
quantify the AGN contribution to the UV emission. Variability in all
or most objects will be strong evidence that LINERs mark dormant AGNs
in most galaxies. Alternatively, a general null detection of
variability will suggest that, even in LINERs with additional AGN
signatures, the UV continuum is stellar in origin. Contemporaneous
monitoring with the VLA/VLBA of 11 objects which have radio cores
{five of which we already know are radio-variable} will reveal the
relations between UV and radio variations. The UV-variable objects
will be targeted for future, better-sampled, monitoring. 

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.

ACS/WFC 9351

Determining Hubble's Constant from Observations of Cepheids in the
Host Galaxy of SN Ia 1994ae

We propose to determine the luminosity of the type Ia supernova {SN
Ia} 1994ae by observing Cepheids in the host spiral galaxy NGC 3370.
Modern CCD photometry has yielded an extremely tight Hubble diagram
for SNe Ia with a precisely determined intercept {i.e., Delta
H_0/H_0} 1 measurement of the true Hubble constant is still limited
by the calibration. The HST calibration of all but a few SNe Ia
observed to date is significantly compromised by the systematics of
photographic photometry and host galaxy extinction, as well as by
the photometric uncertainties associated with WFPC2. In contrast, SN
1994ae is one of the very best-observed SNe Ia with CCD photometry.
The exquisite B, V, R, and I light curves are well-sampled beginning
10 days before maximum brightness, and they indicate little
reddening. From our supernova photometry and the current provisional
SN Ia calibration we would find a distance of 30 +/- 2.1 Mpc, well
within the range where ACS can accurately observe Cepheid light
curves and distinguish Cepheids from nonvariable stars. 

ACS/WFC/HRC 9445

Gravitational Microlensing in the NGC 3314A-B Galaxy Pair.

The Advanced Camera for Surveys (WFC and HRC) was used to determine
the composition of the dark matter that dominates the masses of
galaxies which is an important unsolved problem.

FGS 9329

The Masses and Luminosities of Population II Stars

Very little is currently known concerning the mass-luminosity
relation {MLR} of Population II stars. However, with the advent of
the Hipparcos Catalogue, improved distances to many spectroscopic
binaries known to be Pop II systems are now available. After
surveying the literature and making reasonable estimates of the
secondary masses, we find 13 systems whose minimum separation should
be larger than the resolution limit of FGS1. Because of the expected
magnitude differences and separations, it is not possible to resolve
the systems from the ground. We therefore propose FGS observations of
the sample. In combination with the known spectroscopic orbits and
Hipparcos distances, these observations will yield up to 26 precise
stellar mass determinations of metal-poor stars, if all systems are
resolved and the relative orbits are determined. A combination of FGS
data and ground-based observations will lead to component
luminosities and effective temperatures. This program will allow for
a significantly better understanding of the Pop II main sequence,
which in turn will lead to better ages and distances of the galactic
globular clusters, and a Pop II MLR will be constructed for the first
time. 
 - Continued -

@Message posted automagically by IMTHINGS POST 1.30
---