HUBBLE SPACE TELESCOPE - Continuing to collect World Class
Science
DAILY REPORT #4743
PERIOD COVERED: 5am November 21 - 5am November 24, 2008
(DOY
326/1000z-329/1000z)
OBSERVATIONS SCHEDULED
WFPC2 11289
SL2S: The Strong Lensing Legacy Survey
Recent systematic surveys of strong galaxy-galaxy lenses
{CLASS, SLACS,
GOODS, etc.} are producing spectacular results for galaxy
masses roughly
below a transition mass M~10^13 Mo. The observed lens properties
and
their evolution up to z~0.2, consistent with numerical
simulations, can
be described by isothermal elliptical potentials. In
contrast, modeling
of giant arcs in X-ray luminous clusters {halo masses M
>~10^13 Mo}
favors NFW mass profiles, suggesting that dark matter
halos are not
significantly affected by baryon cooling. Until recently,
lensing
surveys were neither deep nor extended enough to probe the
intermediate
mass density regime, which is fundamental for
understanding the assembly
of structures. The CFHT Legacy Survey now covers 125
square degrees, and
thus offers a large reservoir of strong lenses probing a
large range of
mass densities up to z~1. We have extracted a list of 150
strong lenses
using the most recent CFHTLS data release via automated
procedures.
Following our first SNAPSHOT proposal in cycle 15, we
propose to
continue the Hubble follow-up targeting a larger list of
130 lensing
candidates. These are intermediate mass range candidates
{between
galaxies and clusters} that are selected in the redshift
range of 0.2-1
with no a priori X-ray selection. The HST resolution is
necessary for
confirming the lensing candidates, accurate modeling of
the lenses, and
probing the total mass concentration in galaxy groups up
to z~1 with the
largest unbiased sample available to date.
WFPC2 11218
Snapshot Survey for Planetary Nebulae in Globular Clusters
of the Local
Group
Planetary nebulae {PNe} in globular clusters {GCs} raise a
number of
interesting issues related to stellar and galactic
evolution. The number
of PNe known in Milky Way GCs, 4, is surprisingly low if
one assumes
that all stars pass through a PN stage. However, it is
likely that the
remnants of stars now evolving in Galactic GCs leave the
AGB so slowly
that any ejected nebula dissipates long before the star
becomes hot
enough to ionize it. Thus there should not be ANY PNe in
Milky Way
GCs--but there are four! It has been suggested that these
PNe are the
result of mergers of binary stars within GCs, i.e., that
they are
descendants of blue stragglers. The frequency of
occurrence of PNe in
external galaxies poses more questions, because it shows a
range of
almost an order of magnitude. I propose a Snapshot survey
aimed at
discovering PNe in the GC systems of Local Group galaxies
more distant
than the Magellanic Clouds. These clusters, some of which
may be much
younger than their counterparts in the Milky Way, might
contain many
more PNe than those of our own galaxy. I will use the
standard technique
of emission-line and continuum imaging, which easily
discloses PNe.
FGS 11212
Filling the Period Gap for Massive Binaries
The current census of binaries among the massive O-type
stars is
seriously incomplete for systems in the period range from
years to
millennia because the radial velocity variations are too
small and the
angular separations too close for easy detection. Here we
propose to
discover binaries in this observational gap through a
Faint Guidance
Sensor SNAP survey of relatively bright targets listed in
the Galactic O
Star Catalog. Our primary goal is to determine the binary
frequency
among those in the cluster/association, field, and runaway
groups. The
results will help us assess the role of binaries in
massive star
formation and in the processes that lead to the ejection
of massive
stars from their natal clusters. The program will also
lead to the
identification of new, close binaries that will be targets
of long term
spectroscopic and high angular resolution observations to
determine
their masses and distances. The results will also be
important for the
interpretation of the spectra of suspected and newly
identified binary
and multiple systems.
WFPC2 11201
Systemic and Internal motions of the Magellanic Clouds:
Third Epoch
Images
In Cycles 11 and 13 we obtained two epochs of ACS/HRC data
for fields in
the Magellanic Clouds centered on background quasars. We
used these data
to determine the proper motions of the LMC and SMC to
better than 5% and
15% respectively. These are by far the best determinations
of the proper
motions of these two galaxies. The results have a number
of unexpected
implications for the Milky Way-LMC-SMC system. The implied
three-dimensional velocities are larger than previously
believed, and
are not much less than the escape velocity in a standard
10^12 solar
mass Milky Way dark halo. Orbit calculations suggest the
Clouds may not
be bound to the Milky Way or may just be on their first
passage, both of
which would be unexpected in view of traditional
interpretations of the
Magellanic Stream. Alternatively, the Milky Way dark halo
may be a
factor of two more massive than previously believed, which
would be
surprising in view of other observational constraints.
Also, the
relative velocity between the LMC and SMC is larger than
expected,
leaving open the possibility that the Clouds may not be
bound to each
other. To further verify and refine our results we now
request an epoch
of WFPC2/PC data for the fields centered on 40 quasars
that have at
least one epoch of ACS imaging. We request execution in
snapshot mode,
as in our previous programs, to ensure the most efficient
use of HST
resources. A third epoch of data of these fields will
provide crucial
information to verify that there are no residual systematic
effects in
our previous measurements. More importantly, it will
increase the time
baseline from 2 to 5 yrs and will increase the number of
fields with at
least two epochs of data. This will reduce our
uncertainties
correspondingly, so that we can better address whether the
Clouds are
indeed bound to each other and to the Milky Way. It will
also allow us
to constrain the internal motions of various populations
within the
Clouds, and will allow us to determine a distance to the
LMC using
rotational parallax.
WFPC2 11130
AGNs with Intermediate-mass Black Holes: Testing the Black
Hole-Bulge
Paradigm, Part II
The recent progress in the study of central black holes in
galactic
nuclei has led to a general consensus that supermassive
{10^6-10^9 solar
mass} black holes are closely connected with the formation
and
evolutionary history of large galaxies, especially their
bulge
component. Two outstanding issues, however, remain
unresolved. Can
central black holes form in the absence of a bulge? And
does the mass
function of central black holes extend below 10^6 solar
masses?
Intermediate-mass black holes {<10^6 solar masses}, if
they exist, may
offer important clues to the nature of the seeds of
supermassive black
holes. Using the SDSS, our group has successfully
uncovered a new
population of AGNs with intermediate-mass black holes that
reside in
low-luminosity galaxies. However, very little is known
about the
detailed morphologies or structural parameters of the host
galaxies
themselves, including the crucial question of whether they
have bulges
or not. Surprisingly, the majority of the targets of our
Cycle 14 pilot
program have structural properties similar to dwarf
elliptical galaxies.
The statistics from this initial study, however, are
really too sparse
to reach definitive conclusions on this important new
class of black
holes. We wish to extend this study to a larger sample, by
using the
Snapshot mode to obtain WFPC2 F814W images from a parent
sample of 175
AGNs with intermediate- mass black holes selected from our
final SDSS
search. We are particularly keen to determine whether the
hosts contain
bulges, and if so, how the fundamental plane properties of
the host
depend on the mass of their central black holes. We will
also
investigate the environment of this unique class of AGNs.
WFPC2 11113
Binaries in the Kuiper Belt: Probes of Solar System
Formation and
Evolution
The discovery of binaries in the Kuiper Belt and related
small body
populations is powering a revolutionary step forward in
the study of
this remote region. Three quarters of the known binaries
in the Kuiper
Belt have been discovered with HST, most by our snapshot
surveys. The
statistics derived from this work are beginning to yield
surprising and
unexpected results. We have found a strong concentration
of binaries
among low-inclination Classicals, a possible size cutoff
to binaries
among the Centaurs, an apparent preference for nearly
equal mass
binaries, and a strong increase in the number of binaries
at small
separations. We propose to continue this successful
program in Cycle 16;
we expect to discover at least 13 new binary systems,
targeted to
subgroups where these discoveries can have the greatest
impact.
WFPC2 11103
A Snapshot Survey of The Most Massive Clusters of Galaxies
We propose the continuation of our highly successful
SNAPshot survey of
a sample of 125 very X-ray luminous clusters in the
redshift range
0.3-0.7. As demonstrated by the 25 snapshots obtained so
far in Cycle14
and Cycle15 these systems frequently exhibit strong
gravitational
lensing as well as spectacular examples of violent galaxy
interactions.
The proposed observations will provide important
constraints on the
cluster mass distributions, the physical nature of galaxy-galaxy
and
galaxy-gas interactions in cluster cores, and a set of
optically bright,
lensed galaxies for further 8-10m spectroscopy. All of our
primary
science goals require only the detection and
characterization of
high-surface-brightness features and are thus achievable
even at the
reduced sensitivity of WFPC2. Because of their high
redshift and thus
compact angular scale our target clusters are less
adversely affected by
the smaller field of view of WFPC2 than more nearby
systems.
Acknowledging the broad community interest in this sample
we waive our
data rights for these observations. Due to a clerical
error at STScI our
approved Cycle15 SNAP program was barred from execution
for 3 months and
only 6 observations have been performed to date - reinstating
this SNAP
at Cycle16 priority is of paramount importance to reach
meaningful
statistics.
WFPC2 10880
The Host Galaxies of QSO2s: AGN Feeding and Evolution at
High
Luminosities
Now that the presence of supermassive black holes in the
nuclei of
galaxies is a well established fact, other questions
related to the AGN
phenomena still have to be answered. Problems of
particular interest are
how the AGN gets fed, how the black hole evolves and how
the evolution
of the black hole is related to the evolution of the
galaxy bulge. Here
we propose to address some of these issues using ACS/WFC +
F775W
snapshot images of 73 QSO2s with redshifts in the range
0.3<z<0.4. These
observations will be combined with similar archival data
of QSO1s and
ground based data of Seyfert and normal galaxies. First,
we will
investigate whether interactions are the most important
feeding
mechanism in high luminosity AGNs. This will be done in a
quantitative
way, comparing the asymmetry indices of QSO2 hosts with
those of lower
luminosity AGNs and normal galaxies. Second, we will do a
detailed study
of the morphology of the host galaxies of both QSO types,
to determine
if they are similar, or if there is an evolutionary trend
from QSO2s to
QSO1s. The results from this project will represent an
important step in
the understanding of AGN evolution, and may also introduce
a substantial
modification to the Unified Model.
WFPC2 10877
A Snapshot Survey of the Sites of Recent, Nearby
Supernovae
During the past few years, robotic {or nearly robotic}
searches for
supernovae {SNe}, most notably our Lick Observatory
Supernova Search
{LOSS}, have found hundreds of SNe, many of them in quite
nearby
galaxies {cz < 4000 km/s}. Most of the objects were
discovered before
maximum brightness, and have follow-up photometry and
spectroscopy; they
include some of the best-studied SNe to date. We propose
to conduct a
snapshot imaging survey of the sites of some of these
nearby objects, to
obtain late-time photometry that {through the shape of the
light and
color curves} will help reveal the origin of their
lingering energy. The
images will also provide high-resolution information on
the local
environments of SNe that are far superior to what we can
procure from
the ground. For example, we will obtain color-color and
color-magnitude
diagrams of stars in these SN sites, to determine the SN
progenitor
masses and constraints on the reddening. Recovery of the
SNe in the new
HST images will also allow us to actually pinpoint their
progenitor
stars in cases where pre- explosion images exist in the
HST archive.
This proposal is an extension of our successful Cycle 13
snapshot survey
with ACS. It is complementary to our Cycle 15 archival
proposal, which
is a continuation of our long-standing program to use
existing HST
images to glean information about SN environments.
FLIGHT OPERATIONS SUMMARY:
Significant Spacecraft Anomalies: (The following are
preliminary reports
of potential non-nominal performance that will be
investigated.)
HSTARS: (None)
COMPLETED OPS REQUEST: (None)
COMPLETED OPS NOTES: (None)
SCHEDULED
SUCCESSFUL
FGS GSacq
37
37
FGS REacq
09
09
OBAD with Maneuver
88
88
SIGNIFICANT EVENTS: (None)