Notice:
Due to the conversion of some ACS WFC or HRC observations into
WFPC2,
or NICMOS observations after the loss of ACS CCD science
capability
in January, there may be an occasional discrepancy between a
proposal's
listed (and correct) instrument usage and the abstract that
follows
it.
HUBBLE
SPACE TELESCOPE - Continuing to collect World Class Science
DAILY
REPORT # 4449
PERIOD
COVERED: UT September 17, 2007 (DOY 260)
OBSERVATIONS
SCHEDULED
WFPC2
10789
The
Role of Environment in the Formation of Dwarf Galaxies
Clusters
of galaxies contain an overdensity of dwarfs compared to the
field.
Within galaxy clusters there is also a correlation between the
overdensity
of dwarfs and local galaxy density, such that areas of lower
galaxy
density contain more dwarfs per giant. The origin of these
'extra'
dwarfs is unknown, but a large fraction of them did not form
through
standard collapses early in the universe. Some dwarf ellipticals
in
clusters have metal rich and young {< 6 Gyr} stellar populations
while
others contain old metal poor populations, suggesting multiple
formation
mechanisms and time scales. We propose to test the idea that
dwarfs
descend from galaxies accreted into clusters during the past 8
Gyr
by correlating ages and metallicities of dwarfs with their internal
structures
- spiral arms, bars, and disks. If dwarfs originate from more
massive
galaxies then these features should be common in metal rich and
young
dwarfs. On the other hand, if no correlation is found it would
suggest
that dwarfs form through in-situ collapses of gas in the
intragalactic
medium after the universe was reionized.
WFPC2
11027
Visible
Earth Flats
This
proposal monitors flatfield stability. This proposal obtains
sequences
of Earth streak flats to construct high quality flat fields
for
the WFPC2 filter set. These flat fields will allow mapping of the
OTA
illumination pattern and will be used in conjunction with previous
internal
and external flats to generate new pipeline superflats. These
Earth
flats will complement the Earth flat data obtained during cycles
4-14.
WFPC2
11081
RR
Lyrae stars in M31 Globular Clusters: How did the M31 Spiral Galaxy
Form?
The
pulsation properties of the RR Lyrae stars in the globular clusters
of
the Andromeda galaxy {M31} have the potential to provide essential
insight
on the first epoch of the galaxy formation and to trace the
merging
episodes that led to the assembly of M31. Their mean periods
along
with the cluster metallicities can provide an independent estimate
of
the M31 cluster ages and, in turn, of the time scale of the M31 halo
formation,
by comparison with their Milky Way counterparts. We will
observe
RR Lyrae stars in 6 appropriately selected globular clusters of
M31
using WFPC2 to derive periods, light curves, and physical parameters
of
these eyewitnesses of the first epochs of the M31 formation.
WFPC2
11084
Probing
the Least Luminous Galaxies in the Local Universe
We
propose to obtain deep color-magnitude data of eight new Local Group
galaxies
which we recently discovered: Andromeda XI, Andromeda XII, and
Andromeda
XIII {satellites of M31}; Canes Venatici I, Canes Venatici II,
Hercules,
and Leo IV {satellites of the Milky Way}; and Leo T, a new
"free-floating"
Local Group dwarf spheroidal with evidence for recent
star
formation and associated H I gas. These represent the least
luminous
galaxies known at *any* redshift, and are the only accessible
laboratories
for studying this extreme regime of galaxy formation. With
deep
WFPC-2 F606W and F814W pointings at their centers, we will
determine
whether these objects contain single or multiple age stellar
populations,
as well as whether these objects display a range of
metallicities.
WFPC2
11178
Probing
Solar System History with Orbits, Masses, and Colors of
Transneptunian
Binaries
The
recent discovery of numerous transneptunian binaries {TNBs} opens a
window
into dynamical conditions in the protoplanetary disk where they
formed
as well as the history of subsequent events which sculpted the
outer
Solar System and emplaced them onto their present day heliocentric
orbits.
To date, at least 47 TNBs have been discovered, but only about a
dozen
have had their mutual orbits and separate colors determined,
frustrating
their use to investigate numerous important scientific
questions.
The current shortage of data especially cripples scientific
investigations
requiring statistical comparisons among the ensemble
characteristics.
We propose to obtain sufficient astrometry and
photometry
of 23 TNBs to compute their mutual orbits and system masses
and
to determine separate primary and secondary colors, roughly tripling
the
sample for which this information is known, as well as extending it
to
include systems of two near-equal size bodies. To make the most
efficient
possible use of HST, we will use a Monte Carlo
technique to
optimally
schedule our observations.
WFPC2
11229
SEEDS:
The Search for Evolution of Emission from Dust in Supernovae with
HST
and Spitzer
The
role that massive stars play in the dust content of the Universe is
extremely
uncertain. It has long been hypothesized that dust can
condense
within the ejecta of supernovae {SNe}, however there is a
frustrating
discrepancy between the amounts of dust found in the early
Universe,
or predicted by nucleation theory, and inferred from SN
observations.
Our SEEDS collaboration has been carefully revisiting the
observational
case for dust formation by core-collapse SNe, in order to
quantify
their role as dust contributors in the early Universe. As dust
condenses
in expanding SN ejecta, it will increase in optical depth,
producing
three simultaneously observable phenomena: {1} increasing
optical
extinction; {2} infrared {IR} excesses; and {3} asymmetric
blue-shifted
emission lines. Our SEEDS collaboration recently reported
all
three phenomena occurring in SN2003gd, demonstrating the success of
our
observing strategy, and permitting us to derive a dust mass of up to
0.02
solar masses created in the SN. To advance our understanding of the
origin
and evolution of the interstellar dust in galaxies, we propose to
use
HST's WFPC2 and NICMOS instruments plus Spitzer's photometric
instruments
to monitor ten recent core- collapse SNe for dust formation
and,
as a bonus, detect light echoes that can affect the dust mass
estimates.
These space-borne observations will be supplemented by
ground-
based spectroscopic monitoring of their optical emission line
profiles.
These observations would continue our 2-year HST and Spitzer
monitoring
of this phenomena in order to address two key questions: Do
all
SNe produce dust? and How much dust do they produce? As all the SN
are
within 15 Mpc, each SN stands an excellent chance of detection with
HST
and Spitzer and of resolving potential light echoes.
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
06
06
FGS
REacq
08
08
OBAD
with Maneuver 30
30
SIGNIFICANT
EVENTS: (None)