HUBBLE SPACE TELESCOPE - Continuing to collect World Class
Science
DAILY REPORT #4816
PERIOD COVERED: 5am March 20 - 5am March 23, 2009 (DOY
079/0900z-082/0900z)
OBSERVATIONS SCHEDULED
WFPC2 11987
The Recent Star Formation History of SINGS Galaxies
The Spitzer Legacy project SINGS provided a unique view of
the current
state of star formation and dust in a sample of galaxies
of all Hubble
types. This multi-wavelength view allowed the team to
create current
star formation diagnostics that are independent of the
dust content and
increased our understanding of the dust in galaxies. Even
so, using the
SINGS data alone we can only make rough estimates of the recent
star
formation history of these galaxies. The lack of U-band
observations
means that it is impossible to estimate the ages of young
clusters. In
addition, the low resolution of the Spitzer and
ground-based
observations means that what appear to be individual
Spitzer sources can
actually be composed of many individual clusters with
varying ages. In
this proposal we plan to address this missing area in
SINGS by obtaining
high-resolution WFPC2 UBVI observations to accurately find
and determine
the ages of the young stellar clusters in a subset of the
SINGS
galaxies. These observations will greatly enhance the
legacy value of
the SINGS observations while also directly answering
questions
pertaining to star formation in galaxies.
WFPC2 11986
Completing HST's Local Volume Legacy
Nearby galaxies offer one of the few laboratories within
which stellar
populations can be tied to multi-wavelength observations.
They are thus
essential for calibrating and interpreting key
astrophysical
observables, such as broad-band luminosities, durations
and energy input
from starbursts, and timescales of UV, H-alpha, and FIR
emission. The
study of stellar populations in nearby galaxies requires
high-resolution
observations with HST, but HST's legacy for this limited
set of galaxies
remains incomplete.
As a first attempt to establish this legacy, The ACS
Nearby Galaxy
Survey Treasury (ANGST) began observations in late 2006.
ANGST was
designed to carry out a uniform multi-color survey of a
volume-limited
sample of ~70 nearby galaxies that could be used for
systematic studies
of resolved stellar populations. The resulting data
provide nuanced
constraints on the processes which govern star formation
and galaxy
evolution, for a well-defined population of galaxies. All photometry
for
the survey has been publicly released.
However, the failure of ACS 4.5 months after ANGST began
taking data led
to a drastic reduction in the planned survey. The loss is
two-fold.
First, the goals of completeness and uniformity were
greatly
compromised, impacting global comparison studies. Second,
the variety of
observed star formation histories was reduced. Given that
we have never
found two galaxies with identical star formation
histories, and fully
sampling the population allows us to catch those few
systems whose star
formation rates and metallicities place the strongest
constraints on key
astrophysical processes.
Here we propose WFPC2 observations of all remaining
galaxies within the
Local Volume (D<3.5Mpc) for which current HST
observations are
insufficient for meaningful stellar population studies. We
will use
these observations for research on the star formation
histories of
individual galaxies and the Local Volume, detailed
calibrations of star
formation rate indicators, and the durations of
starbursts. We will also
make them publicly available through the ANGST archive to
support future
research. The proposed observations will finally complete
a lasting
legacy of HST
ACS/SBC 11980
Deep FUV Imaging of Cooling Flow Clusters
We propose to take deep ACS FUV images of a carefully
selected sample of
19 bright central galaxies in nearby galaxy clusters. This
program is
the last critical element of a comprehensive investigation
of the impact
of stellar and AGN feedback on the local galaxy cluster
environment. The
HST images will complement new, high-resolution, Halpha
images obtained
with the recently commissioned Maryland-Magellan Tunable
Filter (MMTF)
on the Baade 6.5m telescope, archival Chandra, VLA, and
GALEX data, and
on-going H2/NIR observations. The MMTF data have revealed
unsuspected
filamentary complexes in several systems. The GALEX data
often show
hints of extended NUV and FUV emission on a similar scale,
but their
poor spatial resolution prevents meaningful comparison
with the MMTF
data. The HST data will provide this much needed gain in
resolution. The
combined radio-H2-Halpha-FUV-X-ray dataset will allow us
to derive with
unprecedented precision the role of the AGN, hot stars,
shocks, and
relativistic particles on the excitation and
thermodynamics of the
multi-phase intracluster and interstellar media in these
systems. This
is an important question since the formation and evolution
of most
cluster galaxies have likely been affected by these
processes.
WFPC2 11976
Particle Separation in and Expansion of the Dust Arcs of
the Young Star
V1331 Cyg
HST-WFPC2 imaging of the young star V1331 Cyg revealed
several dust arcs
seen in scattered light which were caused by short-lived
strong winds
arising from FU Ori-like outbursts. Most notably the
brightest outer arc
is encircled by an expanding CO ring which implies that
the otherwise
extremely well mixed gas and dust components were
separated according to
particle mass. This is presumably due to the dependence of
the wind ram
pressure on the ratio of particle cross section and mass
as well as the
brief acceleration period. Thus, we suspect that a FU Ori
outburst acts
as a cosmic mass spectrometer. In order to verify this
hypothesis, we
apply for 2nd epoch imaging to reveal the color gradient
across the
bright dust arc which will be induced by the grain
sorting. Furthermore,
the current imagery will allow us to prove directly the
expansion of the
arc by measuring its proper motion. The proposed
observations represent
new diagnostics for what concerns studies of young stellar
objects.
WFPC2 11975
UV Light from Old Stellar Populations: a Census of UV
Sources in
Galactic Globular Clusters
In spite of the fact that HST has been the only operative
high-resolution eye in the UV-window over the last 18
years, no
homogeneous UV survey of Galactic globular clusters (GGCs)
has been
performed to date. In order to fill this gap in the
stellar population
studies, we propose a program that exploits the unique
capability of the
WFPC2 and the SBC in the far-/mid- UV for securing deep UV
imaging of 46
GGCs. The proposed observations will allow to study with
unprecedented
accuracy the hottest GGC stars, comprising the extreme
horizontal branch
(HB) stars and their progeny (the so-called AGB-manque',
and Post-early
AGB stars), and "exotic stellar populations"
like the blue straggler
stars and the interacting binaries. The targets have been
selected to
properly sample the GGC metallicity/structural parameter
space, thus to
unveil any possible correlation between the properties of
the hot
stellar populations and the cluster characteristics. In
addition, most
of the targets have extended HB "blue tails",
that can be properly
studied only by means of deep UV observations, especially
in the far-UV
filters like the F160BW, that is not foreseen on the WFC3.
This data
base is complemented with GALEX observations in the
cluster outermost
regions, thus allowing to investigate any possible trend
of the
UV-bright stellar types over the entire radial extension
of the
clusters. Although the hottest GGC stars are just a small
class of
"special" objects, their study has a broad
relevance in the context of
structure formation and chemical evolution in the early
Universe,
bringing precious information on the basic star formation
processes and
the origin of blue light from galaxies. Indeed, the
proposed
observations will provide the community with an
unprecedented data set
suitable for addressing a number of still open
astrophysical questions,
ranging from the main drivers of the HB morphology and the
mass loss
processes, to the origin of the UV upturn in elliptical
galaxies, the
dating of distant systems from integrated light, and the
complex
interplay between stellar evolution and dynamics in dense
stellar
aggregates. In the spirit of constructing a community
resource, we
entirely waive the proprietary period for these
observations.
WFPC2 11944
Binaries at the Extremes of the H-R Diagram
We propose to use HST/Fine Guidance Sensor 1r to survey
for binaries
among some of the most massive, least massive, and oldest
stars in our
part of the Galaxy. FGS allows us to spatially resolve
binary systems
that are too faint to observe using ground-based, speckle
or optical
long baseline interferometry, and too close to resolve
with AO. We
propose a SNAP-style program of single orbit FGS TRANS
mode observations
of very massive stars in the cluster NGC 3603, luminous
blue variables,
nearby low mass main sequence stars, cool subdwarf stars,
and white
dwarfs. These observations will help us to (1) identify
systems suitable
for follow up studies for mass determination, (2) study
the role of
binaries in stellar birth and in advanced evolutionary
states, (3)
explore the fundamental properties of stars near the main
sequence-brown
dwarf boundary, (4) understand the role of binaries for
X-ray bright
systems, (5) find binaries among ancient and nearby
subdwarf stars, and
(6) help calibrate the white dwarf mass - radius relation.
FGS 11943
Binaries at the Extremes of the H-R Diagram
We propose to use HST/Fine Guidance Sensor 1r to survey
for binaries
among some of the most massive, least massive, and oldest
stars in our
part of the Galaxy. FGS allows us to spatially resolve
binary systems
that are too faint for ground-based, speckle or optical
long baseline
interferometry, and too close to resolve with AO. We
propose a
SNAP-style program of single orbit FGS TRANS mode
observations of very
massive stars in the cluster NGC 3603, luminous blue
variables, nearby
low mass main sequence stars, cool subdwarf stars, and
white dwarfs.
These observations will help us to (1) identify systems
suitable for
follow up studies for mass determination, (2) study the
role of binaries
in stellar birth and in advanced evolutionary states, (3)
explore the
fundamental properties of stars near the main
sequence-brown dwarf
boundary, (4) understand the role of binaries for X-ray
bright systems,
(5) find binaries among ancient and nearby subdwarf stars,
and (6) help
calibrate the white dwarf mass - radius relation.
FGS 11788
The Architecture of Exoplanetary Systems
Are all planetary systems coplanar? Concordance cosmogony
makes that
prediction. It is, however, a prediction of extrasolar
planetary system
architecture as yet untested by direct observation for
main sequence
stars other than the Sun. To provide such a test, we
propose to carry
out FGS astrometric studies on four stars hosting seven
companions. Our
understanding of the planet formation process will grow as
we match not
only system architecture, but formed planet mass and true
distance from
the primary with host star characteristics for a wide
variety of host
stars and exoplanet masses.
We propose that a series of FGS astrometric observations
with
demonstrated 1 millisecond of arc per-observation
precision can
establish the degree of coplanarity and component true
masses for four
extrasolar systems: HD 202206 (brown dwarf+planet); HD
128311
(planet+planet), HD 160691 = mu Arae (planet+planet), and
HD 222404AB =
gamma Cephei (planet+star). In each case the companion is
identified as
such by assuming that the minimum mass is the actual mass.
For the last
target, a known stellar binary system, the companion orbit
is stable
only if coplanar with the AB binary orbit.
FGS 11704
The Ages of Globular Clusters and the Population II
Distance Scale
Globular clusters are the oldest objects in the universe
whose age can
be accurately determined. The dominant error in globular
cluster age
determinations is the uncertain Population II distance
scale. We propose
to use FGS 1r to obtain parallaxes with an accuracy of 0.2
milliarcsecond for 9 main sequence stars with [Fe/H] <
-1.5. This will
determine the absolute magnitude of these stars with
accuracies of 0.04
to 0.06mag. This data will be used to determine the
distance to 24
metal-poor globular clusters using main sequence fitting.
These
distances (with errors of 0.05 mag) will be used to determine
the ages
of globular clusters using the luminosity of the subgiant
branch as an
age indicator. This will yield absolute ages with an
accuracy 5%, about
a factor of two improvement over current estimates.
Coupled with
existing parallaxes for more metal-rich stars, we will be
able to
accurately determine the age for globular clusters over a
wide range of
metallicities in order to study the early formation
history of the Milky
Way and provide an independent estimate of the age of the
universe.
The Hipparcos database contains only 1 star with [Fe/H]
< -1.4 and an
absolute magnitude error less than 0.18 mag which is
suitable for use in
main sequence fitting. Previous attempts at main sequence
fitting to
metal-poor globular clusters have had to rely on theoretical
calibrations of the color of the main sequence. Our HST
parallax program
will remove this source of possible systematic error and
yield distances
to metal-poor globular clusters which are significantly
more accurate
than possible with the current parallax data. The HST
parallax data will
have errors which are 10 times smaller than the current
parallax data.
Using the HST parallaxes, we will obtain main sequence
fitting distances
to 11 globular clusters which contain over 500 RR Lyrae
stars. This will
allow us to calibrate the absolute magnitude of RR Lyrae
stars, a
commonly used Population II distance indicator.
WFPC2 11343
Identifying the host galaxies for optically dark gamma-ray
bursts
We propose to use the high spatial resolution capabilities
of Chandra to
obtain precise positions for a sample of Gamma-ray bursts
(GRBs) with no
optical afterglows, where the optical light is suppressed
relative to
the X-ray flux. These bursts are likely to be highly
obscured and may
have different environments from the optically bright
GRBs. Our Chandra
observations will (unlike Swift-XRT positions) allow for
the unique
identification of a host galaxy. To locate these host
galaxies we will
follow up our Chandra positions with deep optical and IR
observations
with HST. The ultimate aim is to understand any
differences between the
host galaxies of optically dark and bright GRBs, and how
these affect
the use of GRBs as tracers of starformation and galaxy
evolution at high
redshift.
WFPC2 11316
HST Cycle 16 & Pre-SM4 Optical Monitor
This is a continuation of the Cycle 15 & pre-SM4
Optical Monitor, 11020.
Please see that proposal for a more complete description
of the
observing strategy. The 6 visits comprising this proposal
observe two
single standard stars with WFPC2/PC in order to establish
overall OTA
focal length for the purposes of focus maintenance. The
goal of this
monitoring before SM4 is to establish a best estimate of
the OTA focus
entering SMOV.
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.
FLIGHT OPERATIONS SUMMARY:
Significant Spacecraft Anomalies: (The following are
preliminary reports
of potential non-nominal performance that will be
investigated.)
HSTARS:
11734 - REAcq(1,2,2) scheduled at 082/04:04:45z failed due
to scan step
limited exceed on FGS1.
Observation effected WFPC 23-24, Proposal ID# 11975 &
11302.
COMPLETED OPS REQUEST: (None)
COMPLETED OPS NOTES: (None)
SCHEDULED
SUCCESSFUL
FGS
GSAcq
15
15
FGS
REAcq
23
22
OBAD with Maneuver
76 76
SIGNIFICANT EVENTS: (None)