HUBBLE SPACE TELESCOPE - Continuing to collect World Class
Science
DAILY REPORT #4841
PERIOD COVERED: 5am April 24 - 5am April 27, 2009 (DOY
114/0900z-117/0900z)
OBSERVATIONS SCHEDULED
WFPC2 11983
An Imaging Survey of Protoplanetary Disks and Brown Dwarfs
in the
Chamaeleon I Region
We propose to carry out a HST/WFPC2 survey of young brown
dwarfs, Class
I and Class II sources in the Chamaelon I region, one of
the
best-studied star-forming regions, in order to investigate
the link
between disk evolution and the formation of
substellar-mass objects. We
will use deep broad-band imaging in the I and z-equivalent
HST bands to
unveil the unknown population of substellar binary
companions, down to a
few Jupiter masses for separations of a few tens of AU. We
will also
perform narrow-band imaging to directly detect accreting
circumstellar
disks and jets around brown dwarfs, Class-I and class-II
objects.
Chamaelon I is nearly coeaval of Orion (~1-2Myr) but at
~1/3 its
distance, allowing 3x higher resolution and 10x more flux
for comparable
objects. Unlike Orion, low-mass objects and protoplanetary
disks in
Chamaeleon I have been extensively studied with Spitzer,
but not yet
with the HST. The Chamaeleon I region is an ideal HST
target, as it lies
in the CVZ of the HST and therefore it is easily
accessible any time of
the year with long orbits.
ACS/SBC 11982
Spanning the Reionization History of IGM Helium: a Large
and Efficient
HST Spectral Survey of Far-UV-Bright Quasars
The reionization of IGM helium is thought to have occurred
at redshifts
of z=3 to 4. Detailed studies of HeII Lyman-alpha
absorption toward a
handful of QSOs at 2.7<z<3.3 demonstrated the high
potential of such IGM
probes, but the small sample size and redshift range limit
confidence in
cosmological inferences. The requisite unobscured
sightlines to high-z
are extremely rare, but we've cross-correlated 10, 000
z>2.8 SDSS DR7
(and other) quasars with GALEX GR4 UV sources to obtain
550 new, high
confidence, sightlines potentially useful for HST HeII
studies; and in
cycle 15-16 trials we demonstrated the efficacy of our
SDSS/GALEX
selection approach identifying 9 new HeII quasars at
unprecedented 67%
efficiency. We propose the first far-UV-bright HeII quasar
survey that
is both large in scale and also efficient, via 2-orbit
reconnaissance
ACS/SBC prism spectra toward a highly select subset of 40
new SDSS/GALEX
quasars at 3.1<z<5.1. These will provide a community
resource list that
includes 5 far-UV-bright (restframe) HeII sightlines in
each of 8
redshift bins spanning 3.1<z<3.9 (and perhaps
several objects at z>4),
enabling superb post-SM4 follow-up spectra with COS or
STIS. But
simultaneously and independent of any SM4 uncertainties,
we will hereby
directly obtain 10-orbit UV spectral stacks from the 5
HeII quasars in
each of the 8 redshift bins to trace the reionization
history of IGM
helium over at least
3.1<z<3.9. These spectral stacks will average over
cosmic variance and individual object pathology. Our new
high-yield HeII
sightline sample and spectral stacks, covering a large
redshift range,
will allow confident conclusions about the spectrum and
evolution of the
ionizing background, the evolution of HeII opacity, the
density of IGM
baryons, and the epoch of helium reionization.
WFPC2 11979
WFPC2 Imaging of Fomalhaut b: Determining its Orbit and
Testing for
H-alpha Emission
Fomalhaut is a bright nearby star that harbors a belt of
dusty material
with a morphology that has been used to predict the
presence of a
shepherding planet. With ACS/HRC coronagraphy, we have
achieved the
direct detection of a planet candidate (Fomalhaut b) in
F606W and F814W.
The planet candidate lies 18 AU interior to the dust belt
and we detect
counterclockwise orbital motion in two epochs of
observations (2004 and
2006). Fomalhaut b has mass no greater than three Jupiter
masses based
on an analysis of its luminosity, including non-detections
at infrared
wavelengths, and the dynamical argument that a
significantly more
massive object would disrupt the dust belt. Variability at
optical
wavelengths and the brightness in the F606W passband
suggest additional
sources of luminosity such as starlight reflected from a
circumplanetary
ring system. A second possibility that has been invoked
for substellar
objects is a significant contribution of H-alpha emission.
Here we
propose follow-up WFPC2 observations to test the
possibility that the
F606W flux is contaminated by H-alpha emission. We
demonstrate that the
detection of Fomalhaut b using WFPC2 is feasible using
roll
deconvolution. Furthermore, a detection of Fomalhaut b in
2009 will
provide a crucial third epoch for astrometry. With the
existing two
epochs of data, the orbit of Fomalhaut b cannot be
determined uniquely.
The third epoch will be used to test the prediction of
apsidal alignment
and more accurately determine the dynamical mass of
Fomalhaut b. If
apsidal mis-alignment is found between the planet and the
belt, this
result would point to the existence of still other planets
lurking
unseen in the Fomalhaut system.
WFPC2 11978
Luminous and Dark Matter in Disk Galaxies from Strong
Lensing and
Stellar Kinematics
The formation of realistic disk galaxies within the LCDM
paradigm is
still an unsolved problem. Theory is only now beginning to
make
predictions for how dark matter halos respond to galaxy
formation and
for the properties of disk galaxies. Measuring the density
profiles of
dark matter halos on galaxy scales is therefore a strong
test for the
standard paradigm of galaxy formation, offering great
potential for
discovery. However, from an observational point of view,
the degeneracy
between the stellar and dark matter contributions to
galaxy rotation
curves remains a major road block. Strong gravitational
lensing, when
coupled to spatially-resolved kinematics and stellar
population models,
can solve this long-standing problem. Unfortunately, this
joint
methodology could not be exploited so far due to the paucity
of known
edge-on spiral lenses. Exploiting the full SDSS-DR7
archive we have
identified a new sample of exactly these systems. We
propose multi-color
HST imaging to confirm and measure a sample of twenty
spiral lenses,
covering a range of bulge to disk ratios. By combining
dynamical lensing
and stellar population information for this unique sample
we will
deliver the first statistical constraints on halos and
disk properties,
and a new stringent test of disk galaxy formation
theories.
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 11790
HST/FGS Astrometric Search for Young Planets Around Beta
Pic and AU Mic
AU Mic is a nearby Vega-type debris disk star. Its disk
system has been
spatially resolved in exquisite detail, predominantly via
the ACS
coronagraph and WFPC-2 cameras onboard HST. These images
exhibit a
wealth of morphological features which provide compelling
indirect
evidence that AU Mic likely harbors short-period planetary
body(ies). We
propose to use the superlative astrometric capabilities of
HST/FGS to
directly detect these planets, hence provide the first
direct planet
detection in a Vega-type system whose disk has been imaged
at high
spatial resolution.
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 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 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.
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
23
23
FGS
REAcq
15
15
OBAD with Maneuver
72
72
SIGNIFICANT EVENTS: (None)