NASA Hubble Space Telescope Daily Report # 3677
HUBBLE SPACE TELESCOPE – Continuing to collect World Class Science
DAILY REPORT # 3677
PERIOD COVERED: DOY 231
OBSERVATIONS SCHEDULED
ACS/HRC 10130
Systemic Proper Motions of the Magellanic Clouds from Astrometry with
ACS: II. Second Epoch Images
We request second epoch observations with ACS of Magellanic Cloud
fields centered on the 40 quasars in the LMC and SMC for which we have
first epoch Cycle 11 data. The new data will determine the systemic
proper motion of the Clouds. An extensive astrometric analysis of the
first epoch data shows that follow-up observations with a two year
baseline will allow us to measure the proper motion of the clouds to
within 0.022 mas/year in each of the two orthogonal directions
{assuming that we can image 25 quasars, i.e., with a realistic
Snapshot Program completion rate}. The best weighted combination of
all previous measurements has a seven times larger error than what we
expect. We will determine the proper motion of the clouds with 2%
accuracy. When combined with HI data for the Magellanic Stream this
will constrain both the mass distribution in the Galactic Halo and
theoretical models for the origin of the Magellanic Stream. Previous
measurements are too crude for such constraints. Our data will provide
by far the most accurate proper motion measurement for any Milky Way
satellite.
ACS/HRC 10185
When does Bipolarity Impose itself on the Extreme Mass Outflows from
AGB Stars? An ACS SNAPshot Survey
Essentially all well-characterized preplanetary nebulae {PPNe} —
objects in transition between the AGB and planetary nebula
evolutionary phases – are bipolar, whereas the mass-loss envelopes of
AGB stars are strikingly spherical. In order to understand the
processes leading to bipolar mass-ejection, we need to know at what
stage of stellar evolution does bipolarity in the mass-loss first
manifest itself? Our previous SNAPshot surveys of a PPNe sample {with
ACS & NICMOS} show that roughly half our targets observed are
resolved, with well-defined bipolar or multipolar morphologies.
Spectroscopic surveys of our sample confirm that these objects have
not yet evolved into planetary nebulae. Thus, the transformation from
spherical to aspherical geometries has already fully developed by the
time these dying stars have become preplanetary nebulae. From this
new and surprising result, we hypothesize that the transformation to
bipolarity begins during the very late AGB phase, and happens very
quickly, just before, or as the stars are evolving off the AGB. We
propose to test this hypothesis quantitatively, through a SNAPshot
imaging survey of very evolved AGB stars which we believe are nascent
preplanetary nebulae; with our target list being drawn from published
lists of AGB stars with detected heavy mass-loss {from millimeter-wave
observations}. This survey is crucial for determining how and when the
bipolar geometry asserts itself. Supporting kinematic observations
using long-slit optical spectroscopy {with the Keck}, millimeter and
radio interferometric observations {with OVRO, VLA & VLBA} are being
undertaken. The results from this survey {together with our previous
work} will allow us to draw general conclusions about the onset of
bipolar mass-ejection during late stellar evolution, and will provide
crucial input for theories of post-AGB stellar evolution. Our survey
will produce an archival legacy of long-standing value for future
studies of dying stars.
ACS/HRC/WFC 10061
CCD Daily Monitor
This program consists of basic tests to monitor, the read noise, the
development of hot pixels and test for any source of noise in ACS CCD
detectors. This programme will be executed once a day for the entire
lifetime of ACS.
ACS/WFC 9744
HST Imaging of Gravitational Lenses
Gravitational lenses offer unique opportunities to study cosmology,
dark matter, galactic structure, galaxy evolution and quasar host
galaxies. They are also the only sample of galaxies selected based on
their mass rather than their luminosity or surface brightness. While
gravitational lenses can be discovered with ground-based optical and
radio observations, converting them into astrophysical tools requires
HST. We will obtain ACS/WFC V and I images and NICMOS H images of 21
new lenses never observed by HST and NICMOS H images of 16 lenses
never observed by HST in the IR. As in previous cycles, we request
that the data be made public immediately.
ACS/WFC/WFPC2 10138
Searching for the Bottom of the Initial Mass Function
The minimum mass of the Initial Mass Function {IMF} should be a direct
reflection of the physical processes that dominate in the formation of
stars and brown dwarfs. To date, the IMF has been measured down to 10
M_Jup in a few young clusters; there is no sign of a low-mass cutoff
in the data for these clusters. We propose to obtain deep images in
the SDSS i and z filters {i=26, z=25} with the ACS/WFC on HST for a
800"x1000" field in the Chamaeleon I star-forming region {2 Myr, 160
pc}. By combining these HST data {0.8, 0.9 um} with comparably deep
broad-band photometry from ground-based telescopes {1.2, 1.6, 2.2 um}
and SIRTF {3.6, 4.5, 5.8, 8.0 um}, we will measure the mass function
of brown dwarfs down to the mass of Jupiter and thus determine the
lowest mass at which objects can form in isolation in a typical star
forming cluster.
ACS/WFC/WFPC2 10273
Accurately Mapping M31’s Microlensing Population
We propose to augment an existing microlensing survey of M31 with
source identifications provided by a modest amount of ACS {and WFPC2
parallel} observations to yield an accurate measurement of the masses
responsible for microlensing in M31, and presumably much of its dark
matter. The main benefit of these data is the determination of the
physical {or "Einstein"} timescale of each microlensing event, rather
than an effective {"FWHM"} timescale, allowing masses to be determined
more than twice as accurately as without HST data. The Einstein
timescale is the ratio of the lensing cross-sectional radius and
relative velocities. Velocities are known from kinematics, and the
cross-section is directly proportional to the {unknown} lensing mass.
We cannot easily measure these quantities without knowing the
amplification, hence the baseline magnitude, which requires the
resolution of HST to find the source star. This makes a crucial
difference because M31 lens mass determinations can be more accurate
than those towards the Magellanic Clouds through our Galaxy’s halo
{for the same number of microlensing events} due to the better
constrained geometry in the M31 microlensing situation. Furthermore,
our larger survey, just completed, should yield at least 100 M31
microlensing events, more than any Magellanic survey. A small amount
of ACS+WFPC2 imaging will deliver the potential of this large database
{about 350 nights}. For the whole survey {and a delta-function mass
distribution} the mass error should approach only about 15%, or about
6% error in slope for a power-law distribution. These results will
better allow us to pinpoint the lens halo fraction, and the shape of
the halo lens spatial distribution, and allow
generalization/comparison of the nature of halo dark matter in spiral
galaxies. In addition, we will be able to establish the baseline
magnitude for about 50, 000 variable stars, as well as measure an
unprecedentedly detailed color-magnitude diagram and luminosity
function over much of M31.
FGS 10202
Resolving OB Binaries in the Carina Nebula, Resuming the Survey
In March 2002 we carried out a small, high-angular resolution survey
of some of the brightest OB stars in the Carina Nebula with FGS1r in
an attempt to resolve binary systems which had thus far evaded
detection by other techniques. Of 23 stars observed, 5 new OB binaries
were discovered with component separations ranging from 0.015"
to0.325". This yield over the spatial domain of FGS1r’s angular
resolution, coupled with published statistics of the incidence of OB
stars in short-period spectroscopic, and long-period visual binaries
suggests that the fraction of binarity or multiplicity among OB stars
is near unity. Our unexpected resolution of the prototype O2 If* star
HD 93129A as a 55 milli-arcsecond double is a case in point that great
care must be exercised when one attempt to establish the IMF and
upper-mass cuttoff at the high-mass end of the HR diagram. We propose
to resume the survey to observe a larger, statistically meaningful
sample of OB stars to establish a firm assessment of multiplicity at
the high-mass end of the IMF in these clusters. We will also
investigate the single-star/binary-star status of several
astrophysically important, individual stars in order to enable a
better understanding of the evolution of high-mass stars.
NIC1/NIC2/NIC3 8793
NICMOS Post-SAA calibration – CR Persistence Part 4
A new procedure proposed to alleviate the CR-persistence problem of
NICMOS. Dark frames will be obtained immediately upon exiting the SAA
contour 23, and every time a NICMOS exposure is scheduled within 50
minutes of coming out of the SAA. The darks will be obtained in
parallel in all three NICMOS Cameras. The POST-SAA darks will be
non-standard reference files available to users with a USEAFTER
date/time mark. The keyword ‘USEAFTER=date/time’ will also be added to
the header of each POST-SAA DARK frame. The keyword must be populated
with the time, in addition to the date, because HST crosses the SAA ~8
times per day so each POST-SAA DARK will need to have the appropriate
time specified, for users to identify the ones they need. Both the raw
and processed images will be archived as POST-SAA DARKSs. Generally we
expect that all NICMOS science/calibration observations started within
50 minutes of leaving an SAA will need such maps to remove the CR
persistence from the science images. Each observation will need its
own CRMAP, as different SAA passages leave different imprints on the
NICMOS detectors.
NIC2 10173
Infrared Snapshots of 3CR Radio Galaxies
Radio galaxies are an important class of extragalactic objects: they
are one of the most energetic astrophysical phenomena and they provide
an exceptional probe of the evolving Universe, lying typically in high
density regions but well-represented across a wide redshift range. In
earlier Cycles we carried out extensive HST observations of the 3CR
sources in order to acquire a complete and quantitative inventory of
the structure, contents and evolution of these important objects.
Amongst the results, we discovered new optical jets, dust lanes,
face-on disks with optical jets, and revealed point-like nuclei whose
properties support FR-I/BL Lac unified schemes. Here, we propose to
obtain NICMOS infrared images of 3CR sources with z<0.3 as a major
enhancement to an already superb dataset. We aim to deshroud dusty
galaxies, study the underlying host galaxy free from the distorting
effects of dust, locate hidden regions of star formation and establish
the physical characteristics of the dust itself. We will measure
frequency and spectral energy distributions of point-like nuclei,
expected to be stronger and more prevalent in the IR, seek spectral
turnovers in known synchrotron jets and find new jets. We will
strongly test unified AGN schemes and merge these data with existing
X-ray to radio observations. The resulting database will be an
incredibly valuable resource to the astronomical community for years
to come.
NIC2 10176
Coronagraphic Survey for Giant Planets Around Nearby Young Stars
A systematic imaging search for extra-solar Jovian planets is now
possible thanks to recent progress in identifying "young stars near
Earth". For most of the proposed young {<~ 30 Myrs} and nearby {<~ 60
pc} targets, we can detect a few Jupiter-mass planets as close as a
few tens of AUs from the primary stars. This represents the first time
that potential analogs of our solar system – that is planetary systems
with giant planets having semi-major axes comparable to those of the
four giant planets of the Solar System – come within the grasp of
existing instrumentation. Our proposed targets have not been observed
for planets with the Hubble Space Telescope previously. Considering
the very successful earlier NICMOS observations of low mass brown
dwarfs and planetary disks among members of the TW Hydrae Association,
a fair fraction of our targets should also turn out to posses low mass
brown dwarfs, giant planets, or dusty planetary disks because our
targets are similar to {or even better than} the TW Hydrae stars in
terms of youth and proximity to Earth. Should HST time be awarded and
planetary mass candidates be found, proper motion follow-up of
candidate planets will be done with ground-based AOs.
NIC2 10177
Solar Systems In Formation: A NICMOS Coronagraphic Survey of
Protoplanetary and Debris Disks
Until recently, despite decades of concerted effort applied to
understanding the formation processes that gave birth to our solar
system, the detailed morphology of circumstellar material that must
eventually form planets has been virtually impossible to discern. The
advent of high contrast, coronagraphic imaging as implemented with the
instruments aboard HST has dramatically enhanced our understanding of
natal planetary system formation. Even so, only a handful of evolved
disks {~ 1 Myr and older} have been imaged and spatially resolved in
light scattered from their constituent grains. To elucidate the
physical processes and properties in potentially planet-forming
circumstellar disks, and to understand the nature and evolution of
their grains, a larger spatially resolved and photometrically reliable
sample of such systems must be observed. Thus, we propose a highly
sensitive circumstellar disk imaging survey of a well-defined and
carefully selected sample of YSOs {1-10 Myr T Tau and HAeBe stars} and
{> app 10 Myr} main sequence stars, to probe the posited epoch of
planetary system formation, and to provide this critically needed
imagery. Our resolved images will shed light on the spatial
distributions of the dust in these thermally emissive disks. In
combination with their long wavelength SEDs the physical properties of
the grains will be discerned, or constrained by our photometrically
accurate surface brightness sensitivity limits for faint disks which
elude detection. Our sample builds on the success of the exploratory
GTO 7233 program, using two-roll per orbit PSF-subtracted NICMOS
coronagraphy to provide the highest detection sensitivity to the
smallest disks around bright stars which can be imaged with HST. Our
sample will discriminate between proposed evolutionary scenarios while
providing a legacy of cataloged morphologies for interpreting mid- and
far-IR SEDs that the recently launched Spitzer Space Telescope will
deliver.
WFPC2 10071
WFPC2 CYCLE 12 Supplemental Darks Part 3/3
This dark calibration program obtains 3 dark frames every day to
provide data for monitoring and characterizing the evolution of hot
pixels.
WFPC2 10170
Atmospheric Variability on Uranus and Neptune
We propose Snapshot observations of Uranus and Neptune to monitor
changes in their atmospheres on time scales of weeks, months, and
years. Uranus is rapidly approaching equinox in 2007, with another 4
degrees of latitude becoming visible every year. Recent HST
observations during this epoch {including 6818: Hammel, Lockwood, and
Rages; 7885: Hammel, Karkoschka, and Marley; 8680: Hammel, Rages,
Lockwood, and Marley; and 8634: Rages, Hammel, Lockwood, Marley, and
McKay} have revealed strongly wavelength-dependent latitudinal
structure and the presence of numerous visible-wavelength cloud
features in the northern hemisphere. Long-term ground-based
observations {Lockwood and Thompson 1999} show seasonal brightness
changes whose origins are not well understood. Recent near-IR images
of Neptune obtained using adaptive optics on the Keck Telescope
together with images from our Cycle 9 Snapshot program {8634} show a
general increase in activity at south temperate latitudes as well as
the possible development of another Great Dark Spot. Further Snapshot
observations of these two dynamic planets will elucidate the nature of
long-term changes in their zonal atmospheric bands and clarify the
processes of formation, evolution, and dissipation of discrete albedo
features.
FLIGHT OPERATIONS SUMMARY:
Significant Spacecraft Anomalies: (The following are preliminary
reports of potential non-nominal performance that will be
investigated.)
HSTAR 9516: OTA SE review of PTAS processing log for SMS 222 revealed
LOL experienced in the GS Acquisition (2,1,2) that started @
225/02:06:51Z. Both FGSs were in FLDV at 225/02:10:45Z, but at
225/02:12:21Z, both returned to SSM control and successfully achieved
FLDV by 225/02:13:15Z.
HSTAR 9517: OTA SE review of PTAS processing log for SMS 222 revealed
LOL experienced in the GS Acquisition (1,2,1) that started @
223/17:35:07Z. Both FGSs were in FLDV at 223/17:39:07Z, but at
223/02:17:40:55, both returned to SSM control and successfully
achieved FLDV by 223/17:41:39Z.
HSTAR 9518: OTA SE review of PTAS processing log for SMS 222 revealed
LOL experienced in the GS Acquisition (3,1,1) that started @
225/08:33:46Z. Both FGSs were in FLDV at 225/08:37:04Z, but at
225/08:38:46Z, both returned to SSM control and successfully achieved
FLDV by 225/08:39:40Z.
HSTAR 9519: GS Acquisition (2,1,2) @ 231/19:24:07Z failed to RGA
Control due to SRLE on FGS 1 and FGS 2. There were no FHST FM Updates
scheduled prior to the acquisition. The T2 Slew scheduled for
231/19:14:29Z had a slew angle of 29.9 degrees. The search radius for
the GS Acquisition was 70 arcsec. Due to the failure, a NICMOS 705
was received in the Status Buffer. Under investigation.
COMPLETED OPS REQs: None
OPS NOTES EXECUTED: None
SCHEDULED SUCCESSFUL FAILURE TIMES
FGS GSacq 12 11 See Hstar
# 9519
FGS REacq 07 07
FHST Update 14 14
LOSS of LOCK
SIGNIFICANT EVENTS:
SMS SA229 was reprocessed to accommodate two new Targets of
Opportunity visits from Program 10182 "Towards a Comprehensive
Understanding of Type 1a Supernovae: The Necessity of UV
Observations". Visit N1 is scheduled @ 233/05:07:06Z and Visit 2 is
scheduled @ 233/07:54:41Z. SMS intercept time is 233/03:45:19Z, with
first uplink opportunity @ 232/07:20:53Z.
