NASA Hubble Space Telescope Daily Report # 3885
HUBBLE SPACE TELESCOPE – Continuing to collect World Class Science
DAILY REPORT # 3885
PERIOD COVERED: UT June 20, 2005 (DOY 171)
OBSERVATIONS SCHEDULED
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 10198
Probing the Dynamics of the Galactic Bar through the Kinematics of
Microlensed Stars
The observed optical depths to microlensing of stars in the Galactic
bulge are difficult to reconcile with our present understanding of
Galactic dynamics. The main source of uncertainty in those comparisons
is now shifting from microlensing measurements to the dynamical models
of the Galactic bar. We propose to constrain the Galactic bar models
with proper motion observations of Bulge stars that underwent
microlensing by determining both the kinematic identity of the
microlensed sources and the importance of streaming motions. The
lensed stars are typically farther than randomly selected stars.
Therefore, our proper motion determinations for 36 targeted MACHO
events will provide valuable constraints on the dynamics of bulge
stars as a function of distance. The first epoch data for our proposed
events is already available in the HST archive so the project can be
completed within a single HST cycle. The exceptional spatial
resolution of HST is essential for completion of the project.
Constraints on the total mass in the bulge will ultimately lead to the
determination of the amount of dark matter in inner Galaxy.
ACS/HRC 10422
Resolving Changes on Triton’s Surface: Imaging over Triton’s full
longitudinal range.
We have found, from ground-based photometry, evidence of possible
seasonal surface changes on Triton which may be brought about by
geophysical activity and which have transpired since as recently as
1995. We propose to confirm and characterize these changes using the
HST ACS instrument to image Triton at UV, B, V, I and Methane-band
wavelengths over as much of its surface as visible from near Earth. By
so doing, we will determine the resurfacing rates and set model
constraints on activity and surface temperature as well as
composition. Such constraints have profound implications for our
understanding of Triton’s evolution as well as the history of other
outer solar system bodies, including outer solar system satellites
which may undergo similar geophysical processes or have similar
composition.
ACS/HRC/WFC 10389
ACS CCDs daily monitor – Cycle 13 – Part 2
This program consists of a set of basic tests to monitor, the read
noise, the development of hot pixels and test for any source of noise
in ACS CCD detectors. The files, biases and dark will be used to
create reference files for science calibration. This program will be
for the entire lifetime of ACS.
ACS/HRC/WFC 10399
Accurate and Robust Calibration of the Extragalactic Distance Scale
with the Maser Galaxy NGC4258 II
The extragalactic distance scale {EDS} is defined by a comparison of
Cepheid Period-Luminosity {PL} relations for nearby galaxies and the
LMC, whose uncertain distance is thereby the SOLE anchor. Studies of
masers orbiting the central black hole in NGC4258 have provided the
most accurate extragalactic distance ever {7.2+/-0.5 Mpc}, and new
radio data and analysis techniques will reduce the uncertainty to <
3.5% {0.07 mag} by 2005. Since this distance is well determined and
based on geometric arguments, NGC4258 can provide a much needed new
anchor for the EDS. Ultimately, the combination of an independent
measurement of H0 and measurements of CMB fluctuations {e.g., WMAP}
can be used to directly constrain cosmological parameters including
the equation of state of dark energy. In our Cycle 12 proposal, we
defined a program spanning two cycles. The Cycle 12 portion was
accepted. We have acquired WFC images and are constructing well
sampled PL relations in 3 colors {BVI}. The purpose of the Cycle 13
observations is to address systematic sources of error and is crucial
for the success of the entire program. To disentangle the effects of
reddening and metallicity, and to characterize the effects of
blending, we require 50 orbits to obtain H-band photometry
{NICMOS/NIC2} and high resolution images {ACS/HRC}.
ACS/WFC 10152
A Snapshot Survey of a Complete Sample of X-ray Luminous Galaxy
Clusters from Redshift 0.3 to 0.7
We propose a public, uniform imaging survey of a well-studied,
complete, and homogeneous sample of X-ray clusters. The sample of 73
clusters spans the redshift range between 0.3-0.7. The samples spans
almost 2 orders of magnitude of X-ray luminosity, where half of the
sample has X-ray luminosities greater than 10^44 erg/s {0.5-2.0 keV}.
These snapshots will be used to obtain a fair census of the the
morphology of cluster galaxies in the cores of clusters, to detect
radial and tangential arc candidates, to detect optical jet
candidates, and to provide an approximate estimate of the shear signal
of the clusters themselves, and potentially an assessment of the
contribution of large scale structure to lensing shear.
ACS/WFC 10472
SagDIG: a benchmark for understanding star formation in extreme
low-metallicity galaxies
A long-standing question in the field of galaxy evolution is whether
metal-poor star-forming galaxies {like I ZW 18} posses a very old {>10
Gyr} stellar population. An excellent example of such a primordial
galaxy is the Sagittarius dwarf irregular {SagDIG}. Besides being very
metal- poor, this object is exceptionally rich in atomic gas and shows
evidence of propagating star formation. Such features make of SagDIG
and ideal target for the study of star formation and its triggering
mechanism in extremely metal-poor environments. The deep, wide-field
imaging capability of ACS is able to detect an unprecedented number of
the oldest stellar population. Such data will enable the construction
of both the star formation and chemical enrichment history. In
particular, determining the epoch of formation of the first stars in
such objects places a constraint on heirarchical galaxy formation in
“bottom up” cosmologies.
ACS/WFC/NIC3 10632
Searching for galaxies at z>6.5 in the Hubble Ultra Deep Field
We propose to obtain deep ACS {F606W, F775W, F850LP} imaging in the
area of the original Hubble Ultra Deep Field NICMOS parallel fields
and – through simultaneous parallel observations – deep NICMOS {F110W,
F160W} imaging of the ACS UDF area. Matching the extreme imaging depth
in the optical and near-IR bands will result in seven fields with
sufficiently sensitive multiband data to detect the expected typical
galaxies at z=7 and 8. Presently no such a field exist. Our combined
optical and near-IR ultradeep fields will be in three areas separated
by about 20 comoving Mpc at z=7. This will allow us to give a first
assessment of the degree of cosmic variance. If reionization is a
process extending over a large redshift interval and the luminosity
function doesn’t evolve strongly beyond z=6, these data will allow us
to identify of the order of a dozen galaxies at 6.5
be an indication that the bulk of reionization is done by galaxies at
z=6. By spending 204 orbits of prime HST time we will capitalize on
the investment of 544 prime orbits already made on the Hubble Ultra
Deep Field {UDF}. We have verified that the program as proposed is
schedulable and that it will remain so even if forced to execute in
the 2-gyro mode. The data will be non-proprietary and the reduced
images will be made public within 2 months from the completion of the
observations.
NIC1/NIC2/NIC3 8792
NICMOS Post-SAA calibration – CR Persistence Part 3
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.
NIC3/ACS/WFC 10404
The Nature of Protocluster Galaxies at z=2.16: Morphology-Density and
Color-Magnitude Relations
To establish the epoch when galaxy environment manifests itself as a
large-scale evolutionary process, we propose to extend the study of
galaxy colors and morphologies to a protocluster at z=2.16. Here the
universe is only 3 Gyrs old and significant differences are expected
between scenarios favoring a morphology-radius relation over a
morphology-density relation. In addition, because the fractional age
differences among cluster galaxies are larger, study of the color-
magnitude relation provides considerable leverage for determining the
epoch of early-type galaxy formation. To facilitate direct comparison
to studies at lower redshift, one must probe the same rest-frame
wavelengths with high photometric accuracy and at similar physical
scales. Its near-infrared photometric stability {low, constant
background} and ability to image large areas of sky at high
angular-resolution {compared to adaptive optics} makes HST/NICMOS
ideal for this program. Six pointings of NICMOS camera 3 will result
in rest-frame optical, high resolution images of 16 confirmed
protocluster members, and an additional 60 candidate protocluster
members including 29 EROs. These galaxies were selected with a variety
of techniques and span a range of projected radii within the
protocluster. The proposed observations constitute a unique
opportunity to extend the study of galaxies in overdense regions to an
early time in cosmic history.
WFPC2 10356
WFPC2 Cycle 13 Decontaminations and Associated Observations
This proposal is for the monthly WFPC2 decons. Also included are
instrument monitors tied to decons: photometric stability check, focus
monitor, pre- and post-decon internals {bias, intflats, kspots, &
darks}, UV throughput check, VISFLAT sweep, and internal UV flat
check.
FLIGHT OPERATIONS SUMMARY:
Significant Spacecraft Anomalies: (The following are preliminary
reports of potential non-nominal performance that will be
investigated.)
HSTARS:
9857 – Gsacq(1,3,1) results in finelock backup (3,0,3) @171/1213z The
GSacq(1,3,1)scheduled for 171/12:13:08 – 12:20:31 resulted in finelock
backup(3,0,3)using FGS-3, due to scan step limit exceeded on FGS-1
during walkdown. Prior FM updates scheduled at 171/12:06 and 12:09
showed small error.
COMPLETED OPS REQUEST:
17452-0 – GenSlew for Prop#10425 Slot#12 @171/1321
17453-0 – GenSlew for Prop#10425 Slot#01 @171/1330
COMPLETED OPS NOTES: (None)
SCHEDULED SUCCESSFUL FAILURE TIMES FGS Gsacq 11 11 FGS Reacq 07 07 FHST Update 19 19 LOSS of LOCK
SIGNIFICANT EVENTS: (None)
