Status Report

NASA Hubble Space Telescope Daily Report # 3486 (part 2)

By SpaceRef Editor
November 10, 2003
Filed under , ,

ACS 9831

Multiplicity among brown dwarfs in the Pleiades cluster

We have compiled a sample of 32 confirmed brown dwarfs in the Pleiades
cluster. We propose to observe this sample with HST/ACS in SNAPSHOT
mode in order to search for very low mass multiple systems. Our goals
are: 1} to determine the occurrence and frequency of binary systems
among substellar objects, which hold important clues to the formation
and evolution mechanism{s} of ultracool and brown dwarfs, 2} to get an
estimate of the Initial Mass Function {IMF} at very low masses, which
is still unknown and very much needed to be corrected for binarity, 3}
to compare the distribution of multiple systems in young open clusters
and in the field.

NIC2 9801

Are OH/IR Stars the Youngest post-AGB stars? A NICMOS Imaging 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. We have recently hypothesized that most OH/IR stars
{evolved mass- losing stars with OH maser emission} are very young
PPNe. We are conducting a multiwavelength survey program of imaging
and spectroscopic observations of such objects, using a large,
morphologically unbiased sample selected using IRAS 12-to-25 micron
colors. Our ongoing HST/SNAP imaging survey of the optically bright
half of this sample with WFPC2 and ACS is highly successful: 19/32
objects observed are extended with bipolar/multipolar shapes
{remaining objects are unresolved}. Slightly more than 50% of our
sample are optically too faint or undetected but have strong near-IR
counterparts — we therefore propose a NICMOS SNAPshot imaging survey
of these optically-faint OH/IR stars. These observations are crucial
for determining how and when the bipolar geometry asserts itself. The
results from our NICMOS survey {together with the WFPC2/ACS survey}
will allow us to draw general conclusions about the onset of bipolar
mass-ejection during late stellar evolution. Our complementary program
of interferometric mapping of the OH maser emission in our sources is
yielding kinematic information with spatial resolution comparable to
that in the HST images. The HST/radio data will provide crucial input
for theories of post-AGB stellar evolution. In addition, these data
will also indicate whether the multiple concentric rings, “searchlight
beams”, and truncated equatorial disks recently discovered with HST
in a few PPNe, are common or rare phenomena.

ACS/WFC 9788

A Narrow-band Snapshot Survey of Nearby Galaxies

We propose to use ACS/WFC to conduct the first comprehensive HST
narrow-band {H-alpha + [N II]} imaging survey of the central regions
of nearby bulge-dominated disk {S0 to Sbc} galaxies. This survey will
cover, at high angular resolution extending over a large field, an
unprecedented number of galaxies representing many different
environments. It will have important applications for many
astrophysical problems of current interest, and it will be an
invaluable addition to the HST legacy. The observations will be
conducted in snapshot mode, drawing targets from a complete sample of
145 galaxies selected from the Palomar spectroscopic survey of nearby
galaxies. Our group will use the data for two primary applications.
First, we will search for nuclear emission-line disks suitable for
future kinematic measurements with STIS, in order to better constrain
the recently discovered relations between black hole mass and bulge
properties. Preliminary imaging of the type proposed here must be
done, sooner or later, if we are to make progress in this exciting new
field. Second, we will investigate a number of issues related to
extragalactic star formation. Specifically, we will systematically
characterize the properties of H II regions and super star clusters on
all galactic scales, from circumnuclear regions to the large-scale

STIS 9786

The Next Generation Spectral Library

We propose to continue the Cycle 10 snapshot program to produce a Next
Generation Spectral Library of 600 stars for use in modeling the
integrated light of galaxies and clusters. This program is using the
low dispersion UV and optical gratings of STIS. The library will be
roughly equally divided among four metallicities, very low {[Fe/H] lt
-1.5}, low {[Fe/H] -1.5 to -0.5}, near-solar {[Fe/H] -0.3 to 0.1}, and
super-solar {[Fe/H] gt 0.2}, well-sampling the entire HR-diagram in
each bin. Such a library will surpass all extant compilations and have
lasting archival value, well into the Next Generation Space Telescope
era. Because of the universal utility and community-broad nature of
this venture, we waive the entire proprietary period.


Probing Outflowing Winds from the Galactic Center

We propose to use two extragalactic sightlines to probe our own
Galaxy’s “starburst” wind emanating from the Galactic Center. While
new infrared imaging and spectroscopy have detected massive stars and
very recent {<3x10^6 yrs} star formation in the Galactic Center region, only indirect evidence {e.g., radio loops and arcs, bi-conical cavity edges seen in the mid-IR} exists for a wind. However, these winds are routinely detected from starbursts in other galaxies. Far-UV STIS echelle spectroscopy {E140M} of two targets on either side of the Galactic Center at {l, b}={350,-33} and {349, 55} will allow us to map the kinematics of outflowing gas in high ionization species of N V, Si IV and C IV. Similar spectra of distant {1.5-5 kpc}, bright B stars in the same regions of the sky will allow us to remove foreground contaminating components due to the Sco-Cen OB associations. Lower resolution STIS first-order and FUSE spectra show highly redshifted gas in N V and O VI respectively along these sightlines; these new observations will provide three times better spectral resolution {7-10 km/s in the 1185-1580A region} so that the kinematic signature of the outflow can definitely be detected. The foreground stars will allow us to determine whether the outflow is from the Galactic Center or the Sco-Cen OB associations. Absorption line column densities will be used to estimate the outflowing mass and energy by assuming a metallicity and ionizing source for the gas.

ACS/WFC 9765

The Dusty ISM Substructure in Nearby Spiral Galaxies

We propose an ACS V&I imaging snapshot survey of all nearby edge-on
spiral galaxies in order to measure the small scale structures in
their dust extinction down to the 10pc scale. Dust and molecular gas
are thightly coupled and therefore HST high resolution reddening maps
can reveal information about the cold ISM phase on a scale
inaccessible from the groundby any other means. We have recently
discovered a sudden change in dust lane properties using ground-based
data; all galaxies with rotation speeds in access of 120km/s show dust
lanes, but none of the slower rotators does. This transition may be
caused by a sudden change in the state of the multiphase ISM, and HST
resolution imaging is needed to fully quantify this effect. Analysis
will consist of full radiative transfer modeling of dust extinction
with realistic, fractal like substructure and power spectrum analysis
of the structure from the global to the 10pc scale. By observing a
sample of galaxies with a range in structural parameters we can
quantify how the cold ISM structure changes as function of radius,
rotation speed, local surface density, et cetera. This information is
duly needed with SIRTF soon providing a wealth of information on dust
absorption, but lacking the resolution to determine the small scale
distribution of the dust.

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. HST has demonstrated that it is the only telescope that can in
each case precisely locate the lens galaxy, measure its luminosity,
color and structure, and search for lensed images of the source host
galaxy given the typical image separations of ~1”. 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.

NIC1 9737

A NICMOS direct imaging search for giant planets around the seven
single white dwarfs in the Hyades

We propose to use the NIC1 camera on HST to search for massive giant
planets around the known seven single white dwarfs in the nearby
Hyades cluster at sub-arcsec separations. At an age of 625 Myr, the
white dwarfs had protogenitor masses of about 3 solar masses, and
massive gaseous giant planets should have formed in the massive
circumstellar disks around these ex Herbig A0 stars, probably at
orbital separations similar or slightly larger than that of Jupiter {5
AU} in our own solar system. Such planets would have survived the
post-Main Sequence mass loss of the parent star, and would have
migrated outward adiabatically by a factor 4.5, equal to the ratio of
initial to final stellar mass {3Mo/0.66Mo}, due to conservation of
orbital angular momentum during the mass loss {AGB and PN} phase. Thus
the orbital separation NOW would be 4.5 x 5 AU = 22.5 AU, which at the
distance of the Hyades {45 pc} corresponds to 0.50 arcsec. Simulations
with TinyTim then show that giant planets at this separation with
masses in the range 6-12 Jupiter masses and apparent J and H
magnitudes in the range 20.5-23.3 mag {from Baraffe or Burrows models}
can be spatially resolved around the Hyades white dwarfs. Their J and
H brightnesses are known to be 15 +/- 0.5 mag, implying a median
star-planet brightness ratio of 1000:1 {7.5 mag}. This combination of
dynamic range and orbital separation is observable with NICMOS, by
subtracting images taken at two roll angles. Therefore, the proposed
near-IR diffraction-limited observations in the F110W and F160W
filters promise to resolve giant planets around low-mass stars for the
first time. If successful, the observations would also prove that
giant planets do form around early-type stars more massive than the

WFPC2 9729

Probing the nature of Type Ia SNe through HST astrometry

Type Ia supernovae are of key importance in cosmology. Empirical
relations allow their use as cosmological standard candles. The
generally accepted picture is that the exploding star is a C+O white
dwarf which accretes matter from a companion in a binary system.
However, the nature of the companion is still unknown. It could either
be another WD, or be a giant, subgiant, or main-sequence star.
Calculations have shown that it is possible to distinguish among those
possibilities by the effect that the supernova explosion has on the
companion star. We propose to identify the companion star of the two
historical well-known SNeIa through ACS imaging of the targets
complemented by WFPC2 observations. A radial-velocity study of the
stars in those two Galactic SNeIa has been done from ground-based
facilities. To obtain the full motion vector of those stars, we plan
to use ACS for high-resolution astrometry in two different epochs.
That should allow to detect motion imparted during the explosion in
the d ir ection perpendicular to the line of sight, down to a level of
a few milliarcsecs/yr.


Towards a global understanding of accretion physics – Clues from an UV
spectroscopic survey of cataclysmic variables

Accretion inflows and outflows are fundamental phenomena in a wide
variety of astrophysical environments, such as Young Stellar Objects,
galactic binaries, and AGN. Observationally, cataclysmic variables
{CVs} are particularly well suited for the study of accretion
processes. We are currently carrying out a Cycle 11 STIS UV
spectroscopic snapshot survey of CVs to fully exploit the diagnostic
potential of these objects for our understanding of accretion physics.
While the data obtained so far are of excellent quality, the number of
targets that will be observed in Cycle 11 is too small for a
statistically significant analysis {only 19 objects out of our 149
accepted Cycle 11 snapshot targets have been observed at the time of
writing}. We propose here to extend this survey into Cycle 12,
building a homogenous database of accretion disc and wind outflow
spectra covering a wide range of mass transfer rates and binary
inclinations. We will analyze these spectra with state-of-the-art
accretion disc model spectra {SYNDISK}, testing our current knowledge
of the accretion disc structure, and, thereby, providing new insight
into the so far not well understood process of viscous dissipation. We
will use our parameterised wind model PYTHON for the analysis of the
radiation driven accretion disc wind spectra, assessing the
fundamental question whether the mass loss rate correlates with the
disc luminosity. In addition, our survey data will identify a number
of systems in which the white dwarf significantly contributes to the
UV flux, permitting an analysis of the impact of mass accretion on the
evolution of these compact stars. This survey will triple the number
of currently available high-quality accretion disc / wind outflow /
accreting white dwarf spectra, and we waive our proprietary rights to
permit a timely use of this database.

WFPC2 9709

POMS Test Proposal: WFII parallel archive proposal

This is the generic target version of the WFPC2 Archival Pure Parallel
program. The program will be used to take parallel images of random
areas of the sky, following the recommendations of the 2002 Parallels
Working Group.

ACS/WFC 9701

ACS Default {Archival} Pure Parallel Program II

The proposal is designed to test ACS pure parallels in POMS.


NICMOS Coronagraphic Performance Assessment

This test defines a coherent program designed to quantitatively
measure and map out the diffractive and scattered energy rejection of
occulted targets to improve the target/background contrast ratios by
use of the NICMOS coronagraph. The performance levels of system will
be assessed while exploring the observational parameter spaces and
execution strategies which undoubtedly will be proposed for use in HST
Cycle 11. This test is constructed in four parts with different, but
complementary, Taken together they will provide critical information
needed to re-evaluate the coronagraphic systemic performance from
which flight {and possibly ground} S/W updates, and advisories to
observers defining Phase 2 proposals will be issued.

FGS 9229

Orbits of Pre-Main Sequence Binaries

Our goal is to dynamically measure the masses of low mass pre-main
sequence stars. This is important because there are still no such
objects with an accurately measured mass. In cycle 5 we began to map
the orbits of young multiple star systems in Taurus using FGS3. In
cycle 8 we switched to the more capable FGS1r. We propose to continue
to observe these binary and triple systems so that we can establish
their visual orbits. In addition to our Transfer mode observations, we
include Position mode observations of reference field stars so that
the position of the multiple systems’ barycenter can be located,
giving the relative masses of the components. In addition, the
Position mode data will allow us to determine accurate parallaxes for
these systems, and hence the physical, absolute masses of the young
pre-main sequence stars along with absolute magnitudes.

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.

WFPC2 10082

POMS Test Proposal: WFII backup parallel archive proposal

This is a POMS test proposal designed to simulate scientific plans

WFPC2 10069

WFPC2 CYCLE 12 Supplemental Darks, Part 1/3

This dark calibration program obtains 3 dark frames every day to
provide data for monitoring and characterizing the evolution of hot

ACS/WFC 10054

ACS photometric Stability

A set of four spectrophotometric standard stars {GD71, G191B2B, GD153,
and HZ43} is observed once with ACS’s WFC and HRC through all filters,
except the ramp filters, to assess the sensitivity of the instrument
and measure accurate photometric zero points. The stars are placed at
the centre of the aperture, and two images are taken through each
filter. This programme is based on proposals 9020 and 9654 designed
for SMOV and Cycle 11, and also on programme 9563 from the interim
period. No RAMP filters are calibrated here. The exposure times have
been calculated to reach, on average, SNR~350 in the central pixel for
broad band filters.


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.

STIS/CCD 10021

CCD Read Noise Monitor

This proposal measures the read noise of all the amplifiers {A, B, C,
D} on the STIS CCD using pairs of bias frames. Full frame and binned
observations are made in both Gain 1 and Gain 4, with binning factors
of 1×1, 1×2, 2×1 and 2×2. All exposures are internals. Pairs of visits
are scheduled for bimonthly execution.

STIS/CCD 10019

CCD Bias Monitor – Part 1

Monitor the bias in the 1×1, 1×2, 2×1, and 2×2 bin settings at gain=1,
and 1×1 at gain = 4, to build up high-S/N superbiases and track the
evolution of hot columns.

STIS/CCD 10017

CCD Dark Monitor-Part 1

Monitor the darks for the STIS CCD.

STIS/CCD 10000

STIS Pure Parallel Imaging Program: Cycle 12

This is the default archival pure parallel program for STIS during cycle 12.


Significant Spacecraft Anomalies: (The following are preliminary
reports of potential non-nominal performance that will be

HSTAR 9195: GS Acquisition (1,3,1) @ 311/15:09:59Z, which began
during ZOE, resulted in FL backup on FGS 1 at AOS, without FGS
indication flags. Unable to determine FGS Modes and Flag Bit changes
pending SSR playback scheduled @ 312/05:48Z. Under investigation.

HSTAR 9198: GS Acquisition (2,1,1) @ 313/11:39:22Z resulted in FL
backup on FGS 2. No flags were triggered, but after coming out of
LOS, only FGS 2 has acquired FL. These were the same Guide Stars as
HSTAR 9185. Prior FHST Map @ 313/12:16:33Z showed errors of 0.393,
3.068, and 11.417 arcsec. Under investigation.



                            SCHEDULED     SUCCESSFUL    FAILURE TIMES
FGS GSacq                40                       40
FGS REacq                16                       16
FHST Update              58                       58


SpaceRef staff editor.