Status Report

HST Daily Report # 3302 Part 2

By SpaceRef Editor

February 21, 2003

Filed under Hubble Space Telescope, Space Telescope Science Institute, US

NICMOS 9485

Completing A Near-Infrared Search for Very Low Mass Companions to Stars
within
10 pc of the Sun

Most stars are fainter and less massive than the Sun. Nevertheless, our
knowledge of very low mass {VLM} red dwarfs and their brown dwarf cousins
is
quite limited. Unknown are the true luminosity function {LF},
multiplicity
fraction, mass function, and mass-luminosity relation for red and brown
dwarfs,
though they dominate the Galaxy in both numbers and total mass. The best
way to
constrain these relations is a search for faint companions to nearby
stars.
Such
a search has several advantages over field surveys, including greater
sensitivity to VLM objects and the availability of precise parallaxes
from
which
luminosities and masses can be derived. We propose to complete our
four-filter
NICMOS snapshot search for companions to stars within 10 pc. With a 10
sigma
detection limit of M_J ~ 20 at 10 pc, we can detect companions between 10
and
100 AU that are at least 9 mag fainter than the empirical end of the main
sequence and at least 6.5 mag fainter than the brown dwarf Gl 229B. When
completed, our search will be the largest, most sensitive, volume-limited
search
for VLM companions ever undertaken. Our four-filter search will permit
unambiguous identification of VLM-companion candidates for follow-up
observation. Together with IR speckle and deep imaging surveys, our
program
will
firmly establish the LF for VLM companions at separations of 1-1000 AU
and the
multiplicity fraction of all stars within 10 pc.

NICMOS 9386

Infrared Photometry of a Statistically Significant Sample of KBOs

While the discovery rate of Kuiper Belt objects is accelerating, the
physical
study of this new region of the solar system has been slowed by a lack of
basic
astrophysical data. Photometric observations of the majority of the more
than
400 known KBOs and Centaurs are rudimentary and incomplete, particularly
in the
infrared. The multicolor optical-infrared photometry that exists for a
small
subset of KBOs often shows significant discrepancies between observations
by
different observers. Their intrinsic faintness puts them at the practical
limits
of ground-based systems. In July 2001 we began what will be the largest
uniform
sample of optical photometry of KBOs with a WFPC2 SNAPSHOT program that
will
perform accurate photometry at V, R, and I on a sample of up to 150
targets. We
seek to greatly enhance the value of this survey by obtaining J and H
photometry
on the same sample using NICMOS. Combined optical and infrared broad band
photometry is a far more powerful tool for physical studies than is
either
alone. Our sample includes objects that will be observed at thermal
infrared
wavelengths by SIRTF and will be used with those data to derive the first
accurate diameters, albedos, and surface properties for a large sample of
KBOs.

NICMOS 8790

NICMOS Post-SAA calibration – CR Persistence Part 1.

NICMOS 8791

NICMOS Post-SAA calibration – CR Persistence Part 2

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.

NICMOS 9360

Paschen-alpha Imaging of a SIRTF-Selected Nearby Galaxy Sample

We propose to carry out a NICMOS snapshot survey in the Paschen-alpha
{PAlpha}
emission line and H-band of the sample of galaxies being observed at 3.5
— 160
microns as part of SIRTF Nearby Galaxies Survey {SINGS} and a related
guaranteed
time survey of starburst galaxies. The PAlpha images, accessible only
from HST,
will be combined with groundbased HAlpha imaging to measure the
extinction in
the star-forming centers of these galaxies, and obtain robust,
extinction-
corrected maps of the massive star formation rate {SFR}. The PAlpha data
by
themselves will provide reliable `extinction- free’ SFRs, and a
cross-calibration of the {dust–affected} HAlpha– and UV–based SFRs.
The
PAlpha–based SFR measurements will extend the SFR-vs.-gas density law
{Schmidt–law} to surface densities at least 30 times higher than what is
accessible using HAlpha–based SFR measurements alone, bridging the gap
between
normal galaxies and IR–luminous starbursts. Furthermore, the combination
of the
HST PAlpha images with the SIRTF images and spectra, as well as ancillary
ground–based UBVRIJHK images and GALEX UV images being obtained as part
of the
SINGS project, will provide a definitive study of the radiative transfer
of
starlight and dust heating in star–forming galaxies. The processed
NICMOS
images will be incorporated into the public SINGS Legacy Data Archive, to
enable
scores of follow-up studies by the astronomical community at large.

NICMOS 9639

Photometric Stability

This NICMOS calibration proposal carries out photometric monitoring
observations
during cycle 11.

NICMOS 9414

Resolved halo stellar populations in the Milky Way analogue edge-on
galaxy NGC
891

The stellar halo is one of the fundamental building blocks of galaxies.
Although
ground-based surface photometry has shown that stellar halos exist in
some
spiral galaxies, with colours similar to those of the main disk, little
else is
known about their stellar populations. We propose to carry out a
systematic
study of the halo regions of the edge-on galaxy NGC 891. The resulting
deep
colour-magnitude diagrams will be used to infer the mean metallicity of
the
bright halo giants at the tip of the RGB and below, and its metallicity
spread.
Recently, Zepf et al. {2000} inferred that the halo metallicity of NGC
5907 has
to be low {Fe/H <= -1.7}, with a large stellar M/L ratio. We will be able
to
test this hypothesis with much better and deeper data. If we can confirm
a
similar halo composition in NGC 891, this would imply that the Milky Way
halo
might be very different from external halos. Since galactic halos trace
the
history of galaxy formation, this will have important implications for
our
understanding of galactic evolution on cosmological time scales. Using
these
survey data, we will be able to conclusively distinguish between genuine
halo
objects and merger remnants, without having to assume a scenario in which
the
halo field population is fully mixed. Surprisingly, such studies have not
yet
been undertaken for NGC 891, although the galaxy is a prime Milky Way
analogue.

NICMOS 9484

The NICMOS Parallel Observing Program

We propose to manage the default set of pure parallels with NICMOS. Our
experience with both our GO NICMOS parallel program and the public
parallel
NICMOS programs in cycle 7 prepared us to make optimal use of the
parallel
opportunities. The NICMOS G141 grism remains the most powerful survey
tool for
HAlpha emission-line galaxies at cosmologically interesting redshifts. It
is
particularly well suited to addressing two key uncertainties regarding
the
global history of star formation: the peak rate of star formation in the
relatively unexplored but critical 1<= z <= 2 epoch, and the amount of
star
formation missing from UV continuum-based estimates due to high
extinction. Our
proposed deep G141 exposures will increase the sample of known HAlpha
emission-
line objects at z ~ 1.3 by roughly an order of magnitude. We will also
obtain a
mix of F110W and F160W images along random sight-lines to examine the
space
density and morphologies of the reddest galaxies. The nature of the
extremely
red galaxies remains unclear and our program of imaging and grism
spectroscopy
provides unique information regarding both the incidence of obscured star
bursts and the build up of stellar
mass at intermediate redshifts. In addition to carrying out the parallel
program
we will populate a public database with calibrated spectra and images,
and
provide limited ground- based optical and near-IR data for the deepest
parallel
fields.

NICMOS 9680

The X-Ray Emission Mechanism from Optical Jets: 3C 78

Radio to X-ray spectral coverage and sub-arcsec imaging provide powerful
diagnostics of the electron energy distribution and electron acceleration
in
jets. 3C 78 is the longest optical jet not to have been adequately
observed
with
Chandra, although it is one of only three jets with HST polarimetry. Our
5-ks
exploratory ACIS-S3 observation of 3C 78 in A0-3 demonstrated that the
jet is
detectable in the X-ray, lying outside the PRF of the core and above any
diffuse
emission from the host galaxy. Here we request a 55 ks ACIS-S observation
to
complete X-ray work on this jet, and two HST NICMOS near-IR exposures.
These
data will investigate electron acceleration mechanisms both in the
diffuse
regions of the jet and in the anomalous x-ray/optical knot 1.5 arcsec
from the
core.

NICMOS/STIS CCD 9405

The Origin of Gamma-Ray Bursts

The rapid and accurate localization of gamma-ray bursts {GRBs} promised
by a
working HETE-2 during the coming year may well revolutionize our ability
to
study these enigmatic, highly luminous transients. We propose a program
of HST
and Chandra observations to capitalize on this extraordinary opportunity.
We
will perform some of the most stringent tests yet of the standard model,
in
which GRBs represent collimated relativistic outflows from collapsing
massive
stars. NICMOS imaging and STIS CCD spectroscopy will detect broad atomic
features of supernovae underlying GRB optical transients, at luminosities
more
than three times fainter than SN 1998bw. UV, optical, and X-ray
spectroscopy
will be used to study the local ISM around the GRB. Chandra spectroscopy
will
investigate whether the GRB X-ray lines are from metals freshly ripped
from the
stellar core by the GRB. HST and CTIO infra-red imaging of the GRBs and
their
hosts will be used to determine whether `dark’ bursts are the product of
unusually strong local extinction; imaging studies may for the first time
locate
the hosts of `short’ GRBs. Our early polarimetry and late-time broadband
imaging
will further test physical models of the relativistic blast wave that
produces
the bright GRB afterglow, and will provide unique insight into the
influence of
the GRB environment on the afterglow.

STIS 9607

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 9605

CCD Dark Monitor-Part 1

Monitor the darks for the STIS CCD

STIS 9509

Probing the Distance and Structure of the LMC Using Eclipsing Binaries:
STIS

The distance to the LMC is crucial to calibrating the Cosmic Distance
Scale but
remains controversial and uncertain despite the efforts of many
investigators.
We have shown that the analysis of eclipsing binary {EB} systems has the
potential to resolve this controversy. We have determined accurate
distances to
three eclipsing binaries in the LMC. Two EBs in the LMC bar, HV 2274 and
EROS
1044, yield a consistent distance of 46.0+/-1.2 kpc for the bar itself. A
third
system, HV 982, is located at a greater distance {50.2+/-1.2 kpc}, which
is
similar to that of the nearby SN 1987A {51.4+/-1.2 kpc}. These results
may
suggest a significant depth to the LMC populations but a larger stellar
sample
is needed to verify this. The distances of the program stars were derived
from
ground-based light curves, HST or CTIO radial velocity data, and HST
UV/optical
spectrophotometry. We propose HST/STIS low-resolution spectra of seven
LMC EBs
for which we already have radial velocity and light curves. This will
permit us
to complete the analysis and derive accurate {to ~3%} individual
distances.
HST/STIS spectroscopy {covering 115-800nm} is a key dataset because it
provides
Teff, Fe/H, and A_lambda. The ensemble of targets, in addition to nailing
down
the distance to the LMC, will provide fundamental stellar properties and
a
detailed probe of the structure and spatial extent of this important
galaxy, in
particular its line-of-sight depth.

STIS 9614

STIS CCD Imaging Flats C11

Investigate flat-field stability over a monthly period.

STIS 9613

STIS CCD Spectroscopic Flats C11

Obtain CCD flats on the STIS CCD in spectroscopic mode.

STIS 9624

STIS FUV-MAMA Cycle 11 Flats

This program will obtain FUV-MAMA observations of the STIS internal
Krypton
lamp
to construct an FUV flat applicable to all FUV modes

STIS 9625

STIS NUV-MAMA Cycle 11 Flats

This program will obtain NUV-MAMA observations of the STIS internal
Deuterium
lamp to construct an NUV flat applicable to all NUV modes

STIS 9633

STIS parallel archive proposal – Nearby Galaxies – Imaging and
Spectroscopy

Using parallel opportunities with STIS which were not allocated by the
TAC, we
propose to obtain deep STIS imagery with both the Clear {50CCD} and
Long-Pass
{F28X50LP} filters in order to make color-magnitude diagrams and
luminosity
functions for nearby galaxies. For local group galaxies, we also include
G750L
slitless spectroscopy to search for e.g., Carbon stars, late M giants and
S-type
stars. This survey will be useful to study the star formation histories,
chemical evolution, and distances to these galaxies. These data will be
placed
immediately into the Hubble Data Archive.

STIS 9706

STIS Pure Parallel Imaging Program: Cycle 10

This is the default archival pure parallel program for STIS during cycle
10.

STIS 9398

Understanding Irradiation and Dipping Behaviour in Low Mass X-ray
Binaries

It is now clear that X-ray irradiation is the driving force behind many
of the
observed properties of accretion discs on a huge range of scales from
Galactic
interacting binaries to AGN. However to study the detailed physics of
this
process requires the accessible timescales and geometrical constraints
afforded
by Galactic low mass X-ray binaries {LMXBs}. The ideal object for this
study is
EXO 0748-676 {UY Vol} because of its high inclination and full spectrum
of LMXB
phenomenology: type I bursts, dips and total eclipses. It is also
remarkable as
it was designated a transient on its discovery in 1985, but remains X-ray
active
to this day, thereby providing a potential unifying link between
persistent and
transient systems. Its present high state is likely maintained by X-ray
heating;
hence we can learn about a disk strongly influenced by irradiation. STIS
TIMETAG
observations in the far-UV will eclipse map continuum and emission lines;
examine obscuration by the likely thick disk rim; and search for the UV
signatures of dips and bursts. This provides an unprecedented range of
techniques with which to probe the structure of an irradiated accretion
disk and
further our understanding of the irradiation of accretion flows in
general.

STIS 9487

UV Sounding of the M-Giant Atmosphere in the Symbiotic Binary EG-AND

EG-AND is an eclipsing system which provides us with the capability to
study the
structure of a fairly normal non- variable red giant point-by-point
through its
atmosphere. The white dwarf secondary provides a bright far-UV continuum
source
against which absorption from a broad range of ionization levels can be
seen,
ranging from molecular hydrogen close to the giant star to ionized
material
further away. The systemic velocity is such that these features are well
resolved from the intervening ISM component. In addition, the system has
low
extinction {A_V = 0.15}, has never been observed to undergo an eruption,
and has
a circular orbit, so there is no periodic disturbance of the giant
atmosphere.
Both calculation and direct observation show that the effect of the dwarf
star’s
ionizing continuum on the red giant is minimal. We have an on-going FUSE
program
that has covered part of the orbital cycle. We have proposed for FUSE
Cycle 3,
and we request observing time with STIS to complete the picture. The
resolution
of the FUSE and STIS spectra are well-matched and suitable for detailed
comparison of the intrinsic atmospheric features. Existing archival IUE
data is
insufficient for our purposes due to low resolution and/or low S/N. HRS
data is
of low S/N, partial wavelength coverage, and may suffer from instrumental
scattered light. Even when both datasets are combined, some phases have
never
been observed in the UV.

STIS 9441

Zinc Abundances in Damped Ly-Alpha Systems at z < 0.5: A Missing Link in
the
Chemical History of Galaxies

The evolution of metallicity in damped Lyman alpha {DLA} quasar
absorption
systems is an important constraint on the global star formation history
of the
universe, but remains a big puzzle at present. The H I column density
weighted
mean metallicity in DLAs is expected to rise to solar values at low
redshifts,
based on cosmic chemical evolution models, because the mass-weighted mean
metallicity of local galaxies is near- solar. However, current DLA
abundance
studies are highly uncertain and cannot distinguish between evolution and
no
evolution in the mean metallicity at redshifts 0.4 < z < 3.5. The
existing data
are particularly incomplete because no Zn measurements exist for z < 0.4,
and
only 2 exist for z < 0.5, which spans the past 35-45 % of the age of the
universe. To pin down the cosmic age-metallicity relation all the way to
the
present epoch, we propose to measure Zn abundances in five DLAs at 0.1 <
z <
0.5. We propose to use HST STIS because it is the only existing
instrument that
can measure the necessary UV lines. Our observations will clearly
distinguish
between no metallicity evolution vs. the predicted evolution. Our data
will
also
provide Cr measurements, which will help to estimate the dust abundance.
The
proposed observations are crucial for tying together the absorption and
emission
histories of gas and stars in galaxies and for clarifying the relation of
DLAs
to present-day galaxies.

STIS/CAL 9609

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 monthly
execution.

STIS/CCD 9066

Closing in on the Hydrogen Reionization Edge of the Universe.

The Space Telescope Imaging Spectrograph (CCD) was used in parallel
constrain
the Hydrogen reionization edge in emission that marks the transition from
a
neutral to a fully ionized IGM at a predicted redshifts.

STIS/CCD 9164

Helical Flows and Rotation in Protostellar Jets.

The Space Telescope Imaging Spectrograph (CCD) was used to study the
velocity
structure of protostellar jets transverse to the jet flow axis. HST
resolution
would allow the search for rotation, e.g. a helical flow pattern, around
the
axis of an optical jet. Such a detection would provide strong evidence
that
jets
act as outflowing channels for angular momentum, thus allowing infalling
material to fully accrete onto the protostar.

STIS/CCD/MA1 9357

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 propose to carry out a
STIS UV
spectroscopic snapshot survey of CVs that fully exploits the diagnostic
potential of these objects for our understanding of accretion physics.
This
survey will provide an homogenous database of accretion disc and wind
outflow
spectra covering a wide range of mass transfer rates and binary
inclinations. We
will analyse 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 at least double, if not triple, the number of
high-quality accretion disc / wind outflow / accreting white dwarf
spectra, and
we waive our proprietary rights to permit a timely use of this database.

STIS/FUV 9412

The Physical Parameters of the Hottest, Most Luminous Stars as a Function
of
Metallicity

We have obtained excellent, new ground-based blue optical and HAlpha
spectra of
a sample of very early-type stars in the Magellanic Clouds in order to
measure
their physical properties, for comparison with the extensive data that
exists
for higher-metallicity Galactic stars. Our aim is to understand how
effective
temperatures depend upon metallicity {necessary in determining IMFs}, and
to
explore the astrophysically interesting regime of stars of extreme
temperatures,
masses, and luminosities. In order to do this, we need to measure the
stellar
wind terminal velocities for our stars, necessary to constrain the
stellar
models. These can only be measured with STIS/FUV on HST. In addition, we
will
obtain higher spatial resolution data on the HAlpha line for stars for
which
nebular contamination is significant in our ground-based data. We also
include
several R136 stars with excellent STIS/CCD data but which lack UV line
measures.
These new HST data will provide important information about the strengths
of
stellar winds at extreme luminosities and the calibration of the Wind
Momentum-
Luminosity Relationship at lower metallicities. This proposal was highly
rated
in Cycle 9, but only 4 snapshots were obtained. We have completed the
analysis
of these plus additional data from the archives, but need spectra of the
remaining objects if we are to answer the questions we pose.

WFPC2 9699

POMS Test Proposal: WFII backup parallel archive proposal

This is a POMS test proposal designed to simulate scientific plans.

WFPC2 9676

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.

WFPC2 9634

POMS Test Proposal: WFII targeted parallel archive proposal

The parallel opportunities available with WFPC2 in the neighborhood of
bright
galaxies are treated in a slightly different way from the normal pure
parallels.
Local Group galaxies offer the opportunity for a closer look at young
stellar
populations. Narrow-band images in F656N can be used both to identify
young
stars via their emission lines, and to map the gas distribution in
star-forming
regions. Thus, the filter F656N is added to the four standard filters.
Near
more
distant galaxies, up to about 10 Mpc, we can map the population of
globular
clusters; for this purpose, F300W is less useful, and only F450W, F606W,
and
F814W will be used.

WFPC2 9596

WFPC2 CYCLE 11 INTERNAL MONITOR

This calibration proposal is the Cycle 11 routine internal monitor for
WFPC2, to
be run weekly to monitor the health of the cameras. A variety of internal
exposures are obtained in order to provide a monitor of the integrity of
the CCD
camera electronics in both bays {gain 7 and gain 15}, a test for quantum
efficiency in the CCDs, and a monitor for possible buildup of
contaminants on
the CCD windows.

WFPC2 9592

WFPC2 CYCLE 11 Standard Darks

This dark calibration program obtains dark frames every week in order to
provide
data for the ongoing calibration of the CCD dark current rate, and to
monitor
and characterize the evolution of hot pixels. Over an extended period
these
data
will also provide a monitor of radiation damage to the CCDs.

WFPC2 9594

WFPC2 CYCLE 11 SUPPLEMENTAL DARKS pt2/3

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

WFPC2 9599

WFPC2 Cycle 11 UV Earth Flats

Monitor flat field stability. This proposal obtains sequences of earth
streak
flats to improve the quality of pipeline flat fields for the WFPC2 UV
filter
set. These Earth flats will complement the UV earth flat data obtained
during
cycles 8-10.

WFPC2 9589

WFPC2 Decontaminations and Associated Observations Pt. 1/3

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.

SpaceRef Editor

SpaceRef staff editor.

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