Status Report

NASA Hubble Space Telescope Daily Report # 3661

By SpaceRef Editor
July 26, 2004
Filed under , ,

HUBBLE SPACE TELESCOPE – Continuing to collect World Class Science





Ultraviolet Observations of a Very Young Brown Dwarf

We propose to obtain an ultraviolet spectrum of a 25 Jupiter mass, 10
million-year old brown dwarf in the TW Hya association. 2MASSW
J1207334-393254 shows extremely strong H alpha emission, making it the
brightest and closest member of a rare class of active young brown
dwarfs.The UV observations will characterize the hot gas that is
deduced to surround this brown dwarf. Very little about brown dwarf
activity is understood, but X-ray, optical, and radio studies have
shown that brown dwarf activity is quite different from cool star
activity. Observations are needed to understand the source of the
observed optical emission lines. The proposed observations will
supplement existing optical and scheduled Chandra X-ray data.


Recombination Lines and Temperature Structure in Planetary Nebulae

A high-spatial resolution study of recombination lines {RLs} in bright
compact planetary nebulae {PNs} is proposed. Many PNs show a large
discrepancy between abundances derived from O II RLs and those derived
from [O III]. Others show little or no discrepancy. The PNs with small
discrepancies are more compact and high surface brightness. This
program seeks to understand why PNs show such differences by studying
the RLs at high spatial resolution in the compact PNs NGC 6572 and NGC
6790, which show no discrepancy between O II and [O III], to compare
with ground-based studies of the larger PNs NGC 6153 and NGC 6720. The
goal is to determine if the distribution of RL emission in NGC 6572
and NGC 6790 is more consistent with radiative recombination than in
NGC 6720, where the RL emission is more centrally peaked than [O III].
This will allow us to demonstrate whether or not it is the RLs that
are preferentially enhanced in the nebulae with large discrepancies.
The Cat’s Eye nebula NGC 6543 will also be observed, to determine if
the enhanced RL emission is connected to the presence of X-ray
emitting gas, as might be expected if the enhanced RLs are a result of
high temperature dielectronic recombination.

NIC1 9833

T Dwarf Companions: Searching for the Coldest Brown Dwarfs

Faint companions to known stars have historically led to the discovery
of new classes of stellar and substellar objects. Because these
discoveries are typically limited by the flux ratio of the components
in the system, the intrinsically faintest companions are most
effectively identified around the intrinsically faintest primaries. We
propose to use NICMOS to image a sample of 22 of the coolest known
{T-type} brown dwarfs in the Solar Neighborhood in order to search for
fainter and cooler brown dwarf companions. The high spatial resolution
of the NIC 1 detector enables us to distinguish binary systems with
apparent separations greater than 0"08, or physical separations
greater than 1.2 AU at the nominal distances of the objects in our
sample. Furthermore, the substantial sensitivity of NICMOS imaging
allows us to probe companion masses of 5-50 Jupiter masses and
companion effective temperatures of 250-1300 K in a maximally
efficient manner. Based on work to date, we expect that roughly 20% of
the objects in our sample will be binary, and that one or two of these
will likely harbor a significantly fainter secondary. Hence, we expect
to find a companion cooler than any currently known brown dwarf, a
potential prototype for the next spectral class. In addition, our
investigation will add substantially to the sample of known binary
brown dwarfs, allowing improved statistical analyses of the binary
fraction, separation distribution, and mass ratio distribution of
these systems, key quantities for probing brown dwarf formation. We
will also identify optimal substellar systems for astrometric mass
measurements, a critical check for theoretical models of brown dwarfs
and extrasolar planets.

WFPC2 9816

Proper motion kinematics in Galactic bulge/bar fields

With this proposal we continue a successful programme to measure
proper motions in fields in the galactic bulge. We are able to reach
accuracies of ca 10km/s in transverse motion at a distance of 8kpc,
for thousands of stars per WFPC2 field. In combination with VLT
spectroscopic radial velocities and metallicity indices, we will be
able to construct a full dynamical and stellar-population model for
our Bulge. Previous fields in this programme were on the minor axis;
the fields proposed here {using first epoch observations from
1995-1998 from the archive} lie in the first quadrant, on the near
side of the Galactic bar. We also wish to establish first-epoch
observations in the 4th quadrant, where no suitable data exist so far.

ACS/HRC 9782

Measuring Black Hole Masses in Double Peaked Broad Lined AGNs

To date there have been few black hole {BH} mass estimates for
luminous broad line AGN, including those derived from reverberation
mapping. In this context, objects with "double-peaked" broad lines are
particularly important because the line emission is believed to arise
in a relativistically rotating accretion disk. If this model is
correct, then the BH mass can be determined directly from periodic
variations in the line-profile shape. In two cases {Arp 102B and NGC
1097} such variations have been claimed. The goal of this proposal is
to confront the relativistic disk model for the double-peaked Balmer
lines with independent limits on the central masses for 5 of the
nearest and brightest "double-peaked emitters" {NGC 1097, Arp 102B,
Pictor A, 3C390.3, 3C332}, determined by using STIS long-slit
spectroscopy to map the velocity field of circum-nuclear ionized gas.
These observations will critically test the idea that the line
emission in these objects comes from an accretion disk and thus
provide unique insights into the physical processes operating in both
the BLR and the "central engine".

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 9727

Exploration of the SN Ia Hubble Diagram at z > 1.2

In the spirit of a Treasury proposal, we propose to organize, and
deliver to the astronomical community, non-proprietary follow-up
observations of ~10 Type Ia supernovae at 1<z<1.7 that are expected to
be discovered in a Cycle 12 Treasury proposal. Together with the
currently available sample, this would provide a Hubble diagram with
over 20 SNe Ia in this redshift range, where it is possible to test
the current cosmological model in the epoch of deceleration: If z ~
0.5 SNe Ia are fainter due to evolution rather than an accelerating
expansion, they should continue to get fainter at even higher
redshifts. This size sample will show trends and outliers, and permit
a more rigorous treatment of the asymmetric amplification distribution
from gravitational lensing. This is a key redshift range for the
studies of dark energy that will be done with future surveys; this
dataset will lay the ground-work for these studies by establishing the
simple properties of the supernovae in this redshift range, including
magnitudes, colors, and timescales. If considered more appropriate,
this proposal could be treated as a part of a Treasury or Director’s
Discretionary program, since the data would be available to everybody
immediately, and we would welcome others who would want to work with
us on it.

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.

ACS/HRC 10330

Coronagraphic search for disks around nearby stars

We will use the coronagraphic and imaging modes of the High Resolution
camera to study of the role of circumstellar disks in planetary system
formation over timescales of ~1-1000 Myr. Our targets comprise pre
Main-Sequence {MS} and MS stars, selected by infrared excess, and
targets selected from SIRTF surveys. Some targets, like Beta Pictoris
have debris disks that have been detected at optical or near-IR
wavelengths, while others have disks inferred from mid-IR or ISO
observations. We will obtain multicolor images of each target’s
circumstellar environment for the purpose of {1} detecting and
characterizing disk morphologies over all scales {including warps and
regions of enhanced or depleted density}, and {2} seeking evidence of
embedded planets. Direct and occulted images will be recorded for
studying the disks within 2 arcseconds of these targets; the
coronagraph will be used to image the outer regions of the disks.
Together with existing infrared observations, we will provide
constraints on the sizes, distribution, and composition of dust
grains. Unconfirmed disks will first be imaged in F606W, and if they
exist we may later observe them in F435W and F814W.


SAINTS – Supernova 1987A Intensive Survey

SAINTS is a program to observe SN 1987A, the brightest supernova in
383 years, as it transforms into supernova remnant {SNR} 1987A, the
youngest supernova remnant. HST is the unique and perfect match in
scale and in field for spatially-resolved observations of SN 1987A.
Rapid changes are taking place in a violent encounter between the
fastest-moving debris and the circumstellar ring. This one-time-only
event, leading to suddenly appearing hotspots and new emission that
can reveal previously hidden gas, is powered by shocks that can be
studied simultaneously with HST and with Chandra to great advantage.
Both the optical and X-ray flux from the ring are rising rapidly so
prompt observations are needed in Cycle 13. Our previous observations
reveal a remarkable reverse shock moving upstream through the
expanding debris. The reverse shock provides a powerful tool for
dissecting the radial structure of the vanished star. The debris from
the explosion itself, still excited by radioactivity, is now well
resolved by ACS and seen to be aspherical, providing direct clues to
the mechanism of the explosion. Many questions about SN 1987A remain
unanswered. SAINTS is a comprehensive attempt to use HST to establish
the facts of SN 1987A, help to answer interesting questions, and to
observe the birth of SNR 1987A.

ACS/HRC 10255

A Never Before Explored Phase Space: Resolving Close White Dwarf / Red
Dwarf Binaries

We propose an ACS Snapshot imaging survey to resolve a well-defined
sample of highly probable white dwarf plus red dwarf close binaries.
These candidates were selected from a search for white dwarfs with
infrared excess from the 2MASS database. They represent unresolved
systems {separations less than approximately 2" in the 2MASS images}
and are distributed over the whole sky. Our HST+ACS observations will
be sensitive to a separation range {1-20 AU} never before probed by
any means. The proposed study will be the first empirical test of
binary star parameters in the post-AGB phase, and cannot be
accomplished from the ground. By resolving as few as 20 of our ~100
targets with HST, we will be able to characterize the distribution of
orbital semi-major axes and secondary star masses.

ACS/HRC 10240

Stars versus Gas: A Direct Comparison of Black Hole Mass Measurement

Hundreds of orbits of HST time have been devoted to measurements of
the masses of black holes in the centers of nearby galaxies, using the
kinematics of either stars or ionized gas disks. Gas-dynamical
measurements are far simpler in terms of observations and analysis,
but are subject to systematic uncertainties since the gas disks may
not be rotating at the local circular velocity. Cross-checks between
the two methods are critically important, but to date there has not
been any direct test of the two methods to determine whether they
would give consistent results for the same galaxy. We propose to
compare stellar-dynamical and gas-dynamical measurements of the black
hole masses in two S0 galaxies, NGC 3245 and NGC 1380, that we have
selected as excellent candidates for both techniques. This direct
comparison will help to clarify the amount of intrinsic scatter in the
black hole mass vs. stellar velocity dispersion correlation and
improve our understanding of local black hole demographics. For NGC
3245 we have already performed the gas-dynamical measurement.

NIC2 10228

Multi-color HST imaging of the GJ 803 debris disk

We propose to conduct a comprehensive high angular resolution study of
the newly discovered debris disk around GJ 803. This nearby, young
star has an estimated age of 8-20 Myr, a critical epoch in disk
evolution and planet formation. By virtue of its proximity {10 pc} and
nearly edge-on orientation, GJ 803’s disk has an exceptional surface
brightness and angular size relative to other disks resolved in
scattered light thus far. Hence, this system offers an exciting new
opportunity to study debris disks. Our proposed ACS and NICMOS imaging
will elucidate the disk morphology, ascertain the grain properties as
a function of radius, and search for fine dynamical structure
indicative of the presence of planets. ACS WFC and NICMOS
coronagraphic imaging will explore the inner disk, which includes the
~17 AU inner disk hole inferred from the star’s spectral energy
distribution. Complementary ACS WFC imaging will probe the outer disk
{>70 AU}; at such large distances around GJ 803, dust evolutionary
timescales are longer than the stellar age, and hence we can study the
composition of primordial circumstellar material. The combined dataset
will provide the most comprehensive study to date of a debris disk
from ~7 AU to ~200 AU radius.

NIC/NIC3 10226

The NICMOS Grism Parallel Survey

We propose to continue managing the NICMOS pure parallel program.
Based on our experience, we are well prepared to make optimal use of
the parallel opportunities. The improved sensitivity and efficiency of
our observations will substantially increase the number of
line-emitting galaxies detected. As our previous work has
demonstrated, the most frequently detected line is Halpha at
0.7<z<1.9, which provides an excellent measure of current star
formation rate. We will also detect star-forming and active galaxies
in other redshift ranges using other emission lines. The grism
observations will produce by far the best available Halpha luminosity
functions over the crucial–but poorly observed–redshift range where
galaxies appear to have assembled most of their stellar mass. This key
process of galaxy evolution needs to be studied with IR data; we found
that observations at shorter wavelengths appear to have missed a large
fraction of the star-formation in galaxies, due to dust reddening. We
will also obtain deep F110W and F160W images, to examine the space
densities and morphologies of faint red galaxies. In addition to
carrying out the public parallels, we will make the fully reduced and
calibrated images and spectra available on-line, with some
ground-based data for the deepest parallel fields included.

STIS/CCD 10222

The Next Generation Spectral Library

We propose to complete our 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] <
-1.5}, low {-1.5 < [Fe/H] < -0.5}, near-solar {-0.3 < [Fe/H] < 0.1},
and super-solar {[Fe/H] > 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.

ACS/WFC 10181

ACS/NICMOS Imaging of Bright Lyman Break Galaxy Candidates from SDSS

The recent surprising discovery of six unusually bright {r~20 mag}
Lyman break galaxy {LBG} candidates with z=2.45-2.80 in the Sloan
Digital Sky Survey {SDSS} raises a number of questions that only HST
can address. Specifically, what is the true nature of these objects,
and what role if any is played by gravitational lensing? We propose to
use the superior resolution and sensitivity of ACS and NICMOS to
obtain deep images of these objects and their environments. Compared
to SDSS images, HST will allow us to determine their morphologies
{extended, point-source, or lensed}, the appearance of their
environments {rich or poor}, and to detect any faint foreground groups
or clusters that might be responsible for lensing these objects. All
outcomes would be intriguing. If the objects are lensed, it increases
from 1 {MS1512-cB58} to 7 the number of normal LBGs bright enough to
study individually. If they are instead unlensed point sources, they
will represent a new class of previously unidentified absorption-line
quasars. Finally, if they are unlensed and extended star-forming
galaxies, they are at least 4mag brighter than L_* LBGs, thus making
them the most luminous star-forming objects yet seen, representing a
heretofore unknown extreme population of objects.

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.

ACS/WFC 10158

ACS Observations of the Gravitational Lens B1608+656: Characterizing
the Einstein Ring

We request time to obtain ACS deep images of the B1608+656
gravitational lens system to fully characterize its enclosing Einstein
ring with high signal-to-noise ratio {SNR}. These data will allow us
to determine the gravitational potential of the lens, locally, to
several percent accuracy and, combined with the three independent time
delays, measure H_0 to much better than 10% precision. For this goal,
we have developed powerful new lens modeling codes that make use of
the full brightness distribution of the Einstein ring in lens systems.
The B1608+656 system is ideal for our new code. It has precisely
measured time delays, a well-determined stellar velocity dispersion,
and an Einstein ring that is not dominated by the lensed nuclear
emission of the background source. When combined with high-SNR images
of Einstein rings, the new modeling codes provide qualitatively
different and much improved analysis of the ring emission than was
previously possible. The proposed ACS observations will reach the SNR
at which the new modeling code can be fully exploited {SNR=5 per
pixel}. Our simulations show that these new data will allow us to
reduce the total uncertainties in H_0 derived from the system by at
least a factor of two, to the 5-7% level for this system.

ACS/WFC 10146

Solving the problem of the White Dwarf Cooling Sequence End in M4: an
efficient approach

The end of the white dwarf {WD} cooling sequence {WDCS} has never been
observed, despite the importance that it has in providing an age
estimate of old stellar systems, independent from the standard method
of the main sequence turn off. The best targets for this investigation
are the closest stellar clusters, and, among them, globular clusters
are the most interesting ones. Being the oldest stellar aggregates,
they allow to probe the advanced WD cooling phases, and the
independent age estimate coming from the end of their WDCS has an
important cosmological impact. M4 is the best target for this
investigation. Despite huge observational efforts, we still miss the
end of its WDCS. The ACS camera offers a unique opportunity to
identify it. Coupled with already existing observations, we here prove
that we can finally reach it with only 10 HST orbits. This is probably
the last opportunity we have for a large number of years. The data we
are requesting here, will also be used to complete other two programs
of great astrophysical impact: the observational detection of the main
sequence hydrogen burning limit, and the measurement of the
geometrical distance of M4.

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


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 10020

CCD Bias Monitor – Part 2

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 10018

CCD Dark Monitor-Part 2

Monitor the darks for the STIS CCD.


Focus Monitor

The focus of HST is measured from WFPC2/PC and ACS/HRC images of
stars. Multiple exposures are taken in parallel over an orbit to
determine the influence of breathing on the derived mean focus.
Observations are taken of clusters with suitable orientations to
ensure stars appear in all fields.


Significant Spacecraft Anomalies: (The following are preliminary
reports of potential non-nominal performance that will be
investigated.) None



  • 1115-0 CCC IPCONFIG Connections @ 205/14:11z
  • 1252-0 Change Limits MAMA2 Threshold Voltage @ 205/22:10z
  • 1246-0 Battery 5 Capacity Test Ground Limits @ 206/20:11z
  • 1246-0 Battery 5 Capacity Test Ground Limits @ 206/22:11z

                        SCHEDULED     SUCCESSFUL    FAILURE TIMES
FGS GSacq            32                           32
FGS REacq            17                           17
FHST Update          49                          49


SpaceRef staff editor.