Status Report

NASA Hubble Space Telescope Daily Report # 3679

By SpaceRef Editor
August 24, 2004
Filed under , ,

HUBBLE SPACE TELESCOPE – Continuing to collect World Class Science




ACS/HRC 9862

ACS detection of sub-stellar companions around Vega, Fomalhaut and
beta Pic via parallax & proper motion

The first visible light coronagraph on HST provides contrast ratios
near very bright stars that are unparalleled by ground-based
observations. Vega, Fomalhaut and Beta Pictoris have dusty debris
disks with structure thought to originate from the presence of
yet-undetected, substellar companions. The detection of substellar
companions is possible with the ACS HRC coronagraph if observations
are made in two epochs. Here we propose to image Vega in two epochs
within Cycle 12. We argue that in a few months interval, the sky plane
motion of any companions due to parallax and proper motion is large
relative to the HRC astrometric uncertainties. Likewise, we propose to
obtain a second epoch image of Beta Pic and Fomalhaut within Cycle 12
to complement the single epoch imaging of the GTO program. Because
Vega, Fomalhaut and Beta Pictoris are young and nearby, this imaging
campaign will be sensitive to brown dwarfs and massive extrasolar
giant planets at their predicted locations 40-60 AU projected radius
from each star. Either positive or negative results for each system
will be used to constrain the physical characteristics of massive
objects hypothesized to cause the observed disk asymmetries.

NIC1/NIC2 9844

Brown dwarf atmospheric variability observations

We propose to use NIC1 and NIC2 to study brown dwarfs for atmospheric
variability. We will observe a sequence of early Ts, a detected
variable T2, a T3 and a T4.5. Atmospheric variability, that is
expected by some models for these objects, would constrain the
physical parameters of cloud vertical distribution, horizontal
homogeneity and the dynamics of the very cool atmospheres. The
existence and amplitude of the variations would reveal the size and
distribution of the cloud cover over the surface of the brown dwarf
and test a model explaining the rapidity of the L to T type
transition. The relative color changes would constrain the vertical
extent of dynamical process and the depth in the atmosphere at which
they take place. If a periodicity is measured, the rotational period
of the dwarf could be estimated. HST provides the unique and crucial
opportunity to observe beyond Earth atmospheric variable absorption,
particularly in the important water bands

NIC3 9735

ACS, NICMOS Observations of Three Ongoing Mergers

We propose to make ACS {U, B, V, I, H_alpha}, and NICMOS {J, H, K}
observations of NGC 520, NGC 2623, and NGC 3256, three merging
galaxies in the middle of the Toomre Sequence and currently in the
throes of violent relaxation. Two of these {NGC 2623 and NGC 3256} are
the most IR luminous galaxies in the sequence. Hence, these ongoing
mergers are ideal candidates for studying the triggering mechanism
responsible for the formation of stars and star clusters. The ACS
observations will allow us to age date the star clusters, and reliably
distinguish clusters from stars based on their apparent sizes. They
will also be used in conjunction with ground-based measurements of the
stellar velocity dispersion to determine dynamical masses of the
clusters and hence address the question of whether the IMF is
truncated. The NICMOS observations will allow us to penetrate the dust
and answer several fundamental questions such as: What fraction of the
young clusters are hidden by dust? How do these clusters form and

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/WFC 10325

Low Redshift Cluster Gravitational Lensing Survey

This proposal has two main scientific goals: to determine the dark
matter distribution of massive galaxy clusters, and to observe the
high redshift universe using these clusters as powerful cosmic
telescopes. Deep, g, r, i, z imaging of a sample of low-z {0.2-0.4}
clusters will yield a large sample of lensed background galaxies with
reliable photometric redshifts. By combining strong and weak lensing
constraints with the photometric redshift information it will be
possible to precisely measure the cluster dark matter distribution
with an unprecedented combination of high spatial resolution and area
coverage, avoiding many of the uncertainties which plague ground-based
studies and yielding definitive answers about the structure of massive
dark matter haloes. In addition, the cosmological parameters can be
constrained in a largely model independent way using the multiply
lensed objects due to the dependence of the Einsteining radius on the
distance to the source. We can also expect to detect several highly
magnified dropout galaxies behind the clusters in the redshift ranges
4-5 5-6 and 7-8, corresponding to a drop in the flux in the g, r, and
i bands relative to longer wavelength. We will obtain the best
information to date on the giant arcs already known in these clusters,
making possible detailed, pixel-by-pixel studies of their star
formation rate, dust distribution and structural components, including
spiral arms, out to a redshift of around z~2.5 in several passbands.


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.

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.

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.

ACS/WFC 10216

Co-evolution of spheroids and black holes

The masses of the giant black holes in galaxies are correlated with
the luminosities, masses, and velocity dispersions of their host
spheroids. This empirical connection of phenomena on widely different
scales {from sub-parsec to kiloparsec} suggests that the evolution of
a galaxy and its central black hole are closely linked. We propose to
test various unified formation models, by measuring the cosmic
evolution of the black hole/spheroid relations, back to z=0.37 {a
lookback time of 4 Gyrs}. We will obtain 1-orbit ACS images of a
sample of 20 Seyfert 1 galaxies, for which we already have extensive
new ground-based measures of the black hole masses and the stellar
velocity dispersions. HST resolution is required for accurate
measurement of the nonstellar AGN continuum, and the luminosity and
effective radius of the bulge of each host galaxy. This will complete
the set of observables needed to map the co-evolution of spheroids and
black-holes. The proposed sample is the minimum required to make the
first measure of the black hole mass/bulge correlation and of the
fundamental plane for active galaxies outside the local Universe.

ACS/WFC 10210

Groups of Dwarf Galaxies: Pools of Mostly Dark Matter?

Within 5 Mpc, there are 6 groups with well-known luminous galaxies but
there also appears to be a comparable number of groups containing only
dwarfs. If these dwarf entities are truly bound then M/L values are an
order of magnitude higher than values found for groups with luminous
spiral galaxies. There are theoretical reasons to anticipate that low
mass halos may frequently be mostly dark. The dynamical influence of
low mass halos is negligible in familiar groups with luminous members.
By contrast, a study of the dynamics of `groups of dwarfs’ may provide
direct evidence of the existence of dark matter potential wells with
few baryons. The goal of the present study is to gather detailed
information on the 3-D distribution of dwarf galaxies suspected to lie
within 7 groups of dwarfs within 5 Mpc. Distances with 7% relative
accuracy can be measured with the Tip of the Giant Branch method with
ACS and integrations within 1 orbit per target.

ACS/WFC 10207

Star Formation in Damped Lya Galaxies: Testing the Connection with the
Lyman Break Population

The principal challenge of damped Lya {DLA} research is to identify
and study the stellar components of these galaxies. Although two
decades of absorption-line research has yielded the HI gas content,
metallicity, velocity fields, molecular and dust content of these
galaxies only a handful have been studied in emission. Therefore, it
has been very difficult to compare the DLA galaxies with the
successful surveys of high z galaxies discovered in emission {e.g.
Lyman break galaxies; LBG}. This is particularly important given that
DLA systems are the probable precursors to galaxies like the Milky
Way. Because the DLA systems are identified toward bright background
quasars, deep observations at high spatial resolution with astable PSF
are essential. Recently, two major advances have greatly enhanced the
prospects for measuring emission from DLA host galaxies: {1} we have
developed a new spectroscopic technique for inferring the star
formation rates {SFR} of the DLA which enables one to pre-select the
brightest candidates; {2} the high spatial resolution and sensitivity
of the ACS represents a major improvement over previous capabilities.
We will obtain deep V-band images with the ACS of 5 high z DLA with
the highest inferred apparent optical magnitudes. The complete survey
will offer a robust statistical analysis of: {a} the extent and
morphology of the DLA star forming regions; {b} the likelihood that
the DLA and LBG correspond to the same population of protogalaxies;
{c} a test of the protogalactic clump models favored by CDM cosmology.
We emphasize this program will offer a major advance over all previous
studies. Finally, we will complement these HST observations with an
extensive observing campaign {IFU spectroscopy and deep IR imaging} on
the Keck, VLT, and Magellan telescopes to provide the most extensive
dataset yet on the physical properties of high z DLA.

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 attempts 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.

ACS/HRC 10182

Towards a Comprehensive Understanding of Type Ia Supernovae: The
Necessity of UV Observations

Type Ia supernovae {SNe Ia} are very important to many diverse areas
of astrophysics, from the chemical evolution of galaxies to
observational cosmology which led to the discovery of dark energy and
the accelerating Universe. However, the utility of SNe Ia as
cosmological probes depends on the degree of our understanding of SN
Ia physics, and various systematic effects such as cosmic chemical
evolution. At present, the progenitors of SNe Ia and the exact
explosion mechanisms are still poorly understood, as are evolutionary
effects on SN Ia peak luminosities. Since early-time UV spectra and
light curves of nearby SNe Ia can directly address these questions, we
propose an approach consisting of two observational components: {1}
Detailed studies of two very bright, young, nearby SNe Ia with HST UV
spectroscopy at 13 epochs within the first 1.5 months after discovery;
and {2} studies of correlations with luminosity for five somewhat more
distant Hubble-flow SNe Ia, for which relative luminosities can be
determined with precision, using 8 epochs of HST UV spectroscopy
and/or broad-band imaging. The HST data, along with extensive
ground-based optical to near-IR observations, will be analyzed with
state-of-the-art models to probe SN Ia explosion physics and constrain
the nature of the progenitors. The results will form the basis for the
next phase of precision cosmology measurements using SNe Ia, allowing
us to more fully capitalize on the substantial past {and future}
investments of time made with HST in observations of high-redshift SNe

ACS/WFC 10178

Imaging Polarimetry of Young Stellar Objects with ACS and NICMOS: A
study in dust grain evolution

The formation of planetary systems is intimately linked to the dust
population in circumstellar disks, thus understanding dust grain
evolution is essential to advancing our understanding of how planets
form. By combining {1} the high resolution polarimetric capabilities
of ACS and NICMOS, {2} powerful 3-D radiative transfer codes, and {3}
observations of objects known to span the earliest stellar
evolutionary phases, we will gain crucial insight into the initial
phases of dust grain growth: evolution away from an ISM distribution.
Fractional polarization is a strong function of wavelength, therefore
by comparing polarimetric images in the optical and infrared, we can
sensitively constrain not only the geometry and optical depth of the
scattering medium, but also the grain size distribution. By observing
objects representative of the earliest evolutionary sequence of YSOs,
we will be able to investigate how the dust population evolves in size
and distribution during the crucial transition from a disk+envelope
system to a disk+star system. The proposed study will help to
establish the fundamental time scales for the initial depletion of
ISM-like grains: the first step in understanding the transformation
from small submicron sized dust grains, to large millimeter sized
grains, and untimely to planetary bodies.


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/HRC 10102

Rings of Uranus: Dynamics, Particle Properties and Shepherding Moons

Last year, our Uranian ring and moon observing program {GO-9823}
resulted in the discovery of two moons, S/2003 U 1 and S/2003 U 2. We
imaged two additional small moons, Ophelia and S/1986 U 10, that had
not been seen since the Voyager encounter of 1986. Furthermore, our
data show faint arcs and clumps orbiting within the rings, which were
not seen by Voyager and are completely unexpected. We employed several
"tricks" of the HRC to achieve this remarkable sensitivity;
specifically, we used the CLEAR filter and oriented the images so that
the planet, though vastly overexposed, did not interfere with the
ring/moon region of interest to us. This allowed us to detect
25th-magnitude moons circling a 5th-magnitude planet. Now we propose
to complete the task by carrying out a comprehensive survey of the
system using the same techniques. Our goals are to recover the moons,
better discern their orbital elements, and learn more about the
dynamics of the ring clumps. In particular, we need to {1} understand
the long-term stability of S/2003 U 2, which orbits perilously close
to the larger moon Belinda; {2} complete our search for moons, which
was only ~ 50% complete last year, and {3} better understand how the
clumps and arcs within the ring system might relate to nearby
"shepherding" moons, seen or unseen. This program is now a merger of
two programs 10275 and 10102. The former is our new program, whereas
the latter is the second year of our three-year program to study the
light scattering properties of Uranus’s rings as they approach their
edge-on presentation in 2007.

WFPC2 10080

Wavelength Stability of Narrow Band and Linear Ramp Filters

Verify the mapping of wavelength as a function of CCD position on
LRFs; check for changes in central wavelengths of narrow band filters.

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.

ACS/HRC 10050

ACS Earth Flats

High signal sky flats will be obtained by observing the bright Earth
with the HRC and WFC. These observations will be used to verify the
accuracy of the flats currently used by the pipeline and will provide
a comparison with flats derived via other techniques: L-flats from
stellar observations, sky flats from stacked GO observations, and
internal flats using the calibration lamps. Weekly coronographic
monitoring is required to assess the changing position of the spots.


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.)

HSTAR 9521: GS Acquisition (2,3,2) @ 234/14:38:53Z resulted in FL
backup (2,0,2) due to SSLE on FGS 3. Under investigation.


1115-0 CCC IPCONFIG Connections @ 233/10:52z

                          SCHEDULED     SUCCESSFUL    FAILURE TIMES
FGS GSacq              28                       28
FGS REacq              22                        22
FHST Update            44                        44


Battery 3 Capacity Test is scheduled to start on entry into shadow @
236/12:34Z (OR 17259 with attached script). Solar Arrays are being
managed to be near normal during the period 236/11:40Z – 239/07:00Z.
Continuous Engineering Recording (CER) is scheduled to occur
236/12:34Z – 20:34Z.

SpaceRef staff editor.