NASA Hubble Space Telescope Daily Report # 3451 (part 1)

HUBBLE SPACE TELESCOPE

DAILY REPORT # 3451

PERIOD COVERED: DOYs 261-264

OBSERVATIONS SCHEDULED

ACS 9984

Cosmic Shear With ACS Pure Parallels

Small distortions in the shapes of background galaxies by foreground
mass provide a powerful method of directly measuring the amount and
distribution of dark matter. Several groups have recently detected
this weak lensing by large-scale structure, also called cosmic shear.
The high resolution and sensitivity of HST/ACS provide a unique
opportunity to measure cosmic shear accurately on small scales. Using
260 parallel orbits in Sloan textiti {F775W} we will measure for the
first time: beginlistosetlength sep0cm setlengthemsep0cm setlength
opsep0cm em the cosmic shear variance on scales <0.7 arcmin, em the skewness of the shear distribution, and em the magnification effect. endlist Our measurements will determine the amplitude of the mass power spectrum sigma_8Omega_m^0.5, with signal-to-noise {s/n} ~ 20, and the mass density Omega_m with s/n=4. They will be done at small angular scales where non-linear effects dominate the power spectrum, providing a test of the gravitational instability paradigm for structure formation. Measurements on these scales are not possible from the ground, because of the systematic effects induced by PSF smearing from seeing. Having many independent lines of sight reduces the uncertainty due to cosmic variance, making parallel observations ideal.

ACS/HRC 9976

The Parallaxes and Proper Motions of Two Nearby Neutron Stars

We propose to measure the parallax of two nearby neutron stars to the
highest possible level of accuracy, ~.0.5 mas. The primary goal is to
determine the neutron-star radius at infinity with better than 1 km
precision, and therewith obtain a direct constraint on the equation of
state of matter at supra-nuclear density. The required flux and
temperature determinations are easiest for the so-called isolated or
radio-quiet neutron stars because of their apparently completely
thermal spectrum. We argue that the importance of the possible results
warrants a study to the best possible level of the best possible
sources, and request 24 orbits for the two brightest isolated neutron
stars, RX J1856.5-3754 and RX J0720.4-3125. We will also determine
whether the enigmatic RX J0720.4-3125 is an old magnetar or an
accreting source, based on its luminosity and proper motion.

STIS/ACS/HRC 9975

Ozone, Condensates, and Dust in the Martian Atmosphere

We propose to utilize the unique UV capabilities of STIS and ACS/HRC
in order to study the spatial and seasonal variations in ozone,
condensates, and dust in the Martian atmosphere. The data obtained
will be critical in addressing recent breakthroughs in understanding
the basic radiative, transport, and microphysical processes that
provide for both long-term and short-term balance within the global
Mars climate system. The proposal includes both Cycle 11 & 12
observations in order to span the classic dust storm season on Mars
and provide the first good opportunity for HST to observe a dusty
atmosphere on the planet. The UV observations will complement visible
and IR observations that will be made during the Mars Global Surveyor
Extended Mission and will provide support for the future UV
observations of MARCI on the 2005 Mars Reconnaissance Orbiter.

STIS 9973

Intensive Coverage of the Eta Carinae Event in 2003

For a variety of reasons, HST can provide a very special and unique
data set when Eta Car experiences its next spectroscopic event in
mid-2003. Explaining the phenomenon is only part of the motivation.
This star and its ejecta have unique characteristics that make them
important for several branches of astrophysics; and when a
spectroscopic event occurs, it’s like varying the parameters in an
experiment {or rather, set of experiments}. The 2003 event may be the
only chance in the forseeable future to obtain such a data set,
especially with HST. Eta Carinae has extreme parameters; it is
mysterious in surprisingly basic ways; and HST/STIS can gather useful
data on it at a terrific rate. As we explain below, the proposed data
set will be valuable in several independent ways: It will help solve a
specific set of current problems, it will constitute a large and
unique archival data base for both stellar and nebular astrophysics,
and it will be well-suited for educational uses.

FGS 9969

FGS Astrometry of the Extrasolar Planet of Epsilon Eridani

We propose observations with HST/FGS in Position Mode to determine the
astrometric elements {perturbation orbit semimajor axis and
inclination} of the candidate extra-solar planet around the K2 V star
Epsilon Eridani that has been detected by Doppler spectroscopy. These
observations will also permit us to determine the actual mass of the
planet by providing the sin{i} factor which can not be determined with
the radial velocity method. High precision radial velocity {RV}
measurements spanning the years 1980.8–2000.0 for the nearby {3.22
pc} star Epsilon Eri show convincing variations with a period of ~ 7
yrs. These data represent a combination of six independent data sets
taken with four different telescopes. A least squares orbital solution
using robust estimation yields orbital parameters of period, P = 6.9
yrs, velocity K- amplitude = 19 m/s, eccentricity e = 0.6, projected
companion mass M_B sin{i} = 0.83 M_Jupiter. An estimate of the
inclination yields a perturbation semi-major axis, Alpha = 0arcs0022,
easily within the reach of HST/FGS astrometry.

ACS/WFC/HRC 9895

The Role of Groups in the Evolution of Galaxies at Intermediate Redshifts

Groups are the most common environment experienced by galaxies, yet
they remain the least studied. The tidal fields and dynamical friction
encountered by galaxies in groups probably holds the key to
understanding the role of environment in driving the evolution of
galaxies since z ~ 1. To study the evolution of galaxies in the group
environment, we propose the first unbiased HST study of groups at
moderate redshifts. Unlike previous HST group samples, that relied on
radio or X-ray properties, our kinematically selected sample is drawn
from a large redshift survey and is not biased towards unusually dense
groups. HST imaging is essential to determine the morphology of
galaxies in these systems and contrast this with the properties of
galaxies in denser and more evolved groups and rich clusters at these
epochs. HST data are also required to adequately compare the
properties of groups at intermediate redshifts with local group
samples derived from the 2df and Sloan surveys. We will combine the
HST images with deep ground-based observations to study how
morphologies and stellar populations of galaxies in groups have
evolved in time. These observations are key to understanding the
decline in the volume averaged star formation rate in the universe.

STIS/CCD/MA1 9894

UV Spectroscopic Observations of Luminous Narrow-line Seyfert 1 Galaxies

Narrow-line Seyfert 1 galaxies {NLS1s} have remarkably different
properties than Active Galactic Nuclei with broad optical lines. The
most promising explanation for this behavior is that NLS1s have a
higher accretion rate relative to Eddington {L/M} than do broad-line
Seyferts. Despite uniformity in optical line properties, detailed
analysis reveals a divergence of the UV emission line properties that
can be traced differences in the shape of the continuum. A link with
similarly divergent X-ray properties suggests that there may be
variations in L/M even among NLS1s. To test this scenario, we propose
UV spectroscopic of two X-ray extreme NLS1s. These observations offer
the opportunity to advance our understanding in the scatter in the
relationship between line width and black hole mass, to understand
physics of gas in AGN optical and UV emission-line regions, and to
understand recently-discovered peculiar line-less high-z quasars that
may be the early universe counterpart of luminous NLS1s.

ACS/WFC 9891

A snapshot survey of rich stellar clusters in the Large and Small
Magellanic Clouds

Rich stellar clusters are vital to a wide variety of astrophysical
research, from stellar evolution studies to the formation and
evolution of galaxies. In this context, it is important to understand
how rich star clusters form and evolve. The cluster systems in the LMC
and SMC are particularly important in achieving this, because they are
the only systems which contain clusters at all stages of evolution
while being close enough to be studied as fully resolved stellar
populations – although in general this requires the capabilities of
HST. We have recently investigated the structural evolution of LMC and
SMC clusters using archival WFPC2 data, and demonstrated a dramatic
trend in the sizes of these clusters with age. We have shown that this
trend likely represents genuine structural evolution in these
clusters, although it is not clear whether we are observing a
dynamical process or the signature of changing formation conditions.
This result has implications for all astronomical research involving
massive stellar clusters. To develop this work further requires the
extension of our two samples, so that they are statistically
quantifiable. This will allow a number of key questions regarding the
structural evolution trend to be answered. We propose a two-colour
ACS/WFC SNAP survey of rich Magellanic Cloud clusters to achieve this
aim. The unique resolution and sensitivity of ACS/WFC is required for
success, because of the crowded nature of the targets. The SNAP data
will have a large number of additional applications, both to globular
cluster and Magellanic Cloud research.

STIS/CCD/MA2 9886

Boron in F Stars in the Hyades – Insights into the Li-Be Dip

Dramatic deficiencies of Li in the mid-F stars of the Hyades were
discovered by Boesgaard and Tripicco in 1986. Using ultraviolet,
high-resolution spectra from the Keck 10-m telescope, Boesgaard and
King have just discovered the corresponding deficiencies in Be in the
same narrow temperature region in the Hyades. We propose a precision
investigation into the B abundance in the Hyades F stars to ascertain
if there is a B dip. Boron can only be observed with HST and we plan
to use the resonance line of B I at 2497A. Each of these three light
elements is destroyed inside stars, but each has a different threshold
temperature: 2.5 x 10^6, 3.5 x 10^6, and 5 x 10^6 K for Li, Be, and B
respectively. Consequently, these elements survive to increasingly
greater depths in a star and their surface abundances act as a report
on the depth and thoroughness of mixing in the star. The mixing
mechanism in F stars is slow mixing, but not straight convective
mixing. These observations will help determine the nature of the
mixing mechanism{s}, and the connection to stellar rotation. The
abundance of *all three* light elements in a cluster ofknown age and
metallicity provides the necessary information to discern the internal
stellar processes. This mixing must be occurring in other stars of
this mass range {~10-25% more massive than the sun} and can best be
studied in a cluster of stars of common origin and known
characteristics. The Hyades cluster at 7 x 10^8 yr is close enough to
contain stars bright enough for this investigation.

NIC2 9875

The Fundamental Plane of Massive Gas-Rich Mergers

We propose deep NICMOS H-band imaging of a carefully selected sample
of 33 luminous, late-stage galactic mergers. This program is part of a
comprehensive investigation of the most luminous mergers in the nearby
universe, the ultraluminous infrared galaxies {ULIGs}. The
high-resolution HST images will complement an extensive set of
ground-based data that include long-slit NIR spectra from a recently
approved Large VLT Programme. This unique dataset will allow us to
derive with unprecedented precision structural -and- kinematic
parameters for a large unbiased sample of objects spanning the entire
ULIG luminosity function. These data will refine the fundamental plane
of massive gas-rich mergers and enable us to answer the following
questions: {1} Do ultraluminous mergers form elliptical galaxies, and
in particular, giant ellipticals? {2} Do ULIGs evolve into optically
bright QSOs? The results from this detailed study of massive mergers
in the local universe will be relevant to understanding galaxy
formation and evolution at earlier epochs, and in particular, the
dusty sub-mm population that accounts for more than half of the star
formation at z > 1.

NIC/NIC3 9865

The NICMOS Parallel Observing Program

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

ACS/HRC 9853

A Search for Young Binary Brown Dwarfs: Constraining Formation
Scenarios and Masses Through Multiplicity

We propose to use the Advanced Camera for Surveys / High Resolution
Camera to conduct a direct imaging multiplicity survey of 34 young
brown dwarfs in the nearest regions of recent star formation, the T
association Taurus-Auriga and the OB association Upper Scorpius. The
determined multiplicity fraction, the separation distribution, and the
mass ratio distribution will offer stringent observational constraints
on proposed brown dwarf formation scenarios. Moreover, the small
semi-major axes of known field and open cluster brown dwarf binaries
suggest the exciting possibility of our identifying several very close
binaries {< 15 AU}. Continued monitoring of these systems would yield, on a decade timescale, the first dynamical mass estimates of T Tauri brown dwarfs. With masses intermediate between those of stars and planets, brown dwarfs offer our best hope of relating the reasonably well understood processes of star formation to the less well understood processes of planet formation.

ACS/WFC 9847

The Structure and Physics of Extragalactic Jets

As part of an ongoing investigation into the physics of jets, we
propose to obtain ACS polarimetry of the jets of 3C 15, 3C 66B, 3C
346, 3C 371 and PKS 0521-36. This builds on our earlier HST work and
completes a sample of 9 jets that spans the range of jet luminosities
and morphological types. All of these jets have deep, multi-band HST
imaging, and radio polarimetry at matching resolution, and all but one
has Chandra data. Our goal is to investigate three fundamental issues,
brought to light by recent HST and Chandra observations. These are:
{1} What is the energetic and magnetic field structure of jets? {2}
What is the nature of particle acceleration in jets? {3} What is the
nature of the X-ray emission from jets, and what is its relationship
to lower energy emissions? Optical polarimetry provides unique
information about all of these issues. Because of their vastly
different radiative lifetimes {hundreds of years compared to
millions}, optical and radio polarimetry probe different electron
populations and emission regions. Comparison of radio and optical
polarimetry can therefore yield direct information about the
three-dimensional energetic and magnetic field structure of jets.
Optical polarimetry traces the magnetic field configuration in and
near electron acceleration regions, and when combined with optical and
X-ray spectral index maps, polarimetry can yield key constraints about
particle acceleration and the nature of the X-ray emission of jets.

ACS/WFC 9842

A Snapshot Search for Halo Very-Low-Mass Binaries

We propose a snapshot search for binary M subdwarf stars. These nearby
stars have high velocities and low metallicies that identify them as
members of the old Galactic halo {Population II}. ACS imaging is
requested to search for secondary companions. This supplements a
previous snapshot program that only obtained 10 observations. The
observed binary fraction will be compared to the disk M dwarf fraction
to look for differences in star formation. It is likely that a system
suitable for orbital mass determinations will be found. In this case,
future HST observations could determine the first masses for
very-low-mass, low-metallicity stars.