HST Daily Report # 3302 Part 1
HUBBLE SPACE TELESCOPE
DAILY REPORT # 3302
PERIOD COVERED: DOYs 45-49
Note:† This report contains a summary over the last several days
scheduled
science
proposals only. No spacecraft status. Goddard was closed due to snow.
OBSERVATIONS SCHEDULED
ACS 9472
A Snapshot Survey for Gravitational Lenses among z >= 4.0 Quasars
Over the last few years, the Sloan Digital Sky Survey has revolutionized
the
study of high-redshift quasars by discovering over 200 objects with
redshift
greater than 4.0, more than doubling the number known in this redshift
interval.
The sample includes eight of the ten highest redshift quasars known. We
propose
a snapshot imaging survey of a well-defined sample of 250 z > 4.0 quasars
in
order to find objects which are gravitationally lensed. Lensing models
including
magnification bias predict that at least 4% of quasars in a flux-limited
sample
at z > 4 will be multiply lensed. Therefore this survey should find of
order 10
lensed quasars at high redshift; only one gravitationally lensed quasar
is
currently known at z > 4. This survey will provide by far the best sample
to
date of high-redshift gravitational lenses. The observed fraction of
lenses can
put strong constraints on cosmological models, in particular on the
cosmological
constant Lambda. In addition, magnification bias can significantly bias
estimates of the luminosity function of quasars and the evolution
thereof; this
work will constrain how important an effect this is, and thereby give us
a
better understanding of the evolution of quasars and black holes at early
epochs, as well as constrain models for black hole formation.
ACS 9658
ACS Earth Flats
This program will obtain sequences of flat field images by observing the
bright
Earth. Several UV filters from the interim calibration program {9564}
require
additional exposures to obtain the required illumination. A few UV
filters from
this program will be repeated to monitor for changes in the flat fields
and to
verify the interim results. Since no streaks are observed in the UV, the
wavelength coverage is extended to longer wavelengths in order to explore
the
severity of streaks in the flats from clouds in the FOV. We have added
exposures
for the HRC in the visible filters to verify the results derived from the
L-flat
campaign and to explore the severity of streaks. We have also added
exposures on
WFC using the minimum exposure time and using filters which will not
saturate
the brightest WFC pixel by more than 10 times the full well.
ACS 9463
Are OH/IR stars the youngest post-AGB stars? An ACS SNAPshot imaging
survey
Essentially all well-characterized preplanetary nebulae {PPNs}– 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
propose an ACS/SNAPshot imaging survey of a large, morphologically
unbiased
sample of these objects, selected using their IRAS 12-to-25micron colors.
Our
ground-based imaging study of OH/IR stars has revealed a few compact
bipolar
objects, supporting our hypothesis. However since most objects remain
unresolved, HST observations are needed to determine how and when the
bipolar
geometry asserts itself. 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 PPNs, are common or rare phenomena.
ACS 9673
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 9480
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 9293
Massive Black Holes in Early Type Galaxies
Recently, a nearly perfect relation has been recognized between the
masses of
the black holes {for 3×10^6 Msun < M_BH < 3×10^9 Msun} at the centers of
galaxies and the velocity dispersions of their bulges. However,
uncertainties
over the exact slope of the correlation still remain, and it is not known
if
such a relation extends to black holes of lower and higher masses. The
discovery
of small {r ~ a few hundred pc}, well defined, dust and gas disks in the
nuclei
of some active elliptical galaxies opened a new avenue for measuring
central
mass distributions. When ionized gas is present, a small number of high
spatial
resolution {e.g. STIS} spectra are sufficient to characterize the disk
dynamics
and the galaxy’s central mass {e.g., M87, M81, NGC 4374}. We propose to
use
STIS
spectroscopy to measure black hole masses, using gas dynamics, in the
centers of
several brightest cluster galaxies {BCGs}, 2 nearby galaxies with low
velocity
dispersions, and a number of elliptical galaxies known to harbor small
nuclear
dust disks. The proposed targets encompass a wide range of black hole
masses,
allowing us to fully examine the M_BH — sigma relationship. We will also
obtain
H-alpha and continuum images to fully characterize the gaseous and dust
morphology as well as stellar surface profile in the central regions.
ACS 9411
Morphologies and faint neighbors of z=4.5 Lyman Alpha Emitting Galaxies
We propose to image one ACS field containing four spectroscopically
confirmed
Ly-alpha emitters at z=4.5 in restframe UV and a narrowband filter
containing
the Ly-alpha line. These observations will {A} Reveal the morphology of
the
four
spectroscopically confirmed sources. The high equivalent widths of the
Ly-alpha
line in these four galaxies in particular and this population in general
cannot
be explained without invoking one or more of: extreme youth of the
stellar
population, zero metallicity, energetic winds or type II quasars.
Comparison of
morphologies in the line and continuum would help favor or rule out some
of
these possibilities. This would also tell us whether the star-formation
is
uniformly distributed or centrally concentrated or concentrated but in
many
clumps? Proximity of these galaxies {average projected physical
separation of
200 kpc, with one pair 30 kpc apart} also makes interactions likely. {B}
Extend
the luminosity function of Ly-alpha sources by 2.5 magnitudes due to
better
spatial resolution of HST and sensitivity of ACS. We will be able to
detect
sources with line flux of ~eq 2 * 10^-18 ergcm2s over 11.5 sq-arcmins {~
100
sources}. This complements the LALA {Large Area Lyman Alpha} survey which
covers
1/3 square-degree to a line sensitivity of ~eq 2 * 10^- 17. Thus we get a
picture of this patch of young universe in two ways: statistics of faint
galaxies and morphologies of relatively bright ones.
ACS 9656
Stability of the ACS CCD: geometry, flat fielding, photometry
A moderately crowded stellar field, located ~6′ West of the centre of the
cluster 47 Tuc, is observed repeatedly {every three weeks with the WFC,
every
other month with the HRC} in various filters, spending 1 orbit per epoch.
Different filters will be used every time, so that over the course of the
year
all filters will have been employed at least twice. The most common
filters
will
be checked more frequently. The same field has been observed in the
course of
the SMOV phase and the positions and magnitudes of the most prominent
stars
have
been accurately measured. Although the field is neither a proper
astrometric nor
a proper photometric standard one, the positions and magnitudes of the
objects
in it can be used to monitor any local and large scale variations in the
platescale and sensitivity of the detectors. It should be noted that for
the
filters which have already been used during the SMOV phase it will be
sufficient
to take one single image, without CR-SPLIT, since the exposure time is
always
short {20-30 sec} and there will be so many stars that the few of them
which are
affected by cosmic rays can be discarded as outliers in the photometry.
For
narrow and medium band filters not exercised on this target in the SMOV
phase,
however, a baseline will have to be set. This expenditure of time will
apply to
the current cycle only. At variance with the approach used in SMOV, there
is no
need for large telescope slews to place the same objects on opposite
sides of
the detectors, thence allowing the programme to remain compact and
efficient.
All exposure level parameters are set to their default values, except for
the
amplifier gain of the WFC exposures in the F606W band, which will be
collected
with the gain value of 2 for the WFC for compatibility with the SMOV
observations. The exposure time is typically 30 seconds for the WFC, 60
sec for
the HRC. No attempt will be made to attain a predefined or the same
orientation
on the sky amongst different epochs. Typically, for the WFC, five
exposures
will
be accommodated in one orbit. For the HRC, about 10 exposures can be
fitted
within one orbit
ACS 9462
Systemic and Internal Proper Motions of the Magellanic Clouds from
Astrometry
with ACS
We request first epoch observations with ACS of Magellanic Cloud fields
centered
on background quasars. Second epoch observations will be requested ~ 5
years
later to allow the measurement of the systemic and internal proper
motions of
the Clouds with error <~0.05 mas/year. These motions are of fundamental
importance. The systemic motions of the LMC and SMC probe the
gravitational
potential of the dark halo. The internal proper motion due to rotation
can be
exploited to yield a rotational parallax distance to the LMC; the first
time
that this will be done for any galaxy. This is particularly important for
the
LMC because of its crucial role in the extragalctic distance ladder.
Previous
measurements of the proper motion of the LMC yield a systemic component
ranging
from 1.4 mas/year to 3.4 mas/year {differing by several times the quoted
errors}, with no useful determination of the internal motions. The main
problem
with measurements of the proper motion of the LMC has been the lack of a
sample
of background quasars to use as reference frame. We have recently been
able to
identify a sample of 54 quasars behind the Magellanic Clouds from their
variability characteristics in the MACHO database. With this sample and
the
advent of ACS an accurate proper motion measurement has become possible
for the
very first time.
ACS 9352
The Deceleration Test from Treasury Type Ia Supernovae at Redshifts 1.2
to 1.6
Type Ia supernovae {SNe Ia} provide the only direct evidence for an
accelerating
universe, an extraordinary result that needs a rigorous test. The case
for
cosmic acceleration rests on the observation that SNe Ia at z ~ 0.5 are ~
0.25
mag fainter than they would be in a universe without acceleration. A
powerful
and straightforward way to assess the reliability of the SN Ia
measurement and
the conceptual framework of its interpretation is to look for cosmic
deceleration at z >= 1. This would be a clear signature of a mixed
dark-matter
and dark-energy universe. Systematic errors in the SN Ia result
attributed to
grey dust or cosmic evolution of the SN Ia peak luminosity would not show
this
change of sign. We have demonstrated proof of this concept with a single
SN Ia,
SN 1997ff at z = 1.7, found and followed by HST. The results suggest an
early
epoch of deceleration, but this is too important a conclusion to rest on
just
one object. Here we propose to use HST for observations of six SNe Ia in
the
range 1.2 <= z <= 1.6, that will be discovered as a byproduct from
proposed
Treasury programs for high-latitude ACS surveys. Six objects will provide
a
much
firmer foundation for a conclusion that touches on important questions of
fundamental physics.
ACS/HRC 9391
High-Resolution Imaging of Pluto’s Surface
We will collect a series of observations with the ACS/HRC from which we
will
derive a two-color global map of Pluto’s surface. We will image Pluto at
F435W
and F555W, wavelengths that have been extensively studied from the ground
over
the past 50 years. The maps will provide albedos with accurate error
determinations down to 52 degrees South latitude. These observations will
provide a second epoch of HST mapping of the active surface of Pluto as
it
continues to recede from the Sun and will provide an important context
for
other
detailed studies of Pluto.
ACS/STIS 9451
ACS Imaging and STIS Spectroscopy of Binary Brown Dwarfs
We have compiled a sample of 9 spatially resolved binary brown dwarfs {18
objects}, and now propose ACS imaging and STIS spectroscopic follow-up
observations. While theoretical models on the interplay of chemical and
physical
processes governing brown dwarf atmospheres have reached a high level of
sophistication, interpretation of observational data remains difficult.
As
brown
dwarfs never stabilize themselves on the hydrogen main sequence, there is
always
an ambiguity between the temperature or luminosity of any brown dwarf and
its
mass or age. The individual components of brown dwarf binaries, however,
are
expected to be coeval and have the same underlying chemical composition.
This
provides crucial constraints on any model, thus greatly reducing the
number of
the free parameters. The aim is to obtain photometric and spectroscopic
data to
probe the physical and chemical properties of the brown dwarf
atmospheres, as
well as second epoch astrometric data to characterize th e orbital
motion. The
study will provide important feedback on theoretical model atmospheres
and
evolutionary tracks for brown dwarfs. As such, it will be an important
step
towards a better understanding of objects with spectral properties
intermediate
between those of giant planets and late-type stars.
ACS/WFC 9584
ACS Default {Archival} Pure Parallel Program II.
The Advanced Camera for Surveys (WFC) was used to test ACS pure
parallels.
ACS/WFC 9575
Default {Archival} Pure Parallel Program.
The Advanced Camera for Surveys (WFC) was used to test ACS pure parallels
in
POMS.
ACS/WFC 9492
Extragalactic Distances: the Need for Accurate Photometry of Blue
Supergiants
and Cepheids
The investigation of the Wind Momentum-Luminosity Relationship {WLR} of
blue
supergiant stars as an independent extragalactic distance indicator has
reached
a critical phase. Following our recent discovery and spectroscopic
follow-up of
several tens of stars outside of the Local Group in NGC 300 and NGC 3621,
we can
now calibrate the WLR in terms of spectral subtype and metallicity with a
higher
accuracy than hithertho possible with the statistically limited samples
available in the nearby galaxies studied so far. This, however, requires
high-resolution imaging to obtain accurate BVI photometry of a
significant
fraction of those stars for which we have spectroscopic information. This
can be
effectively accomplished with eight ACS/WFC fields in these two galaxies.
As a
further step, we can use the calibrated WLR to measure the first
independent
extragalactic distance. We then propose additional imaging of six ACS/WFC
fields
in M101 to select blue supergiant candidates for spectroscopic follow-up.
Having
recently discovered more than a hundred new Cepheids in NGC 300, the
high-resolution imaging proposed for the photometry of blue supergiants
can
also
be used, with no additional observing effort, to verify the effects of
blending
on the Cepheid distance to this galaxy, an important calibrator of
secondary
distance indicators.
ACS/WFPC2 9481
Pure Parallel Near-UV Observations with WFPC2 within High-Latitude ACS
Survey
Fields
In anticipation of the allocation of ACS high-latitude imaging survey{s},
we
request a modification of the default pure parallel program for those
WFPC2
parallels that fall within the ACS survey field. Rather than duplicate
the red
bands which will be done much better with ACS, we propose to observe in
the
near-ultraviolet F300W filter. These data will enable study of the
rest-frame
ultraviolet morphology of galaxies at 0<z<1. We will determine the
morphological
k-correction, and the location of star formation within galaxies, using a
sample
that is likely to be nearly complete with multi-wavelength photometry and
spectroscopic redshifts. The results can be used to interpret
observations of
higher redshift galaxies by ACS.
FGS 9347
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.
FGS 9711
FGS Scattered Earthlight Test Proposal
The purpose behind this proposal is to capture fairly high-fidelity data
on how
the scattered earth light {both bright and dark earth limb} affects FGS
performance during guiding.
FGS 9348
The Distances to AM CVn stars
We propose to determine the parallaxes and proper motions of the five
brightest
of the seven known AM CVn systems using the HST Fine Guidance Sensors. AM
CVn
systems are binaries where mass is transferred from a completely
hydrogen-deficient, degenerate mass donor to a white dwarf primary
through a
helium accretion disk. A better understanding of these systems is crucial
for a
number of reasons:, to study the late stages of binary evolution, to
study the
effect of chemical composition on the physics of accretion discs; , o to
estimate their contribution to the Supernovae Ia rate and , to estimate
their
contribution to the gravitational radiation background. All these studies
rely
critically on a determination of the distances to the currently known
systems.
With brightnesses in the range 13<V<17 and estimated distances <400pc
they are
ideal targets for the HST-FGS.
HST 9382
A Large Targeted Survey for z < 1.6 Damped Lyman Alpha Lines in SDSS QSO
MgII-FeII Systems.
We have searched the first public release of SDSS QSO spectra for low-z
{z<1.65}
metal absorption lines and found over 200 large rest equivalent width
MgII-FeII
systems. Previously, we empirically showed that such systems are good
tracers of
large neutral gas columns, with ~50% being classical damped Lyman alpha
{DLA}
systems {N_HI>=2*10^20 cm^-2}. Here we propose to follow up a
well-defined
subset of 79 of them to search for DLAs with 0.47<z<1.60. Only QSOs
brighter
than g’=19 were selected. The QSO emission and DLA absorption redshifts
were
constrained to virtually eliminate data loss due to intervening Lyman
limit
absorption. Consequently, we expect to discover ~40 new DLAs, which is a
three-fold increase in this redshift interval. This will significantly
improve
our earlier low-z DLA statistical results on their incidence,
cosmological mass
density, and N_HI distribution. The results will also allow us to better
quantify the empirical DLA — metal-line correlation. With this improved
understanding, the need for follow-up UV spectroscopy will lessen and,
with the
release of the final database of SDSS QSO spectra {an ~25-fold increase},
the
number of low-z DLAs could be increased arbitrarily. Thus, the power of
the
large and statistically-sound SDSS database in combination with a proven
technique for finding low-z DLAs will, over the next few years,
essentially
solve the problem of making an accurate determination of the cosmic
evolution of
the neutral gas component down to z~0.4.
