Notice: For the foreseeable future, the daily reports may
contain
apparent discrepancies between some proposal descriptions
and the listed
instrument usage. This is due to the conversion of
previously approved
ACS WFC or HRC observations into WFPC2, or NICMOS
observations
subsequent to the loss of ACS CCD science capability in
late January.
HUBBLE SPACE TELESCOPE - Continuing to collect World Class
Science
DAILY REPORT # 4324
PERIOD COVERED: UT March 21, 2007 (DOY 080)
OBSERVATIONS SCHEDULED
WFPC2 10563
Accurate dark-matter mass profiles in 3 elliptical
galaxies as a test of
CDM
A critical test of the successful Lambda-CDM picture for
structure
formation is the measurement of the power law exponent,
gamma, of the
centre of dark matter density profiles, predicted to lie
in the range
1.0-1.5. Measurements of gamma derived from rotation
curves of LSB
galaxies appear to contradict CDM, but rely on assumptions
that are
difficult to verify {e.g. axisymmetry}. We have recently
demonstrated,
using our new `semi- linear' inversion method, how strong
gravitational
lensing by galaxies can provide a clean and accurate
measurement of
gamma, free of such ambiguities. HST images of lensed
non-AGN galaxies
provide hundreds of resolution elements, each a constraint
on the mass
profile. Such lenses are exceedingly rare, but we have
recently
discovered new systems. We propose deep ACS-HRC
observations of 3
systems to measure gamma in each, accurate to 0.15 {95%
confidence} and
to obtain an indication of its variation between galaxies.
To establish
the required number of orbits we have undertaken an
end-to-end
simulation of the problem, creating and analysing
synthetic ACS images.
Additionally the semi-linear method simultaneously
reconstructs the
pixelised source surface brightness distribution. Our
simulations
demonstrate that the fine sampling and small pixel
scattering of the
HRC, resolves the morphology of the sources with exquisite
detail.
WFPC2 10833
Host Galaxies of Reverberation Mapped AGNs
We propose to obtain unsaturated high-resolution images of
17
reverberation-mapped active galactic nuclei in order to
remove the
point-like nuclear light from each image, thus yielding a
"nucleus-free"
image of the host galaxy. This will allow investigation of
host galaxy
properties: our particular interest is determination of
the host-galaxy
starlight contribution to the reverberation-mapping
observations. This
is necessary {1} for accurate determination of the
relationship between
the AGN nuclear continuum flux and the size of the broad
Balmer-line
emitting regions of AGNs, which is important in estimating
black hole
masses for large samples of QSOs, and {2} for accurate
determination of
the bolometric luminosity of the AGN proper. Through
observations in
Cycles 12 and 14, we have obtained or will obtain images
of 18 of the 35
objects in the reverberation-mapping compilation of
Peterson et al.
{2004}. These observations revealed that the host-galaxy
contribution,
even in the higher-luminosity AGNs, is higher than
expected and that all
of the reverberation- mapped AGNs will have to be
observed, not just the
lower-luminosity sources; each source is different, and
each source is
important. Therefore we request time to observe the 17
remaining
reverberation-mapped AGNs.
WFPC2 10877
A Snapshot Survey of the Sites of Recent, Nearby
Supernovae
During the past few years, robotic {or nearly robotic}
searches for
supernovae {SNe}, most notably our Lick Observatory
Supernova Search
{LOSS}, have found hundreds of SNe, many of them in quite
nearby
galaxies {cz < 4000 km/s}. Most of the objects were
discovered before
maximum brightness, and have follow-up photometry and
spectroscopy; they
include some of the best-studied SNe to date. We propose
to conduct a
snapshot imaging survey of the sites of some of these
nearby objects, to
obtain late-time photometry that {through the shape of the
light and
color curves} will help reveal the origin of their
lingering energy. The
images will also provide high-resolution information on
the local
environments of SNe that are far superior to what we can
procure from
the ground. For example, we will obtain color-color and
color-magnitude
diagrams of stars in these SN sites, to determine the SN
progenitor
masses and constraints on the reddening. Recovery of the
SNe in the new
HST images will also allow us to actually pinpoint their
progenitor
stars in cases where pre- explosion images exist in the
HST archive.
This proposal is an extension of our successful Cycle 13
snapshot survey
with ACS. It is complementary to our Cycle 15 archival
proposal, which
is a continuation of our long-standing program to use
existing HST
images to glean information about SN environments.
NIC2 10798
Dark Halos and Substructure from Arcs & Einstein Rings
The surface brightness distribution of extended
gravitationally lensed
arcs and Einstein rings contains super-resolved
information about the
lensed object, and, more excitingly, about the smooth and clumpy
mass
distribution of the lens galaxies. The source and lens
information can
non-parametrically be separated, resulting in a direct
"gravitational
image" of the inner mass-distribution of
cosmologically-distant galaxies
{Koopmans 2005; Koopmans et al. 2006 [astro-ph/0601628]}.
With this goal
in mind, we propose deep HST ACS-F555W/F814W and
NICMOS-F160W WFC
imaging of 20 new gravitational-lens systems with
spatially resolved
lensed sources, of the 35 new lens systems discovered by
the Sloan Lens
ACS Survey {Bolton et al. 2005} so far, 15 of which are
being imaged in
Cycle-14. Each system has been selected from the SDSS and
confirmed in
two time- efficient HST-ACS snapshot programs {cycle
13&14}.
High-fidelity multi-color HST images are required {not delivered
by the
420s snapshots} to isolate these lensed images {properly
cleaned,
dithered and extinction-corrected} from the lens galaxy
surface
brightness distribution, and apply our "gravitational
maging" technique.
Our sample of 35 early-type lens galaxies to date is by
far the largest,
still growing, and most uniformly selected. This minimizes
selection
biases and small-number statistics, compared to smaller,
often
serendipitously discovered, samples. Moreover, using the
WFC provides
information on the field around the lens, higher S/N and a
better
understood PSF, compared with the HRC, and one retains
high spatial
resolution through drizzling. The sample of galaxy mass
distributions -
determined through this method from the arcs and Einstein
ring HST
images - will be studied to: {i} measure the smooth mass
distribution of
the lens galaxies {dark and luminous mass are separated
using the HST
images and the stellar M/L values derived from a joint
stellar-dynamical
analysis of each system}; {ii} quantify statistically and
individually
the incidence of mass-substructure {with or without
obvious luminous
counter- parts such as dwarf galaxies}. Since dark-matter
substructure
could be more prevalent at higher redshift, both results
provide a
direct test of this prediction of the CDM hierarchical
structure-formation model.
ACS/SBC 10815
The Blue Hook Populations of Massive Globular Clusters
Blue hook stars are a class of hot {~35,000 K} subluminous
horizontal
branch stars that have been recently discovered using HST
ultraviolet
images of the globular clusters omega Cen and NGC 2808.
These stars
occupy a region of the HR diagram that is unexplained by
canonical
stellar evolution theory. Using new theoretical
evolutionary and
atmospheric models, we have shown that the blue hook stars
are very
likely the progeny of stars that undergo extensive
internal mixing
during a late helium core flash on the white dwarf cooling
curve. This
"flash mixing" produces an enormous enhancement
of the surface helium
and carbon abundances, which suppresses the flux in the
far ultraviolet.
Although flash mixing is more likely to occur in stars
that are born
with high helium abundances, a high helium abundance, by
itself, does
not explain the presence of a blue hook population - flash
mixing of the
envelope is required. We propose ACS ultraviolet
{SBC/F150LP and
HRC/F250W} observations of the five additional globular
clusters for
which the presence of blue hook stars is suspected from
longer
wavelength observations. Like omega Cen and NGC 2808,
these five targets
are also among the most massive globular clusters, because
less massive
clusters show no evidence for blue hook stars. Because our
targets span
1.5 dex in metallicity, we will be able to test our
prediction that
flash-mixing should be less drastic in metal-rich blue
hook stars. In
addition, our observations will test the hypothesis that
blue hook stars
only form in globular clusters massive enough to retain
the helium-
enriched ejecta from the first stellar generation. If this
hypothesis is
correct, then our observations will yield important
constraints on the
chemical evolution and early formation history in globular
clusters, as
well as the role of helium self-enrichment in producing
blue horizontal
branch morphologies and multiple main sequence turnoffs.
Finally, our
observations will provide new insight into the formation
of the hottest
horizontal branch stars, with implications for the origin
of the hot
helium-rich subdwarfs in the Galactic field.
NIC1/NIC2/NIC3 8795
NICMOS Post-SAA calibration - CR Persistence Part 6
A new proceedure proposed to alleviate the CR-persistence
problem of
NICMOS. Dark frames will be obtained immediately upon
exiting the SAA
contour 23, and everytime 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 i
mages. Each observation will need its own CRMAP, as
different SAA
passages leave different imprints on the NICMOS detectors.
NIC3 11080
Exploring the Scaling Laws of Star Formation
As a variety of surveys of the local and distant Universe
are
approaching a full census of galaxy populations, our
attention needs to
turn towards understanding and quantifying the physical
mechanisms that
trigger and regulate the large-scale star formation rates
{SFRs} in
galaxies.
WFPC2 10890
Morphologies of the Most Extreme High-Redshift
Mid-IR-Luminous Galaxies
The formative phase of the most massive galaxies may be
extremely
luminous, characterized by intense star- and
AGN-formation. Till now,
few such galaxies have been unambiguously identified at
high redshift,
restricting us to the study of low-redshift ultraluminous
infrared
galaxies as possible analogs. We have recently discovered
a sample of
objects which may indeed represent this early phase in
galaxy formation,
and are undertaking an extensive multiwavelength study of
this
population. These objects are bright at mid-IR wavelengths
{F[24um]>0.8mJy}, but deep ground based imaging
suggests extremely faint
{and in some cases extended} optical counterparts
{R~24-27}. Deep K-band
images show barely resolved galaxies. Mid-infrared
spectroscopy with
Spitzer/IRS reveals that they have redshifts z ~ 2-2.5,
suggesting
bolometric luminosities ~10^{13-14}Lsun! We propose to
obtain deep ACS
F814W and NIC2 F160W images of these sources and their
environs in order
to determine kpc-scale morphologies and surface photometry
for these
galaxies. The proposed observations will help us determine
whether these
extreme objects are merging systems, massive obscured
starbursts {with
obscuration on kpc scales!} or very reddened {locally
obscured} AGN
hosted by intrinsically low-luminosity galaxies.
FLIGHT OPERATIONS SUMMARY:
Significant Spacecraft Anomalies: (The following are
preliminary reports
of potential non-nominal performance that will be
investigated.)
HSTARS:
10749 - GSAcq(1,2,1) failed to RGA Hold (Gyro Control)
GSAcq(1,2,1) scheduled at 080/17:33:49 - 080/17:41:54 failed to RGA Hold
due
to (QF1STOPF) stop flag indication on FGS1. Pre-acq OBADs
showed(RSS)
attitude correction values of 1856.02 and 12.04 arcseconds.
Post-acq OBAD/MAP had 3-axis error (RSS) value of 272.93 arcseconds.
COMPLETED OPS REQUEST: (None)
COMPLETED OPS NOTES: (None)
SCHEDULED
SUCCESSFUL
FGS GSacq
09
08
FGS REacq
05
05
OBAD with Maneuver
28
28
SIGNIFICANT EVENTS: (None)