Daily Report # 4324
- From: "Cooper, Joe" <jcooper@xxxxxxxxxxxx>
- Date: Thu, 22 Mar 2007 13:53:07 +0000 (UTC)
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)
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