HUBBLE
SPACE TELESCOPE - Continuing to collect World Class Science
DAILY
REPORT # 4531
PERIOD
COVERED: UT January 22, 2007 (DOY 022)
OBSERVATIONS
SCHEDULED
WFPC2
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.
NIC2
10811
Morphology
of a most spectactular Spitzer selected galaxy
By
using ground based sub-millimeter observations to followup
Spitzer-selected
galaxies, we have discovered a starburst dominated
hyperluminous
infrared galaxy. A mid-infrared spectrum obtained with
Spitzer-IRS
provides a redshift of z=1.325, which has been subsequently
confirmed
using both NIR spectroscopy at Keck, and sub-mm spectroscopy
with
IRAM and the CSO. By combining the Spitzer and ground based sub-mm
data,
we measure an integrated IR luminosity of 4 x 10^13 Lsun. This is
the
only such object found in the 9 square degree NDWFS survey, and
hence
is incredibly rare. The only other dusty galaxies this bright show
strong
evidence of AGN activity, but this source does not. One reason
this
object could be so bright is due to lensing, and indeed a
foreground
source spectroscopically confirmed at z=1.034 seems directly
aligned
with the target. However it is unlikely that the geometry of
this
galaxy-galaxy lensing system could support an amplification more
than
a factor of a few. Our IRAC images reveal very faint and red
satellite
systems near our target, hence another possibility is that the
galaxy
is so luminous because of merging induced star-formation
activity.
Morphology is the best way to discriminate between these
hypotheses,
and hence HST observations are essential since the scales on
which
the merging or lensing are occuring are much smaller than what can
be
resolved from the ground.
NIC3
11107
Imaging
of Local Lyman Break Galaxy Analogs: New Clues to Galaxy
Formation
in the Early Universe
We
have used the ultraviolet all-sky imaging survey currently being
conducted
by the Galaxy Evolution Explorer {GALEX} to identify for the
first
time a rare population of low-redshift starbursts with properties
remarkably
similar to high-redshift Lyman Break Galaxies {LBGs}. These
"compact
UV luminous galaxies" {UVLGs} resemble LBGs in terms of size,
SFR,
surface brightness, mass, metallicity, kinematics, dust, and color.
The
UVLG sample offers the unique opportunity of investigating some very
important
properties of LBGs that have remained virtually inaccessible
at
high redshift: their morphology and the mechanism that drives their
star
formation. Therefore, in Cycle 15 we have imaged 7 UVLGs using ACS
in
order to 1} characterize their morphology and look for signs of
interactions
and mergers, and 2} probe their star formation histories
over
a variety of timescales. The images show a striking trend of small-
scale
mergers turning large amounts of gas into vigorous starbursts {a
process
referred to as dissipational or "wet" merging}. Here, we propose
to complete
our sample of 31 LBG analogs using the ACS/SBC F150LP {FUV}
and
WFPC2 F606W {R} filters in order to create a statistical sample to
study
the mechanism that triggers star formation in UVLGs and its
implications
for the nature of LBGs. Specifically, we will 1} study the
trend
between galaxy merging and SFR in UVLGs, 2} artificially redshift
the
FUV images to z=1-4 and compare morphologies with those in similarly
sized
samples of LBGs at the same rest-frame wavelengths in e.g. GOODS,
UDF,
and COSMOS, 3} determine the presence and morphology of significant
stellar
mass in "pre- burst" stars, and 4} study their immediate
environment.
Together with our Spitzer {IRAC+MIPS}, GALEX, SDSS and
radio
data, the HST observations will form a unique union of data that
may
for the first time shed light on how the earliest major episodes of
star
formation in high redshift galaxies came about. This proposal was
adapted
from an ACS HRC+WFC proposal to meet the new Cycle 16 observing
constraints,
and can be carried out using the ACS/SBC and WFPC2 without
compromising
our original science goals.
WFPC2
11038
Narrow
Band and Ramp Filter Closeout
These
observations are to improve calibration of narrow band and ramp
filters.
We also test for changes in the filter properties during
WFPC2's
14 years on-board HST.
WFPC2
11070
WFPC2
CYCLE 15 Standard Darks - part II
This
dark calibration program obtains dark frames every week in order to
provide
data for the ongoing calibration of the CCD dark current rate,
and
to monitor and characterize the evolution of hot pixels. Over an
extended
period these data will also provide a monitor of radiation
damage
to the CCDs.
WFPC2
11084
Probing
the Least Luminous Galaxies in the Local Universe
We
propose to obtain deep color-magnitude data of eight new Local Group
galaxies
which we recently discovered: Andromeda XI, Andromeda XII, and
Andromeda
XIII {satellites of M31}; Canes Venatici I, Canes Venatici II,
Hercules,
and Leo IV {satellites of the Milky Way}; and Leo T, a new
"free-floating"
Local Group dwarf spheroidal with evidence for recent
star
formation and associated H I gas. These represent the least
luminous
galaxies known at *any* redshift, and are the only accessible
laboratories
for studying this extreme regime of galaxy formation. With
deep
WFPC-2 F606W and F814W pointings at their centers, we will
determine
whether these objects contain single or multiple age stellar
populations,
as well as whether these objects display a range of
metallicities.
WFPC2
11202
The
Structure of Early-type Galaxies: 0.1-100 Effective Radii
The
structure, formation and evolution of early-type galaxies is still
largely
an open problem in cosmology: how does the Universe evolve from
large
linear scales dominated by dark matter to the highly non-linear
scales
of galaxies, where baryons and dark matter both play important,
interacting,
roles? To understand the complex physical processes
involved
in their formation scenario, and why they have the tight
scaling
relations that we observe today {e.g. the Fundamental Plane}, it
is
critically important not only to understand their stellar structure,
but
also their dark-matter distribution from the smallest to the largest
scales.
Over the last three years the SLACS collaboration has developed
a
toolbox to tackle these issues in a unique and encompassing way by
combining
new non-parametric strong lensing techniques, stellar
dynamics,
and most recently weak gravitational lensing, with
high-quality
Hubble Space Telescope imaging and VLT/Keck spectroscopic
data
of early-type lens systems. This allows us to break degeneracies
that
are inherent to each of these techniques separately and probe the
mass
structure of early-type galaxies from 0.1 to 100 effective radii.
The
large dynamic range to which lensing is sensitive allows us both to
probe
the clumpy substructure of these galaxies, as well as their
low-density
outer haloes. These methods have convincingly been
demonstrated,
by our team, using smaller pilot-samples of SLACS lens
systems
with HST data. In this proposal, we request observing time with
WFPC2
and NICMOS to observe 53 strong lens systems from SLACS, to obtain
complete
multi-color imaging for each system. This would bring the total
number
of SLACS lens systems to 87 with completed HST imaging and
effectively
doubles the known number of galaxy-scale strong lenses. The
deep
HST images enable us to fully exploit our new techniques, beat down
low-number
statistics, and probe the structure and evolution of
early-type
galaxies, not only with a uniform data-set an order of
magnitude
larger than what is available now, but also with a fully
coherent
and self-consistent methodological approach!
FLIGHT
OPERATIONS SUMMARY:
Significant
Spacecraft Anomalies: (The following are preliminary reports
of
potential non-nominal performance that will be investigated.)
HSTARS:
11158
- GSACQ(1,2,1) failed
GSACQ(1,2,1) at 022/23:35:30 failed to RGA control with QF1STOPF
and
QSTOP flags set. No other flags were seen. Vehicle was LOS at time
of
failure.
REACQ(1,2,1) at 01:17:30 also failed with QF1STOPF and QSTOP flags
set.
REACQ(1,2,1)at 02:58:32 also failed with QF1STOPF and QSTOP flags
set.
Observations affected: WFPC 173 to 181.
COMPLETED
OPS REQUEST: (None)
COMPLETED
OPS NOTES: (None)
SCHEDULED
SUCCESSFUL
FGS
GSacq
06
05
FGS
REacq
08
06
OBAD
with Maneuver
28
28
SIGNIFICANT
EVENTS: (None)