Daily Report # 4342

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 #4342

PERIOD COVERED: UT April 16, 2007 (DOY 106)

OBSERVATIONS SCHEDULED

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.

WFPC2 10809

The nature of "dry" mergers in the nearby Universe

Recent studies have shown that "dry" mergers of red, bulge-dominated
galaxies at low redshift play an important role in shaping today's most
massive ellipticals. These mergers have been identified in extremely deep
ground-based images of red sequence galaxies at z ~ 0.1. The ground-based
images reach surface brightness limits of AB ~ 29, but lack the resolution
to study the morphologies of the galaxies inside the effective radius. Here
we propose to obtain ACS images of a representative sample of 40 of these
red sequence galaxies: 15 ongoing dry mergers, 15 remnants, and 10
undisturbed objects. We will measure the isophote shapes and ellipticities
of the galaxies, their dust content, morphological fine structure {shells
and ripples}, AGN content, and their location on the Fundamental Plane. By
comparing galaxies in different stages of the merging process we can
constrain the amount of gas associated with these red mergers, the effect of
active nuclei, and track structural changes. As two galaxies can be observed
in a single orbit 20 orbits are requested to observe the 40 galaxies.

WFPC2 10829

Secular Evolution at the End of the Hubble Sequence

The bulgeless disk galaxies at the end of the Hubble Sequence evolve at a
glacial pace relative to their more violent, earlier-type cousins. The
causes of their internal, or secular evolution are important because secular
evolution represents the future fate of all galaxies in our accelerating
Universe and is a key ingredient to understanding galaxy evolution in
lower-density environments at present. The rate of secular evolution is
largely determined by the stability of the cold ISM against collapse, star
formation, and the buildup of a central bulge. Key diagnostics of the ISM's
stability are the presence of compact molecular clouds and narrow dust
lanes. Surprisingly, edge-on, pure disk galaxies with circular velocities
below 120 km/s do not appear to contain such dust lanes. We propose to
obtain ACS/WFC F606W images of a well-selected sample of extremely late-type
disk galaxies to measure the characteristic scale size of the cold ISM and
determine if they possess the unstable, cold ISM necessary to drive secular
evolution. Our sample has been carefully constructed to include disk
galaxies above and below the critical circular velocity of 120 km/s where
the dust properties of edge-on disks change so remarkably. We will then use
surface brightness profiles to search for nuclear star clusters and
pseudobulges, which are early indicators that secular evolution is at work,
as well as measure the pitch angle of the dust lanes as a function of radius
to estimate the central mass concentrations.

WFPC2 10886

The Sloan Lens ACS Survey: Towards 100 New Strong Lenses

As a continuation of the highly successful Sloan Lens ACS {SLACS} Survey for
new strong gravitational lenses, we propose one orbit of ACS-WFC F814W
imaging for each of 50 high-probability strong galaxy-galaxy lens
candidates. These observations will confirm new lens systems and permit
immediate and accurate photometry, shape measurement, and mass modeling of
the lens galaxies. The lenses delivered by the SLACS Survey all show
extended source structure, furnishing more constraints on the projected lens
potential than lensed-quasar image positions. In addition, SLACS lenses have
lens galaxies that are much brighter than their lensed sources, facilitating
detailed photometric and dynamical observation of the former. When confirmed
lenses from this proposal are combined with lenses discovered by SLACS in
Cycles 13 and 14, we expect the final SLACS lens sample to number 80--100:
an approximate doubling of the number of known galaxy-scale strong
gravitational lenses and an order-of-magnitude increase in the number of
optical Einstein rings. By virtue of its homogeneous selection and sheer
size, the SLACS sample will allow an unprecedented exploration of the mass
structure of the early-type galaxy population as a function of all other
observable quantities. This new sample will be a valuable resource to the
astronomical community by enabling qualitatively new strong lensing science,
and as such we will waive all but a short {3-month} proprietary period on
the observations.

WFPC2 11024

WFPC2 CYCLE 15 INTERNAL MONITOR

This calibration proposal is the Cycle 15 routine internal monitor for
WFPC2, to be run weekly to monitor the health of the cameras. A variety of
internal exposures are obtained in order to provide a monitor of the
integrity of the CCD camera electronics in both bays {both gain 7 and gain
15 -- to test stability of gains and bias levels}, a test for quantum
efficiency in the CCDs, and a monitor for possible buildup of contaminants
on the CCD windows. These also provide raw data for generating annual
super-bias reference files for the calibration pipeline.

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.

WFPC2 10925

Imaging the Nearest Damped Lyman Alpha Absorbers

We propose to acquire broad-band and H-alpha imaging of three bright, very
nearby host galaxies for damped Ly-alpha absorbers {DLAs}. Our targets are
the only DLA hosts at z 0.03 {i.e., spatial resolutions of 1.2 kpc}. The
purpose of these observations is to discover the detailed morphology and
kinematics and thus the origins of the gas giving rise to DLAs. While
ground-based spectroscopy of DLAs is used to infer indirectly the evolution
of galaxy metallicity and thick disk kinematics out to z 4, only with HST
imaging of the very lowest redshift DLA galaxies can we discover these
relationships directly. In conjunction with H I 21-cm VLA emission maps,
broad-band and H-alpha images of these DLAs will allow us to determine: {1}
the sites of active star formation in the host galaxies and their
relationship to the QSO sightline, {2} the presence of stellar streams,
supernova shells, or bipolar "superwind" outflows in DLA host galaxies, and
{3} the detailed spiral structure of the host galaxies, which will allow us
to use the lower resolution H I 21-cm emission line images to determine
unambiguous DLA kinematics with respect to the host galaxy {i.e., is the DLA
rotating with the disk?}. Thus, the high resolution imaging will allow us to
correctly interpret the kinematics and metallicity information provided by
the H I 21-cm VLA maps and HST UV spectroscopy to better inform the high-z
results.

WFPC2 11023

WFPC2 CYCLE 15 Standard Darks - part 1

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 11079

Treasury Imaging of Star Forming Regions in the Local Group: Complementing
the GALEX and NOAO Surveys

We propose to use WFPC2 to image the most interesting star-forming regions
in the Local Group galaxies, to resolve their young stellar populations. We
will use a set of filters including F170W, which is critical to detect and
characterize the most massive stars, to whose hot temperatures colors at
longer wavelengths are not sensitive. WFPC2's field of view ideally matches
the typical size of the star-forming regions, and its spatial resolution
allows us to measure indvidual stars, given the proximity of these galaxies.
The resulting H- R diagrams will enable studies of star-formation properties
in these regions, which cover largely differing metallicities {a factor of
17, compared to the factor of 4 explored so far} and characteristics. The
results will further our understanding of the star-formation process, of the
interplay between massive stars and environment, the properties of dust, and
will provide the key to interpret integrated measurements of star-formation
indicators {UV, IR, Halpha} available for several hundreds more distant
galaxies. Our recent deep surveys of these galaxies with GALEX {FUV, NUV}
and ground-based imaging {UBVRI, Halpha, [OIII] and [SII]} provided the
identification of the most relevant SF sites. In addition to our scientific
analysis, we will provide catalogs of HST photometry in 6 bands, matched
corollary ground-based data, and UV, Halpha and IR integrated measurements
of the associations, for comparison of integrated star-formation indices to
the resolved populations. We envisage an EPO component.

FLIGHT OPERATIONS SUMMARY:

Significant Spacecraft Anomalies: (The following are preliminary reports of
potential non-nominal performance that will be investigated.)

HSTARS: (None)

COMPLETED OPS REQUEST: (None)

COMPLETED OPS NOTES: (None)

SCHEDULED SUCCESSFUL

FGS GSacq 07 07
FGS REacq 06 06
OBAD with Maneuver 24 24

SIGNIFICANT EVENTS: (None)