Daily Report # 4428

Notice: Due to the conversion of some ACS WFC or HRC observations into
WFPC2, or NICMOS observations after the loss of ACS CCD science
capability in January, there may be an occasional discrepancy between
a proposal's listed (and correct) instrument usage and the abstract
that follows it.


HUBBLE SPACE TELESCOPE - Continuing to collect World Class Science

DAILY REPORT***** # 4428

PERIOD COVERED: UT August 16, 2007 (DOY 228)

OBSERVATIONS SCHEDULED

ACS/SBC WFPC2 11175

UV Imaging to Determine the Location of Residual Star Formation in
Galaxies Recently Arrived on the Red Sequence

We have identified a sample of low-redshift {z = 0.04 - 0.10} galaxies
that are candidates for recent arrival on the red sequence. They have
red optical colors indicative of old stellar populations, but blue
UV-optical colors that could indicate the presence of a small quantity
of continuing or very recent star formation. However, their spectra
lack the emission lines that characterize star-forming galaxies. We
propose to use ACS/SBC to obtain high- resolution imaging of the UV
flux in these galaxies, in order to determine the spatial distribution
of the last episode of star formation. WFPC2 imaging will provide B,
V, and I photometry to measure the main stellar light distribution of
the galaxy for comparison with the UV imaging, as well as to measure
color gradients and the distribution of interstellar dust. This
detailed morphological information will allow us to investigate the
hypothesis that these galaxies have recently stopped forming stars and
to compare the observed distribution of the last star formation with
predictions for several different mechanisms that may quench star
formation in galaxies.

NIC1/NIC2 11190

Probing Uranus' Vertical Aerosol Structure at Equinox

After a decade of quiescence following the Voyager flybys, Uranus'
atmosphere has been exhibiting increasing activity approaching equinox
that suggests a short timescale, dynamical, response in addition to a
long timescale, radiative, response to the seasonal change of
hemispheric heating. We propose to investigate this dichotomy by
measuring Uranus' vertical aerosol structure over the entire surface,
including both poles, at equinox when the forcing insolation is
hemispherically symmetric, requiring that the sub-Earth latitude be
less than a degree. Only at equinox {every 42 years} can the entire
surface of the planet be viewed {over a full rotation} and mapped with
the same viewing geometry. We will probe the morphology of the
vertical haze structure using NICMOS narrow band filters beyond 1
micron to isolate different altitude regimes between the stratosphere
and cloud deck and investigate its change since Cycle 7. We will use
two complementary approaches: First, imaging will be done using
medium- and narrow-band filters first to locate the
dynamically-produced discrete cloud features, then to probe their
vertical structure and morphology. The methane absorption bands are
stronger in the proposed near-IR {1 to 2.5 microns} than at shorter
wavelengths, and the strong H2 pressure-induced absorption from
2.1-2.4 microns contributes to the peak opacity. This enhances the
visibility of transient, spatially isolated features and allows their
structure to be probed to higher altitudes; namely, to the upper
troposphere where they would be evidence of convective overshoot, a
dynamical manifestation that would support strong seasonally- induced
static instability. In addition to probing the structure with filter
photometry, we will measure longitudinal limb profiles to probe the
vertical background haze distribution vs latitude. HST/NICMOS is
required because it avoids telluric water absorption and OH+O2
emission, and has a stable, well-characterized PSF, essential for limb
studies and extracting the vertical structure of fine features
crossing the disk. The proposed observations would complement the
ground-based Uranus equinox campaign.

NIC1/NIC2/NIC3 8794

NICMOS Post-SAA calibration - CR Persistence Part 5

A new procedure proposed to alleviate the CR-persistence problem of
NICMOS. Dark frames will be obtained immediately upon exiting the SAA
contour 23, and every time 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 DARKs. 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 images. Each observation will need its
own CRMAP, as different SAA passages leave different imprints on the
NICMOS detectors.

NIC2 10802

SHOES-Supernovae, HO, for the Equation of State of Dark energy

The present uncertainty in the value of the Hubble constant {resulting
in an uncertainty in Omega_M} and the paucity of Type Ia supernovae at
redshifts exceeding 1 are now the leading obstacles to determining the
nature of dark energy. We propose a single, integrated set of
observations for Cycle 15 that will provide a 40% improvement in
constraints on dark energy. This program will observe known Cepheids
in six reliable hosts of Type Ia supernovae with NICMOS, reducing the
uncertainty in H_0 by a factor of two because of the smaller
dispersion along the instability strip, the diminished extinction, and
the weaker metallicity dependence in the infrared. In parallel with
ACS, at the same time the NICMOS observations are underway, we will
discover and follow a sample of Type Ia supernovae at z 1. Together,
these measurements, along with prior constraints from WMAP, will
provide a great improvement in HST's ability to distinguish between a
static, cosmological constant and dynamical dark energy. The Hubble
Space Telescope is the only instrument in the world that can make
these IR measurements of Cepheids beyond the Local Group, and it is
the only telescope in the world that can be used to find and follow
supernovae at z 1. Our program exploits both of these unique
capabilities of HST to learn more about one of the greatest mysteries
in science.

WFPC2 11030

WFPC2 WF4 Temperature Reduction #3

In the fall of 2005, a serious anomaly was found in images from the
WF4 CCD in WFPC2. The WF4 CCD bias level appeared to have become
unstable, resulting in sporadic images with either low or zero bias
level. The severity and frequency of the problem was rapidly
increasing, making it possible that WF4 would soon become unusable if
no work-around were found. Examination of bias levels during periods
with frequent WFPC2 images showed low and zero bias episodes every 4
to 6 hours. This periodicity is driven by cycling of the WFPC2
Replacement Heater, with the bias anomalies occurring at the
temperature peaks. The other three CCDs {PC1, WF2, and WF3} appear to
be unaffected and continue to operate properly. Lowering the
Replacement Heater temperature set points by a few degrees C
effectively eliminates the WF4 anomaly. On 9 January 2006, the upper
set point of the WFPC2 Replacement Heater was reduced from 14.9C to
12.2C. On 20 February 2006, the upper set point was reduced from 12.2C
to 11.3C, and the lower set point was reduced from 10.9C to 10.0C.
These changes restored the WF4 CCD bias level; however, the bias level
has begun to trend downwards again, mimicking its behavior in late
2004 and early 2005. A third temperature reduction is planned for
March 2007. We will reduce the upper set point of the heater from
11.3C to 10.4C and the lower set point from 10.0C to 9.1C. The
observations described in this proposal will test the performance of
WFPC2 before and after this temperature reduction. Additional
temperature reductions may be needed in the future, depending on the
performance of WF4. Orbits: internal 26, external 1.

WFPC2 11128

Time Scales Of Bulge Formation In Nearby Galaxies

Traditionally, bulges are thought to fit well into galaxy formation
models of hierarchical merging. However, it is now becoming well
established that many bulges formed through internal, secular
evolution of the disk rather than through mergers. We call these
objects pseudobulges. Much is still unknown about pseudobulges, the
most pressing questions being: How, exactly, do they build up their
mass? How long does it take? And, how many exist? We are after an
answer to these questions. If pseudobulges form and evolve over longer
periods than the time between mergers, then a significant population
of pseudobulges is hard to explain within current galaxy formation
theories. A pseudobulge indicates that a galaxy has most likely not
undergone a major merger since the formation of the disk. The ages of
pseudobulges give us an estimate for the time scale of this quiescent
evolution. We propose to use 24 orbits of HST time to complete UBVIH
imaging on a sample of 33 nearby galaxies that we have observed with
Spitzer in the mid-IR. These data will be used to measure spatially
resolved stellar population parameters {mean stellar age, metallicity,
and star formation history}; comparing ages to star formation rates
allows us to accurately constrain the time scale of pseudobulge
formation. Our sample of bulges includes both pseudo- and classical
bulges, and evenly samples barred and unbarred galaxies. Most of our
sample is imaged, 13 have complete UBVIH coverage; we merely ask to
complete missing observations so that we may construct a uniform
sample for studying bulge formation. We also wish to compare the
stellar population parameters to a variety of bulge and global galaxy
properties including star formation rates, dynamics, internal bulge
morphology, structure from bulge-disk decompositions, and gas content.
Much of this data set is already or is being assembled. This will
allow us to derive methods of pseudobulge identification that can be
used to accurately count pseudobulges in large surveys. Aside from our
own science goals, we will present this broad set of data to the
community. Thus, we waive proprietary periods for all observations.

WFPC2 11201

Systemic and Internal motions of the Magellanic Clouds: Third Epoch
Images

In Cycles 11 and 13 we obtained two epochs of ACS/HRC data for fields
in the Magellanic Clouds centered on background quasars. We used these
data to determine the proper motions of the LMC and SMC to better than
5% and 15% respectively. These are by far the best determinations of
the proper motions of these two galaxies. The results have a number of
unexpected implications for the Milky Way-LMC-SMC system. The implied
three-dimensional velocities are larger than previously believed, and
are not much less than the escape velocity in a standard 10^12 solar
mass Milky Way dark halo. Orbit calculations suggest the Clouds may
not be bound to the Milky Way or may just be on their first passage,
both of which would be unexpected in view of traditional
interpretations of the Magellanic Stream. Alternatively, the Milky Way
dark halo may be a factor of two more massive than previously
believed, which would be surprising in view of other observational
constraints. Also, the relative velocity between the LMC and SMC is
larger than expected, leaving open the possibility that the Clouds may
not be bound to each other. To further verify and refine our results
we now request an epoch of WFPC2/PC data for the fields centered on 40
quasars that have at least one epoch of ACS imaging. We request
execution in snapshot mode, as in our previous programs, to ensure the
most efficient use of HST resources. A third epoch of data of these
fields will provide crucial information to verify that there are no
residual systematic effects in our previous measurements. More
importantly, it will increase the time baseline from 2 to 5 yrs and
will increase the number of fields with at least two epochs of data.
This will reduce our uncertainties correspondingly, so that we can
better address whether the Clouds are indeed bound to each other and
to the Milky Way. It will also allow us to constrain the internal
motions of various populations within the Clouds, and will allow us to
determine a distance to the LMC using rotational parallax.

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************** 09***************** 09
FGS REacq************** 06***************** 06
OBAD with Maneuver **** 30***************** 30

SIGNIFICANT EVENTS:* (None)