HUBBLE
SPACE TELESCOPE - Continuing to collect World Class Science
DAILY
REPORT # 4499
PERIOD
COVERED: UT December 4, 2007 (DOY 338)
OBSERVATIONS
SCHEDULED
ACS/SBC
10907
New
Sightlines for the Study of Intergalactic Helium: A Dozen
High-Confidence,
UV-Bright Quasars from SDSS/GALEX
The
reionization of intergalactic helium is thought to have occurred
between
redshifts of about 3 and 4. Detailed study of HeII Lyman-alpha
absorption
toward a handful quasars at 2.7<z<3.3 demonstrates the great
potential
of such probes of the IGM, but the current critically-small
sample
limits confidence in resulting cosmological inferences. The
requisite
unobscured quasar sightlines to high-redshift are extremely
rare,
especially due to severe absorption in random intervening
Lyman-limit
systems, but SDSS provides thousands of z>3.1 quasars
potentially
suitable for HeII studies. We have cross-correlated SDSS
quasars
with GALEX UV sources to obtain a dozen new, very
high-confidence,
candidate quasars/sightlines {z=3.1 to 4.1} potentially
useful
for detailed HeII studies even with current HST instruments. We
propose
brief, 2-orbit per target, reconnaissance spectral exposures
with
the ACS SBC prism to definitively verify UV flux down to the HeII
break.
Our combined SDSS/GALEX selection insures a very high-yield of
confirmations,
as the quasars are already known to be UV-bright from
broadband
GALEX images. The additional sightlines, extending to very
high-redshift,
will directly enable ensemble spectral stacks, as well as
long
exposure follow-up spectra, at high S/N with the ACS/SBC
ultraviolet
prisms {or perhaps STIS or
measure
the spectrum and evolution of the ionizing background radiation,
the
evolution of HeII opacity, and the density of intergalactic baryons.
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
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
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
11197
Sweeping
Away the Dust: Reliable Dark Energy with an Infrared Hubble
Diagram
We
propose building a high-z Hubble Diagram using type Ia supernovae
observed
in the infrared rest-frame J-band. The infrared has a number of
exceptional
properties. The effect of dust extinction is minimal,
reducing
a major systematic that may be biasing dark energy
measurements.
Also, recent work indicates that type Ia supernovae are
true
standard candles in the infrared meaning that our Hubble diagram
will
be resistant to possible evolution in the Phillip's relation over
cosmic
time. High signal-to-noise measurements of 16 type Ia events at
z~0.4
will be compared with an independent optical Hubble diagram from
the
ESSENCE project to test for a shift in the derived dark energy
equation
of state due to a systematic bias. In Cycle 15 we obtained
NICMOS
photometry of 8 ESSENCE supernovae and are awaiting template
observations
to place them on the IR Hubble diagram. Here we request
another
8 supernovae be studied in the final season of the ESSENCE
search.
Because of the bright sky background, H-band photometry of z~0.4
supernovae
is not feasible from the ground. Only the superb image
quality
and dark infrared sky seen by HST makes this test possible. This
experiment
may also lead to a better, more reliable way of mapping the
expansion
history of the universe with the Joint Dark Energy Mission.
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
11029
WFPC2
CYCLE 15 Intflat Linearity Check and Filter Rotation Anomaly
Monitor
Intflat
observations will be taken to provide a linearity check: the
linearity
test consists of a series of intflats in F555W, in each gain
and
each shutter. A combination of intflats, visflats, and earthflats
will
be used to check the repeatability of filter wheel motions.
{Intflat
sequences tied to decons, visits 1-18 in prop 10363, have been
moved
to the cycle 15 decon proposal xxxx for easier scheduling.} Note:
long-exposure
WFPC2 intflats must be scheduled during ACS anneals to
prevent
stray light from the WFPC2 lamps from contaminating long ACS
external
exposures.
WFPC2
11032
CTE
Extended Targets Closeout
Measuring
the charge transfer efficiency {CTE} of an astronomical CCD
camera
is crucial to determining the CCD's photometric fidelity across
the
field of view. WFPC2's CTE has degraded steadily over the last 13
years
because of continuous exposure to trapped particles in HST's
radiation
environment. The fraction of photometric signal lost from
WFPC2's
CTI {change transfer inefficiency} is a function of WFPC2's time
in
orbit, the integrated signal in the image, the location of the image
on
the CCD, and the background signal. Routine monitoring of WFPC2's
degrading
CTE over the last 13 years has primarily concerned the effects
of
CTI on point-source photometry. However, most of the sources imaged
by
WFPC2 are extended rather than point-like. This program aims to
characterize
the effects of CTI on the photometry and morphology of
extended
sources near the end of WFPC2's functional life. Images of a
standard
field within the rich galaxy cluster Abell 1689 are recorded
with
each WFPC2 camera using the F606W and F814W filters. These images
will
be compared with contemporaneous images of Abell 1689 recorded with
the
field rotated by approximately 180 degrees to assess differences
between
extended sources imaged near and far from the serial register.
The
images will also be compared with similar images recorded in Cycle 8
{Program
8456} to characterize the rate of CTE degradation over the
lifetime
of WFPC2.
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
11103
A
Snapshot Survey of The Most Massive Clusters of Galaxies
We
propose the continuation of our highly successful SNAPshot survey of
a
sample of 125 very X-ray luminous clusters in the redshift range
0.3-0.7.
As demonstrated by the 25 snapshots obtained so far in Cycle14
and
Cycle15 these systems frequently exhibit strong gravitational
lensing
as well as spectacular examples of violent galaxy interactions.
The
proposed observations will provide important constraints on the
cluster
mass distributions, the physical nature of galaxy-galaxy and
galaxy-gas
interactions in cluster cores, and a set of optically bright,
lensed
galaxies for further 8-10m spectroscopy. All of our primary
science
goals require only the detection and characterization of
high-surface-brightness
features and are thus achievable even at the
reduced
sensitivity of WFPC2. Because of their high redshift and thus
compact
angular scale our target clusters are less adversely affected by
the
smaller field of view of WFPC2 than more nearby systems.
Acknowledging
the broad community interest in this sample we waive our
data
rights for these observations. Due to a clerical error at STScI our
approved
Cycle15 SNAP program was barred from execution for 3 months and
only
6 observations have been performed to date - reinstating this SNAP
at
Cycle16 priority is of paramount importance to reach meaningful
statistics.
WFPC2
11134
WFPC2
Tidal Tail Survey: Probing Star Cluster Formation on the Edge
The
spectacular HST images of the interiors of merging galaxies such as
the
Antennae and NGC 7252 have revealed rich and diverse populations of
star
clusters created over the course of the interaction. Intriguingly,
our
WFPC2 study of tidal tails in these and other interacting pairs has
shown
that star cluster birth in the tails does not follow a similarly
straightforward
evolution. In fact, cluster formation in these
relatively
sparse environments is not guaranteed -- only one of six
tails
in our initial study showed evidence for a significant population
of
young star clusters. The tail environment thus offers the opportunity
to
probe star cluster formation on the edge of the physical parameter
space
{e.g., of stellar and gas mass, density, and pressure} that
permits
it to occur. We propose to significantly extend our pilot sample
of
optically bright, gas-rich tidal tails by a factor of 4 in number to
include
a more diverse population of tails, encompassing major and minor
mergers,
gas-rich and gas-poor tails, as well as early, late, and merged
interaction
stages. With 21 orbits of HST WFPC2 imaging in the F606W and
F814W
filters, we can identify, roughly age-date, and measure sizes of
star
clusters to determine what physical parameters affect star cluster
formation.
WFPC2 imaging has been used effectively in our initial study
of
four mergers, and it will be possible in this program to reach
similar
limits of Mv=-8.5 for each of 16 more tails. With the much
larger
sample we expect to isolate which factors, such as merger stage,
HI
content, and merger mass ratio, drive the formation of star clusters.
WFPC2
11361
Hubble
Heritage Observations of Mars at 2007 Opposition
We
will obtain images of Mars at opposition in December 2007.
FLIGHT
OPERATIONS SUMMARY:
Significant
Spacecraft Anomalies: (The following are preliminary reports
of
potential non-nominal performance that will be investigated.)
HSTARS:
11086
- GSaq(2,3,3) failed to RGA hold
At AOS 338/04:32:30 flags indicated that during LOS GSacq(2,3,3)
scheduled at 338/04:00:52 failed to RGA hold due to receiving stop
flag
QF2STOPF on FGS 2.
COMPLETED
OPS REQUEST: (None)
COMPLETED
OPS NOTES: (None)
SCHEDULED
SUCCESSFUL
FGS
GSacq 08
07
FGS
REacq
06
06
OBAD
with Maneuver
28
28
SIGNIFICANT
EVENTS: (None)