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 # 4432
PERIOD
COVERED: UT August 22, 2007 (DOY 234)
OBSERVATIONS
SCHEDULED
WFPC2
10787
Modes
of Star Formation and Nuclear Activity in an Early Universe
Laboratory
Nearby
compact galaxy groups are uniquely suited to exploring the
mechanisms
of star formation amid repeated and ongoing gravitational
encounters,
conditions similar to those of the high redshift universe.
These
dense groups host a variety of modes of star formation, and they
enable
fresh insights into the role of gas in galaxy evolution. With
Spitzer
mid-IR observations in hand, we have begun to obtain high
quality,
multi-wavelength data for a well- defined sample of 12 nearby
{<4500km/s}
compact groups covering the full range of evolutionary
stages.
Here we propose to obtain sensitive BVI images with the ACS/WFC,
deep
enough to reach the turnover of the globular cluster luminosity
function,
and WFPC2 U-band and ACS H-alpha images of Spitzer-identified
regions
hosting the most recent star formation. In total, we expect to
detect
over 1000 young star clusters forming inside and outside
galaxies,
more than 4000 old globular clusters in >40 giant galaxies
{including
16 early-type galaxies}, over 20 tidal features,
approximately
15 AGNs, and intragroup gas in most of the 12 groups.
Combining
the proposed ACS images with Chandra observations, UV GALEX
observations,
ground-based H-alpha imaging, and HI data, we will conduct
a
detailed study of stellar nurseries, dust, gas kinematics, and AGN.
NIC1
11304
The
L/T Transition in the Photospheres of Young Sub-Stellar Companions
We
propose 3.6-8.0 micron IRAC photometry and 5.5?22 micron
low-resolution
IRS spectroscopy and imaging of the sub-stellar
companions
to the ~0.3 Gyr old stars HN Peg and HD 203030. The spectral
types
of the two secondaries span the critical transition between L and
T
dwarfs, which is characterized by a rapid sedimentation of dust and
appearance
of methane in sub-stellar photospheres. HN Peg B {T2.5} and
HD
203030 B {L7.5} are the youngest known brown dwarfs at this
transition,
and present a unique opportunity to examine the role of
surface
gravity in the process. Both objects stand out from 1-10 Gyr L/T
transition
dwarfs in the field because they are underluminous in the
near-
IR compared to the expected luminosities for their ages. Probable
reasons
include: {1} a decrease in the effective temperature at the
onset
of methane formation at lower surface gravities in sub-stellar
photospheres,
or {2} a shift in the emitted flux from the near-IR to the
mid-IR
region of the SED of young brown dwarfs. The mid-IR is key for
distinguishing
between these two hypotheses because it contains several
fundamental
molecular transitions that create deep absorption bands in
the
SEDs of L and T dwarfs, and that are inaccessible for study from the
ground.
Our existing IRAC photometry of HN Peg B does reveal a 0.3-0.5
mag
excess in its 3.6-8.0 micron SED. However, this excess is
insufficient
to account for the lower luminosity of HN Peg B, and
indicates
that both of the above hypotheses may hold true to certain
degrees.
With the present proposal we aim to independently confirm the
gravity-dependent
behavior of L/T transition photospheres in the mid-IR
through
IRAC photometry of HD 203030 B. We will also seek the culprit
for
the mid- IR excess of HN Peg B through low resolution spectroscopy
and
peak-up imaging with IRS. To check for possible duplicity of HN Peg
B
as the reason for its excess, we request high angular resolution
imaging
with HST to complement our lower resolution Spitzer imaging.
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.
WFPC2
11031
CTE
Background Dependence 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 {charge 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 CTE
over
the last 13 years permits an assessment of all but the last
condition.
The dependence of CTE on background signal must be
characterized,
however, because a large fraction of WFPC2 images have
been
obtained under conditions of significant sky background. This
program
aims to assess the end-of-life CTE of WFPC2's CCDs separately as
a
function of background signal. Traditional images of an off-center
field
in NGC 5139 {Omega Cen} are recorded after preflashing {or before
postflashing}
the CCDs with internal lamps to provide average background
signals
of 0-160 e-, which span the range of sky backgrounds observed in
~99%
of long-exposure narrow- and broad-band WFPC2 images.
WFPC2
11176
Location
and the Origin of Short Gamma-Ray Bursts
During
the past decade extraordinary progress has been made in
determining
the origin of long-duration gamma-ray bursts. It has been
conclusively
shown that these objects derive from the deaths of massive
stars.
Nonetheless, the origin of their observational cousins,
short-duration
gamma-ray bursts {SGRBs} remains a mystery. While SGRBs
are
widely thought to result from the inspiral of compact binaries, this
is
a conjecture. A number of hosts of SGRBs have been identified, and
have
been used by some to argue that SGRBs derive primarily from an
ancient
population {~ 5 Gyr}; however, it is not known whether this
conclusion
more accurately reflects selection biases or astrophysics.
Here
we propose to employ a variant of a technique that we pioneered and
used
to great effect in elucidating the origins of long-duration bursts.
We
will examine the degree to which SGRB locations trace the red or blue
light
of their hosts, and thus old or young stellar populations. This
approach
will allow us to study the demographics of the SGRB population
in
a manner largely free of the distance dependent selection effects
which
have so far bedeviled this field, and should give direct insight
into
the age of the SGRB progenitor population.
FLIGHT
OPERATIONS SUMMARY:
Significant
Spacecraft Anomalies: (The following are preliminary reports
of
potential non-nominal performance that will be investigated.)
HSTARS:
10953
- GSAcq (1,2,1) failed to RGA Hold
GSAcq (1,2,1) scheduled from 235/07:46:05-07:53:32 failed to RGA
Hold
due to QSTOP flag on FGS 1.
OBAD #1: V1 69.79, V2 -1843.49, V3 63.91, RSS 1845.92
OBAD #2: V1 -8.78, V2 4.49, V3 6.40, RSS 11.76
At AOS 235/08:55:19 OBAD MAP: V1 -51.55, V2 -823.28, V3 -35.36,
RSS 825.65
COMPLETED
OPS REQUEST: (None)
COMPLETED
OPS NOTES: (None)
SCHEDULED
SUCCESSFUL
FGS
GSacq
06
05
FGS
REacq
08
08
OBAD
with Maneuver
28
28
SIGNIFICANT
EVENTS: (None)