HUBBLE
SPACE TELESCOPE - Continuing to collect World Class Science
DAILY
REPORT # 4595
PERIOD
COVERED: UT April 22, 2008 (DOY 113)
OBSERVATIONS
SCHEDULED
ACS/SBC
11131
Star
formation at large radii in cooling flow brightest cluster galaxies
We
propose to take deep ACS FUV images of the bright central galaxies in
two
powerful cooling flow clusters for which we have VLT UBR images,
with
the object of determining whether the UV excesses we observe at
large
radii (>15kpc) are caused by young stars, ultrahot (WR) stars, or
an
as yet unknown source. Current models of excess UV light at the
AGN-dominated
centers of these galaxies cannot easily be extended to
large
radii. New understanding of star formation in these clusters will
be
directly applicable to scenarios of galaxy formation in the early
universe.
ACS/SBC
11151
Evaluating
the Role of Photoevaporation of Protoplanetary Disk Dispersal
Emission
produced by accretion onto the central star leads to
photoevaporation,
which may play a fundamental role in disk dispersal.
Models
of disk photoevaporation by the central star are challenged by
two
potential problems: the emission produced by accretion will be
substantially
weaker for low-mass stars, and photoevaporation must
continue
as accretion slows. Existing FUV spectra of CTTSs are biased to
solar-mass
stars with high accretion rates, and are therefore
insufficient
to address these problems. We propose use HST/ACS SBC
PR130L
to obtain FUV spectra of WTTSs and of CTTSs at low masses and
mass
accretion rates to provide crucial data to evaluate
photoevaporation
models. We will estimate the FUV and EUV luminosities
of
low-mass CTTSs with small mass accretion rates, CTTSs with transition
disks
and slowed accretion, and of magnetically-active WTTSs.
FGS
11210
The
Architecture of Exoplanetary Systems
Are
all planetary systems coplanar? Concordance cosmogony makes that
prediction.
It is, however, a prediction of extrasolar planetary system
architecture
as yet untested by direct observation for main sequence
stars
other than the Sun. To provide such a test, we propose to carry
out
FGS astrometric studies on four stars hosting seven companions. Our
understanding
of the planet formation process will grow as we match not
only
system architecture, but formed planet mass and true distance from
the
primary with host star characteristics for a wide variety of host
stars
and exoplanet masses. We propose that a series of FGS astrometric
observations
with demonstrated 1 millisecond of arc per-observation
precision
can establish the degree of coplanarity and component true
masses
for four extrasolar systems: HD 202206 {brown dwarf+planet}; HD
128311
{planet+planet}, HD 160691 = mu Arae {planet+planet}, and HD
222404AB
= gamma Cephei {planet+star}. In each case the companion is
identified
as such by assuming that the minimum mass is the actual mass.
For
the last target, a known stellar binary system, the companion orbit
is
stable only if coplanar with the AB binary orbit.
FGS
11211
An Astrometric
Calibration of Population II Distance Indicators
In
2002 HST produced a highly precise parallax for RR Lyrae. That
measurement
resulted in an absolute magnitude, M{V}= 0.61+/-0.11, a
useful
result, judged by the over ten refereed citations each year
since.
It is, however, unsatisfactory to have the direct,
parallax-based,
distance scale of Population II variables based on a
single
star. We propose, therefore, to obtain the parallaxes of four
additional
RR Lyrae stars and two Population II Cepheids, or
stars.
The Population II Cepheids lie with the RR Lyrae stars on a
common
K-band Period-Luminosity relation. Using these parallaxes to
inform
that relationship, we anticipate a zero-point error of 0.04
magnitude.
This result should greatly strengthen confidence in the
Population
II distance scale and increase our understanding of RR Lyrae
star
and Pop II Cepheid astrophysics.
NIC1/NIC2/NIC3
8795
NICMOS
Post-SAA calibration - CR Persistence Part 6
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 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.
NIC2
11219
Active
Galactic Nuclei in nearby galaxies: a new view of the origin of
the
radio-loud radio-quiet dichotomy?
Using
archival HST and Chandra observations of 34 nearby early-type
galaxies
{drawn from a complete radio selected sample} we have found
evidence
that the radio-loud/radio-quiet dichotomy is directly connected
to
the structure of the inner regions of their host galaxies in the
following
sense: [1] Radio-loud AGN are associated with galaxies with
shallow
cores in their light profiles [2] Radio-quiet AGN are only
hosted
by galaxies with steep cusps. Since the brightness profile is
determined
by the galaxy's evolution, through its merger history, our
results
suggest that the same process sets the AGN flavour. This
provides
us with a novel tool to explore the co-evolution of galaxies
and
supermassive black holes, and it opens a new path to understand the
origin
of the radio-loud/radio-quiet AGN dichotomy. Currently our
analysis
is statistically incomplete as the brightness profile is not
available
for 82 of the 116 targets. Most galaxies were not observed
with
HST, while in some cases the study is obstructed by the presence of
dust
features. We here propose to perform an infrared NICMOS snapshot
survey
of these 82 galaxies. This will enable us to i} test the reality
of
the dichotomic behaviour in a substantially larger sample; ii} extend
the
comparison between radio-loud and radio-quiet AGN to a larger range
of
luminosities.
WFPC2
11040
Geometric
Distortion / Astrometry Closeout
These
observations will serve as a final characterization of the
geometric
distortion and astrometric calibration. The Omega-Cen inner
calibration
field is used. Filters F300W, F555W, and F814W are observed
at
5 roll angles spanning 180 degrees; F218W is observed at a single
roll
angle.
WFPC2
11160
Escape
fraction and stellar populations in a highly magnified
Lyman-Break
Galaxy
Understanding
how star-forming galaxies contribute to cosmic
reionization
is one of the frontiers of observational cosmology. A key
ingredient
in this issue is measuring the escape fraction of
Lyman-continuum
photons in high redshift galaxies (z>3). Gravitationally
lensed
Lyman-break galaxies (LBGs) act as important laboratories for
studying
the resolved physical properties at sub-kpc scales with high
signal-to-noise.
Correlating the local escape fraction with physical
parameters
derived from stellar population modeling (such as the star
formation
rate, age and reddening) will offer new insights into
understanding
the physical processes involved with the production of
ionizing
photons. We propose here follow-up observations of the "Cosmic
Eye",
a remarkable, highly magnified (x 30), Lyman-break galaxy at
z~3.07
using WFPC2 and NICMOS. Deep ultraviolet WFPC2 imaging will
provide
a detailed study of variations in the escape fraction, while
WFPC2
and NICMOS/NIC2 imaging will complement the current broad-band
detections
to allow a precise modeling of the spatially-dependent
spectral
energy distribution. This will allow the first comprehensive
analysis
between the escape fraction, the local SED and the dynamics of
a
distant galaxy.
WFPC2
11232
Determination
of Angular Expansion Velocities in the Ring Nebula
The
Ring Nebula (NGC 6720) represents an important stage in the
evolution
of planetary nebulae, being large enough that it has entered
the
post fast-wind stage yet has not reached the late ballistic phase of
objects
like the Helix Nebula. Understanding this nebula well presents
the
opportunity to determine how nebulae transition from their creation
phase
into the form they have as their material enters the interstellar
medium.
A recent study based on ground-based spectroscopy has derived a
new
and accurate model for the Ring Nebula. A well defined
characteristic
of this model is that it predicts a tangential velocity
of
20 km/s whereas the application of its quite uncertain trigonometric
parallax
distance of 700 (+450/-200) pc with the angular expansion
velocity
determined from HST observations with a 2 year time base
indicates
a tangential velocity of 69 (+45/-20) km/s. This disagreement
indicates
that either the distance is even more uncertain than thought
or that
the earlier angular velocity is incorrect. We propose to make a
new
set of observations of the Ring Nebula in the diagnostic emission
line
filters F469N (HeII), F502N ([OIII]), and F658N ([NII]) that will
produce
much more accurate angular velocities than the previous study by
having
a time base of 8.8 years and imaging the nebula entirely within a
single
CCD of the WFPC2. The primary result from this study will be an
accurate
distance to this important nebula and from this to be able to
use
this object to refine our picture of how planetary nebulae evolve
during
middle-age.
WFPC2
11233
Multiple
Generations of Stars in Massive Galactic Globular Clusters
This
is a follow-up to recent HST imaging of NGC 2808, which discovered
that
its main sequence is triple, with three well-separated parallel
branches
{Fig.~1}. Along with the double MS of Omega Centauri, this
challenges
the long-held paradigm that globular clusters are simple,
single
stellar populations. The cause of this main sequence multiplicity
in
both clusters is likely to be differences in helium abundance, which
could
play a fundamental role in the understanding of stellar
populations.
We propose to image seven more of the most massive globular
clusters,
to examine their main sequences for indications of splitting.
FLIGHT
OPERATIONS SUMMARY:
Significant
Spacecraft Anomalies: (The following are preliminary reports
of
potential non-nominal performance that will be investigated.)
HSTARS:
11267
- GSAcq(1,2,1) failed to RGA Control while LOS
Upon acquisition of signal at 113/22:09:19 vehicle was in RGA
control,
GSAcq(1,2,1) scheduled for 113/21:46:03 failed to RGA control with
QF2STOPF and QSTOP flags set. No other flags were seen.
Post-acquisition
OBAD map at 21:54:07 had RSS error of 20.16 arcseconds.
COMPLETED
OPS REQUEST: (None)
COMPLETED
OPS NOTES: (None)
SCHEDULED
SUCCESSFUL
FGS
GSacq
09
08
FGS
REacq
06
06
OBAD
with Maneuver
30
30
SIGNIFICANT
EVENTS: (None)