HUBBLE SPACE TELESCOPE - Continuing to collect World Class
Science
DAILY REPORT #4825
PERIOD COVERED: 5am April 2 - 5am April 3, 2009 (DOY
092/0900z-093/0900z)
OBSERVATIONS SCHEDULED
FGS 11704
The Ages of Globular Clusters and the Population II
Distance Scale
Globular clusters are the oldest objects in the universe
whose age can
be accurately determined. The dominant error in globular
cluster age
determinations is the uncertain Population II distance
scale. We propose
to use FGS 1r to obtain parallaxes with an accuracy of 0.2
milliarcsecond for 9 main sequence stars with [Fe/H] <
-1.5. This will
determine the absolute magnitude of these stars with
accuracies of 0.04
to 0.06mag. This data will be used to determine the
distance to 24
metal-poor globular clusters using main sequence fitting.
These
distances (with errors of 0.05 mag) will be used to
determine the ages
of globular clusters using the luminosity of the subgiant
branch as an
age indicator. This will yield absolute ages with an
accuracy 5%, about
a factor of two improvement over current estimates.
Coupled with
existing parallaxes for more metal-rich stars, we will be
able to
accurately determine the age for globular clusters over a
wide range of
metallicities in order to study the early formation
history of the Milky
Way and provide an independent estimate of the age of the
universe.
The Hipparcos database contains only 1 star with [Fe/H]
< -1.4 and an
absolute magnitude error less than 0.18 mag which is
suitable for use in
main sequence fitting. Previous attempts at main sequence
fitting to
metal-poor globular clusters have had to rely on
theoretical
calibrations of the color of the main sequence. Our HST
parallax program
will remove this source of possible systematic error and
yield distances
to metal-poor globular clusters which are significantly
more accurate
than possible with the current parallax data. The HST
parallax data will
have errors which are 10 times smaller than the current
parallax data.
Using the HST parallaxes, we will obtain main sequence
fitting distances
to 11 globular clusters which contain over 500 RR Lyrae
stars. This will
allow us to calibrate the absolute magnitude of RR Lyrae
stars, a
commonly used Population II distance indicator.
WFPC2 11603
A Comprehensive Study of Dust Formation in Type II
Supernovae with HST,
Spitzer and Gemini
The recent discovery of three extremely bright Type II
SNe, (2007it,
2007oc, 2007od) gives us a unique opportunity to combine
observations
with HST, Spitzer and Gemini to study the little
understood dust
formation process in Type II SNe. Priority 1 Spitzer Cycle
5 and band 1
Gemini 2008A time has already been approved for this
project. Since
late-time Type II SNe are faint and tend to be in crowded
fields, we
need the high sensitivity and high spatial resolution of
ACS/HRC and
NICMOS/NIC2 for these observations. This project is
motivated by the
recent detection of large amounts of dust in high redshift
galaxies. The
dust in these high-z galaxies must come from young,
massive stars so
Type II SNe could be potential sources. The mechanism and
the efficiency
of dust condensation in Type II SN ejecta are not well
understood,
largely due to the lack of observational data. We plan to
produce a
unique dataset, combining spectroscopy and imaging in the
visible, near-
and mid-IR covering the key phase, 400-700 days after
maximum when dust
is known to form in the SN ejecta. Therefore, we are
proposing for
coordinated HST/NOAO observations (HST ACS/HRC,
NICMOS/NIC2 &
Gemini/GMOS and TReCS) which will be combined with our
Spitzer Cycle 5
data to study these new bright SNe. The results of this
program will
place strong constraints on the formation of dust seen in
young high
redshift (z>5) galaxies.
WFPC2 11797
Supplemental WFPC2 CYCLE 16 Intflat Linearity Check and
Filter Rotation
Anomaly Monitor
Supplemental observations to 11029, to cover period from
Aug 08 to SM4.
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 11022 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.
Note: These are supplemental observations to cover June to
SM4 (Oct 8
'08) + 6 months.
WFPC2 11974
High-resolution Imaging for 9 Very Bright,
Spectroscopically Confirmed,
Group-scale Lenses
There are large samples of strong lenses that probe small
(galaxy) scale
masses (e.g., SLACS, SQLS, COSMOS). There are also large
samples of
strong lenses that probe large (rich cluster) scale masses
(e.g.,
various rich Abell clusters, the Hennawi et al. 2008 SDSS
sample). The
sample of strong lenses that probe intermediate
(group/cluster-core)
scale masses, however, is sparse, and so any significant
additions to
this sample are important. Here we present a sample of
strong lenses
that not only probe these intermediate scales but are also
quite bright,
since the sample is based almost entirely upon data from
the SDSS, a
relatively shallow and poor-resolution survey, at least in
comparison to
most other strong lens hunting grounds, such as COSMOS and
CFHTLS. What
we lack are the high-resolution imaging data needed to
construct
detailed lensing models, to probe the mass and light
profiles of the
lensing galaxies and their environments, and to
characterize the
morphologies of the lensed (source) galaxies. Only HST can
provide these
data, and so we are proposing here for 81 orbits of deep
WFPC2 F450W,
F606W and F814W imaging, for 9 of our best and brightest
intermediate-scale lensing systems with known
spectroscopic redshifts
and with Einstein radii between 4 and 8 arcsec.
WFPC2 11975
UV Light from Old Stellar Populations: a Census of UV
Sources in
Galactic Globular Clusters
In spite of the fact that HST has been the only operative
high-resolution eye in the UV-window over the last 18
years, no
homogeneous UV survey of Galactic globular clusters (GGCs)
has been
performed to date. In order to fill this gap in the
stellar population
studies, we propose a program that exploits the unique
capability of the
WFPC2 and the SBC in the far-/mid- UV for securing deep UV
imaging of 46
GGCs. The proposed observations will allow to study with
unprecedented
accuracy the hottest GGC stars, comprising the extreme
horizontal branch
(HB) stars and their progeny (the so-called AGB-manque',
and Post-early
AGB stars), and "exotic stellar populations"
like the blue straggler
stars and the interacting binaries. The targets have been
selected to
properly sample the GGC metallicity/structural parameter
space, thus to
unveil any possible correlation between the properties of
the hot
stellar populations and the cluster characteristics. In
addition, most
of the targets have extended HB "blue tails",
that can be properly
studied only by means of deep UV observations, especially
in the far-UV
filters like the F160BW, that is not foreseen on the WFC3.
This data
base is complemented with GALEX observations in the
cluster outermost
regions, thus allowing to investigate any possible trend
of the
UV-bright stellar types over the entire radial extension
of the
clusters. Although the hottest GGC stars are just a small
class of
"special" objects, their study has a broad
relevance in the context of
structure formation and chemical evolution in the early
Universe,
bringing precious information on the basic star formation
processes and
the origin of blue light from galaxies. Indeed, the
proposed
observations will provide the community with an
unprecedented data set
suitable for addressing a number of still open
astrophysical questions,
ranging from the main drivers of the HB morphology and the
mass loss
processes, to the origin of the UV upturn in elliptical
galaxies, the
dating of distant systems from integrated light, and the
complex
interplay between stellar evolution and dynamics in dense
stellar
aggregates. In the spirit of constructing a community
resource, we
entirely waive the proprietary period for these
observations.
FLIGHT OPERATIONS SUMMARY:
Significant Spacecraft Anomalies: (The following are
preliminary reports
of potential non-nominal performance that will be
investigated.)
HSTARS:
11759 - GSAcq (1,2,1) scheduled at 092/12:48:25z and REAcq
(1,2,1) scheduled at
092/14:21:50z both failed with QF1STOPF and QSTOP flags set.
Observations affected: WFPC 109-120, Proposal ID# 11603.
11761 - REAcq (1,2,2) scheduled at 092/22:41:12z failed at
092/22:45:38z
due to FGS Sequential Attitude update being too large to correct.
Observations affected: WFPC 127-129, proposal ID# 11975.
11762 - REAcq (1,2,2) scheduled from 093/03:40:52z -
03:48:20 failed due to
FGS Sequential Attitude update being too large to correct.
Observations affected: WFPC 137-138, Proposal ID# 11975.
COMPLETED OPS REQUEST: (None)
COMPLETED OPS NOTES: (None)
SCHEDULED
SUCCESSFUL
FGS
GSAcq
05
04
FGS REAcq
07
04
OBAD with Maneuver 22
22
SIGNIFICANT EVENTS: (None)