HUBBLE
SPACE TELESCOPE - Continuing to Collect World Class Science
DAILY
REPORT #5044
PERIOD
COVERED: 5am March 2 - 5am March 3, 2010 (DOY 061/10:00z-062/10:00z)
OBSERVATIONS
SCHEDULED
ACS/SBC/COS/NUV/FUV
11579
The
Difference Between Neutral- and Ionized-Gas Metal Abundances in
Local
Star-Forming Galaxies with COS
The
metallicity of galaxies and its evolution with redshift is of
paramount
importance for understanding galaxy formation. Abundances in
the
interstellar medium (ISM) are typically determined using
emission-line
spectroscopy of HII regions. However, since HII regions
are
associated with recent SF they may not have abundances typical for
the
galaxy as a whole. This is true in particular for star-forming
galaxies
(SFGs), in which the bulk of the metals may be contained in the
neutral
gas. It is therefore important to directly probe the metal
abundances
in the neutral gas. This can be done using absorption lines
in
the Far UV. We have developed techniques to do this in SFGs, where
the
absorption is measured for sightlines toward bright SF regions
within
the galaxy itself. We have successfully applied this technique to
a
sample of galaxies observed with FUSE. The results have been very
promising,
suggesting in I Zw 18 that abundances in the neutral gas may
be
up to 0.5 dex lower than in the ionized gas. However, the
interpretation
of the FUSE data is complicated by the very large FUSE
aperture
(30 arcsec), the modest S/N, and the limited selection of
species
available in the FUSE bandpass. The advent of COS on HST now
allows
a significant advance in all of these areas. We will therefore
obtain
absorption line spectroscopy with G130M in the same sample for
which
we already have crude constraints from FUSE. We will obtain
ACS/SBC
images to select the few optimal sightlines to target in each
galaxy.
The results will be interpreted through line-profile fitting to
determine
the metal abundances constrained by the available lines. The
results
will provide important new insights into the metallicities of
galaxies,
and into outstanding problems at high redshift such as the
observed
offset between the metallicities of Lyman Break Galaxies and
Damped
Lyman Alpha systems.
ACS/WFC
11558
Planetary
Nebulae, Globular Clusters and Binary Mergers
Four
planetary nebulae (PNe) have been found within 130 of the 150
globular
clusters (GCs) of our Galaxy. This might not seem like many,
but
stellar evolution predicts that the old populations of these
clusters
should contain no PN at all! Observations of three of the four
GC
PNe show them to have peculiar characteristics, possibly indicative
of
a binary/merger origin. In particular two of the three observed GC
PNe
have masses which correspond to main sequence masses ~2-3 times the
clusters'
turn-off masses, suggesting mergers of two, or even three stars
have
taken place. One of the three observed PNe is H-deficient, a
characteristic
exhibited by only 5 out of hundreds of field PNe.
H-deficient
PNe have been associated with binarity. As usual, not all
parameters
for these three PNe are clean indications of their binary
origin.
In an approved cycle 15 ACS/WFI proposal we asked to obtain
observations
of the only GC PN that has never been observed before at
high
resolution and whose central star has never been detected, as well
as
of the one H-deficient GC PN for which only low-quality WFPC2 images
exist.
When ACS stopped working we moved part of the observations to
WFPC2.
With this proposal we ask to complete our project, by obtaining
two
ACS/WFI images that could not be efficiently taken with WFPC2. These
objects
could tip the balance toward a binary interpretation for the GC
PNe
or make us seriously reconsider our understanding of stellar
evolution
in old populations.
COS/FUV
11895
FUV
Detector Dark Monitor
The
purpose of this proposal is to monitor the FUV detector dark rate by
taking
long science exposures without illuminating the detector. The
detector
dark rate and spatial distribution of counts will be compared
to
pre-launch and SMOV data in order to verify the nominal operation of
the
detector. Variations of count rate as a function of orbital position
will
be analyzed to find dependence of dark rate on proximity to the
SAA.
Dependence of dark rate as function of time will also be tracked.
COS/FUV
11897
FUV
Spectroscopic Sensitivity Monitoring
The
purpose of this proposal is to monitor sensitivity in each FUV
grating
mode to detect any changes due to contamination or other causes.
STIS/CC
11571
A
Fundamental Test of Accretion Physics with NGC 4203
The
rapid evolution of quasars indicates that supermassive black holes
in
galaxy nuclei spend most of their time in a relatively quiescent
state.
Studies of nearby galaxies demonstrate that many such black holes
are
accreting at a low rate, and appear as low-luminosity active
galactic
nuclei (LLAGNs). Theoretical arguments suggest that the mode of
accretion
onto a central black hole may be very different in LLAGNs as
compared
to high-luminosity systems. The LINER NGC 4203 provides an
excellent
opportunity to investigate quantitatively the accretion
process
in a LLAGN, and hence the typical accretion state for a
supermassive
black hole. Cycle 7 STIS data acquired at one position
angle
reveal double-peaked H-alpha emission in the nucleus that may
trace
an accretion disk, and spatially resolved emission that places an
upper
limit on black-hole mass. We propose observations with STIS to map
the
two-dimensional velocity field of the circumnuclear gas disk in the
central
regions of NGC 4203, in order to measure the black-hole mass.
This
parameter is essential for testing theoretical models of accretion,
determining
the mass accretion rate, and estimating the radiative
efficiency
for accreted matter. The results will be important for making
sense
of LLAGNs, and for translating their measured luminosity into
accretion
rates that trace the growth of black holes. This is a
resubmission
of a proposal that was approved for 5 orbits in Cycle 13
(GO-10191)
but never carried out due to the failure of STIS.
STIS/CCD
11844
CCD
Dark Monitor Part 1
The
purpose of this proposal is to monitor the darks for the STIS CCD.
STIS/CCD
11846
CCD
Bias Monitor-Part 1
The
purpose of this proposal is to monitor the bias in the 1x1, 1x2,
2x1,
and 2x2 bin settings at gain=1, and 1x1 at gain = 4, to build up
high-S/N
superbiases and track the evolution of hot columns.
STIS/CCD/MA2
11568
A
SNAPSHOT Survey of the Local Interstellar Medium: New NUV Observations
of
Stars with Archived FUV Observations
We
propose to obtain high-resolution STIS E230H SNAP observations of
MgII
and FeII interstellar absorption lines toward stars within 100
parsecs
that already have moderate or high-resolution far-UV (FUV),
900-1700
A, observations available in the MAST Archive. Fundamental
properties,
such as temperature, turbulence, ionization, abundances, and
depletions
of gas in the local interstellar medium (LISM) can be
measured
by coupling such observations. Due to the wide spectral range
of
STIS, observations to study nearby stars also contain important data
about
the LISM embedded within their spectra. However, unlocking this
information
from the intrinsically broad and often saturated FUV
absorption
lines of low-mass ions, (DI, CII, NI, OI), requires first
understanding
the kinematic structure of the gas along the line of
sight.
This can be achieved with high resolution spectra of high-mass
ions,
(FeII, MgII), which have narrow absorption lines, and can resolve
each
individual velocity component (interstellar cloud). By obtaining
short
(~10 minute) E230H observations of FeII and MgII, for stars that
already
have moderate or high- resolution FUV spectra, we can increase
the
sample of LISM measurements, and thereby expand our knowledge of the
physical
properties of the gas in our galactic neighborhood. STIS is the
only
instrument capable of obtaining the required high resolution data
now
or in the foreseeable future.
WFC3/IR
11915
IR
Internal Flat Fields
This
program is the same as 11433 (SMOV) and depends on the completion
of
the IR initial alignment (Program 11425). This version contains three
instances
of 37 internal orbits: to be scheduled early, middle, and near
the
end of Cycle 17, in order to use the entire 110-orbit allocation.
In
this test, we will study the stability and structure of the IR
channel
flat field images through all filter elements in the WFC3-IR
channel.
Flats will be monitored, i.e. to capture any temporal trends in
the
flat fields and delta flats produced. High signal observations will
provide
a map of the pixel-to-pixel flat field structure, as well as
identify
the positions of any dust particles.
WFC3/UVIS
11908
Cycle
17: UVIS Bowtie Monitor
Ground
testing revealed an intermittent hysteresis type effect in the
UVIS
detector (both CCDs) at the level of ~1%, lasting hours to days.
Initially
found via an unexpected bowtie-shaped feature in flatfield
ratios,
subsequent lab tests on similar e2v devices have since shown
that
it is also present as simply an overall offset across the entire
CCD,
i.e., a QE offset without any discernable pattern. These lab tests
have
further revealed that overexposing the detector to count levels
several
times full well fills the traps and effectively neutralizes the
bowtie.
Each visit in this proposal acquires a set of three 3x3 binned
internal
flatfields: the first unsaturated image will be used to detect
any
bowtie, the second, highly exposed image will neutralize the bowtie
if
it is present, and the final image will allow for verification that
the
bowtie is gone.
WFC3/UVIS
12018
Ultra-Luminous
X-Ray Sources in the Most Metal-Poor Galaxies
There
is growing observational and theoretical evidence to suggest that
Ultra-Luminous
X-ray sources (ULX) form preferentially in low
metallicity
environments. Here we propose a survey of 27 nearby (<
30Mpc)
star-forming Extremely Metal Poor Galaxies (Z<5% solar). There
are
almost no X-ray observations of such low abundance galaxies (3 in
the
Chandra archive). These are the most metal-deficient galaxies known,
and
a logical place to find ULX if they favor metal-poor systems. We
plan
to test recent population synthesis models which predict that ULX
should
be very numerous in metal-poor galaxies. We will also test the
hypothesis
that ULX form in massive young star clusters, and ask for HST
time
to obtain the necessary imaging data.
WFC3/UVIS/IR
11909
UVIS
Hot Pixel Anneal
The
on-orbit radiation environment of WFC3 will continually generate new
hot
pixels. This proposal performs the procedure required for repairing
those
hot pixels in the UVIS CCDs. During an anneal, the two-stage
thermo-electric
cooler (TEC) is turned off and the four-stage TEC is
used
as a heater to bring the UVIS CCDs up to ~20 deg. C. As a result of
the
CCD warmup, a majority of the hot pixels will be fixed; previous
instruments
such as WFPC2 and ACS have seen repair rates of about 80%.
Internal
UVIS exposures are taken before and after each anneal, to allow
an
assessment of the procedure's effectiveness in WFC3, provide a check
of
bias, global dark current, and hot pixel levels, as well as support
hysteresis
(bowtie) monitoring and CDBS reference file generation. One
IR
dark is taken after each anneal, to provide a check of the IR
detector.
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
07
07
FGS
REAcq
09
09
OBAD
with Maneuver 05
05
SIGNIFICANT
EVENTS: (None)