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Daily Report #5121



 
 
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Old June 21st 10, 03:02 PM posted to sci.astro.hubble
Cooper, Joe
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Posts: 568
Default Daily Report #5121

HUBBLE SPACE TELESCOPE - Continuing to Collect World Class Science

DAILY REPORT #5121

PERIOD COVERED: 5am June 18 - 5am June 21, 2010 (DOY 169/09:00z-172/09:00z)

FLIGHT OPERATIONS SUMMARY:

Significant Spacecraft Anomalies: (The following are preliminary
reports of potential non-nominal performance that will be
investigated.)

HSTARS:

12308 - GSAcq(1,2,1) at 169/23:17:55z acquired fine lock backup on FGS
1 following scan step limit exceeded on FGS 1.

Observations possibly affected: ACS 52, proposal ID#11593.


COMPLETED OPS REQUEST: (None)

COMPLETED OPS NOTES: (None)

SCHEDULED SUCCESSFUL
FGS GSAcq 24 24
FGS REAcq 23 23
OBAD with Maneuver 18 18

SIGNIFICANT EVENTS: (None)



OBSERVATIONS SCHEDULED:

ACS/WFC 11995

CCD Daily Monitor (Part 2)

This program comprises basic tests for measuring the read noise and
dark current of the ACS WFC and for tracking the growth of hot pixels.
The recorded frames are used to create bias and dark reference images
for science data reduction and calibration. This program will be
executed four days per week (Mon, Wed, Fri, Sun) for the duration of
Cycle 17. To facilitate scheduling, this program is split into three
proposals. This proposal covers 320 orbits (20 weeks) from 1 February
2010 to 20 June 2010.

WFC3/IR/S/C 11929

IR Dark Current Monitor

Analyses of ground test data showed that dark current signals are more
reliably removed from science data using darks taken with the same
exposure sequences as the science data, than with a single dark
current image scaled by desired exposure time. Therefore, dark current
images must be collected using all sample sequences that will be used
in science observations. These observations will be used to monitor
changes in the dark current of the WFC3-IR channel on a day-to-day
basis, and to build calibration dark current ramps for each of the
sample sequences to be used by Gos in Cycle 17. For each sample
sequence/array size combination, a median ramp will be created and
delivered to the calibration database system (CDBS).

WFC3/UVIS 11924

WFC3/UVIS External and Internal CTE Monitor

CCD detector Charge Transfer Inefficiency (CTI)-induced losses in
photometry and astrometry will be measured using observations of the
rich open cluster NGC6791 and with the EPER (Extended Pixel Edge
Response) method using tungsten lamp flat field exposures. Although we
do not expect to see CTE effects at the outset of Cycle 17, this CTE
monitoring program is the first of a multi-cycle program to monitor
and establish CTE-induced losses with time. We expect to measure CTE
effects with a precision comparable to the ACS measurements.

WFC3/UVIS 11912

UVIS Internal Flats

This proposal will be used to assess the stability of the flat field
structure for the UVIS detector throughout the 15 months of Cycle 17.
The data will be used to generate on-orbit updates for the delta-flat
field reference files used in the WFC3 calibration pipeline, if
significant changes in the flat structure are seen.

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 11907

UVIS Cycle 17 Contamination Monitor

The UV throughput of WFC3 during Cycle 17 is monitored via weekly
standard star observations in a subset of key filters covering
200-600nm and F606W, F814W as controls on the red end. The data will
provide a measure of throughput levels as a function of time and
wavelength, allowing for detection of the presence of possible
contaminants.

WFC3/UVIS 11905

WFC3 UVIS CCD Daily Monitor

The behavior of the WFC3 UVIS CCD will be monitored daily with a set
of full-frame, four-amp bias and dark frames. A smaller set of 2Kx4K
subarray biases are acquired at less frequent intervals throughout the
cycle to support subarray science observations. The internals from
this proposal, along with those from the anneal procedure (Proposal
11909), will be used to generate the necessary superbias and superdark
reference files for the calibration pipeline (CDBS).

STIS/CC 11847

CCD Bias Monitor-Part 2

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/CC 11845

CCD Dark Monitor Part 2

Monitor the darks for the STIS CCD.

COS/NUV/FUV 11742

Probing HeII Reionization with GALEX-selected Quasar Sightlines and
HST/COS

We propose spectroscopic observations with COS of eight z~3 QSOs that
we found to be bright in the far ultraviolet. Our aim is to study
intergalactic absorption caused by the onset of the He II Lyman
forest. Several lines of evidence suggest that helium reionization
occurred at z~3. Understanding this process is critical for a complete
picture of the intergalactic medium and its evolution; it also gives
clues to hydrogen reionization at z6. The only direct means of
assessing He II reionization is through far-UV observations of the He
II Lyman alpha forest. Only 6 sightlines are known to date where this
is feasible, despite extensive surveys. Our program is designed to
double the number of available sightlines. To this effect, we
cross-correlated all known z2.73 quasars with UV source lists from
the GALEX satellite. The selected quasars were all significantly
detected in the far UV by GALEX, and their UV colors are similar to
those of already known quasars with transparent sightlines. Spectra
obtained with COS will allow us to compile the first comprehensive
sample of He II absorption spectra probing similar redshifts, enabling
a systematic investigation of the He II reionization epoch and the
spectral shape of the UV background.

COS/NUV/FUV 11720

Detailed Analysis of Carbon Atmosphere White Dwarfs

We propose to obtain UV spectra for the newly discovered white dwarf
stars with a carbon- dominated atmosphere. Model calculations show
that these stars emit most of their light in the UV part of the
electromagnetic spectrum and that an accurate determination of the
flux in this region is crucial for an accurate determination of the
atmospheric parameters. It will also provide a unique opportunity to
test the atomic data and broadening theory in stellar conditions never
met before. This will play a primordial role in our path to understand
the origin of these objects as well to obtain a better understanding
of the evolution of stars in general. The principal objective we hope
to achieve with these observations are 1) obtain accurate surface
gravity/mass for these stars, 2) constrain/determine the abundance of
other elements (O, He, Mg, Ne etc.), especially oxygen, 3) verify the
accuracy of the various theoretical atomic data used in the model
calculations, 4) understand the origin and evolution of carbon
atmosphere white dwarfs, in particular whether progenitor stars as
massive as 10.5 solar masses can produce white dwarfs, rather than
supernovae. We propose to observe 5 objects chosen carefully to cover
the range of observed properties among carbon atmosphere white dwarfs
(effective temperature, surface gravity, abundance of hydrogen/helium
and magnetic field).

WFC3/IR 11708

Determining the Sub-stellar IMF in the Most Massive Young Milky Way
Cluster, Westerlund 1

Despite over 50 years of active research, a key question in galactic
astronomy remains unanswered: is the initial mass function (IMF) of
stars and sub-stellar objects universal, or does it depend on initial
conditions? The answer has profound consequences for the evolution of
galaxies as well as a predictive theory of star formation. Work to
date suggests that certain environments (high densities, e.g.
Elmegreen 2004; low metallicity, e.g. Larson 2005) should produce a
top-heavy IMF, and there are hints from unresolved star-bursts that
this might be the case. Yet, there is no clear evidence for an IMF
that differs from that characterizing the Galactic field stars in a
resolved stellar population down to one solar mass. Westerlund 1 is
the most massive young star cluster known in the Milky Way. With an
estimated mass of 5x10^4 Msun, an age of 3-5 Myr, and located at a
distance of 3-4 kpc, it presents a unique opportunity to test whether
the IMF in such a cluster deviates from the norm well down into the
brown dwarf regime. We propose WFC3 near-IR imaging to probe the IMF
down to 40 Jupiter masses. The data will enable use to: 1) provide a
stringent test of the universality of the IMF under conditions
approximating those of star-bursts; 2) search for primordial or
dynamic mass segregation in the clusters; and 3) assess whether the
cluster is likely to remain bound (as a massive open cluster) or
disperse into the field. We will obtain images in the F125W, F160W,
and F139M filters. The F139M filter covers a strong water absorption
feature and the color F125W/F139M is a powerful temperature diagnostic
in the range 2800-4000 K. This information will enable us to: a)
confirm membership for low mass stars suspected on the basis of their
position in the color-magnitude diagram; b) place the members in the
HR diagram; and c) estimate the masses and ages of cluster members for
low-mass stars and sub-stellar objects. This new capability offered
with the WFC3 (through a novel combination of filter complement, high
spatial resolution, and large field of view) will enable us to make a
fundamental test of whether the IMF is universal on a unique resolved
stellar population, as well as assess the clusters structure,
dynamics, and ultimate fate.

WFC3/UVIS/IR 11702

Search for Very High-z Galaxies with WFC3 Pure Parallel

WFC3 will provide an unprecedented probe to the early universe beyond
the current redshift frontier. Here we propose a pure parallel program
using this new instrument to search for Lyman-break galaxies at
6.5z8.8 and to probe the epoch of reionization, a hallmark event in
the history of the early universe. We request 200 orbits, spreading
over 30 ~ 50 high Galactic latitude visits (|b|20deg) that last for 4
orbits and longer, resulting a total survey area of about 140~230
square arcminute. Based on our understanding of the new HST parallel
observation scheduling process, we believe that the total number of
long-duration pure parallel visits in Cycle 17 should be sufficient to
accommodate our program. We waive all proprietary rights to our data,
and will also make the enhanced data products public in a timely
manner.

(1) We will use both the UVIS and the IR channels, and do not need to
seek optical data from elsewhere.

(2) Our program will likely triple the size of the probable candidate
samples at z~7 and z~8, and will complement other targeted programs
aiming at the similar redshift range.

(3) Being a pure parallel program, our survey will only make very
limited demand on the scarce HST resources. More importantly, as the
pure parallel pointings will be at random sight-lines, our program
will be least affected by the bias due to the large scale structure
("cosmic variance").

(4) We aim at the most luminous LBG population, and will address the
bright-end of the luminosity function at z~8 and z~7. We will
constrain the value of L* in particular, which is critical for
understanding the star formation process and the stellar mass assembly
history in the first few hundred million years of the universe.

(5) The candidates from our survey, most of which will be the
brightest ones that any surveys would be able to find, will have the
best chance to be spectroscopically confirmed at the current 8--10m
telescopes.

(6) We will also find a large number of extremely red, old galaxies at
intermediate redshifts, and the fine spatial resolution offered by the
WFC3 will enable us constrain their formation history based on the
study of their morphology, and hence shed light on their connection to
the very early galaxies in the universe.

COS/NUV/FUV 11698

The Structure and Dynamics of Virgo's Multi-Phase Intracluster Medium

The dynamical flows of the intracluster medium (ICM) are largely
unknown. We propose to map the spatial and kinematic distribution of
the warm ICM of the nearby Virgo cluster using the Cosmic Origins
Spectrograph. 15 sightlines at a range of impact parameters within the
virial radius of the cluster (0.2 - 1.7 Mpc) will be probed for
Lyman-alpha absorption and the data compared to blind HI, dust and
x-ray surveys to create a multi-phase map of the cluster's ICM.
Absorption line sightlines are commonly 40-100 kpc from a galaxy,
allowing the flow of baryons between galaxies and the ICM to be
assessed. The velocity distribution of the absorbers will be directly
compared to simulations and used to constrain the turbulent motions of
the ICM. This proposal will result in the first map of a cluster's
warm ICM and provide important tests for our theoretical understanding
of cluster formation and the treatment of gas cooling in cosmological
simulations.

WFC3/IR 11696

Infrared Survey of Star Formation Across Cosmic Time

We propose to use the unique power of WFC3 slitless spectroscopy to
measure the evolution of cosmic star formation from the end of the
reionization epoch at z6 to the close of the galaxy- building era at
z~0.3.Pure parallel observations with the grisms have proven to be
efficient for identifying line emission from galaxies across a broad
range of redshifts. The G102 grism on WFC3 was designed to extend this
capability to search for Ly-alpha emission from the first galaxies.
Using up to 250 orbits of pure parallel WFC3 spectroscopy, we will
observe about 40 deep (4-5 orbit) fields with the combination of G102
and G141, and about 20 shallow (2-3 orbit) fields with G141 alone.

Our primary science goals at the highest redshifts a (1) Detect Lya
in ~100 galaxies with z5.6 and measure the evolution of the Lya
luminosity function, independent of of cosmic variance; 2) Determine
the connection between emission line selected and continuum-break
selected galaxies at these high redshifts, and 3) Search for the
proposed signature of neutral hydrogen absorption at re-ionization. At
intermediate redshifts we will (4) Detect more than 1000 galaxies in
Halpha at 0.5z1.8 to measure the evolution of the
extinction-corrected star formation density across the peak epoch of
star formation. This is over an order-of-magnitude improvement in the
current statistics, from the NICMOS Parallel grism survey. (5) Trace
``cosmic downsizing" from 0.5z2.2; and (6) Estimate the evolution in
reddening and metallicty in star- forming galaxies and measure the
evolution of the Seyfert population. For hundreds of spectra we will
be able to measure one or even two line pair ratios -- in particular,
the Balmer decrement and [OII]/[OIII] are sensitive to gas reddening
and metallicity. As a bonus, the G102 grism offers the possibility of
detecting Lya emission at z=7-8.8.

To identify single-line Lya emitters, we will exploit the wide
0.8--1.9um wavelength coverage of the combined G102+G141 spectra. All
[OII] and [OIII] interlopers detected in G102 will be reliably
separated from true LAEs by the detection of at least one strong line
in the G141 spectrum, without the need for any ancillary data. We
waive all proprietary rights to our data and will make high-level data
products available through the ST/ECF.

COS/FUV 11687

SNAPing Coronal Iron

This is a Snapshot Survey to explore two forbidden lines of highly
ionized iron in late-type coronal sources. Fe XII 1349 (T~ 2 MK) and
Fe XXI 1354 (T~ 10 MK) -- well known to Solar Physics -- have been
detected in about a dozen cool stars, mainly with HST/STIS. The UV
coronal forbidden lines are important because they can be observed
with velocity resolution of better than 15 km/s, whereas even the
state-of-the-art X-ray spectrometers on Chandra can manage only 300
km/s in the kilovolt band where lines of highly ionized iron more
commonly are found. The kinematic properties of hot coronal plasmas,
which are of great interest to theorists and modelers, thus only are
accessible in the UV at present. The bad news is that the UV coronal
forbidden lines are faint, and were captured only in very deep
observations with STIS. The good news is that 3rd-generation Cosmic
Origins Spectrograph, slated for installation in HST by SM4, in a mere
25 minute exposure with its G130M mode can duplicate the sensitivity
of a landmark 25-orbit STIS E140M observation of AD Leo, easily the
deepest such exposure of a late-type star so far. Our goal is to build
up understanding of the properties of Fe XII and Fe XXI in additional
objects beyond the current limited sample: how the lineshapes depend
on activity, whether large scale velocity shifts can be detected, and
whether the dynamical content of the lines can be inverted to map the
spatial morphology of the stellar corona (as in "Doppler Imaging'').
In other words, we want to bring to bear in the coronal venue all the
powerful tricks of spectroscopic remote sensing, well in advance of
the time that this will be possible exploiting the corona's native
X-ray radiation. The 1290-1430 band captured by side A of G130M also
contains a wide range of key plasma diagnostics that form at
temperatures from below 10, 000 K (neutral lines of CNO), to above
200, 000 K (semi-permitted O V 1371), including the important bright
multiplets of C II at 1335 and Si IV at 1400; yielding a diagnostic
gold mine for the subcoronal atmosphere. Because of the broad value of
the SNAP spectra, beyond the coronal iron project, we waive the normal
proprietary rights.

COS/FUV 11686

The Cosmological Impact of AGN Outflows: Measuring Absolute Abundances
and Kinetic Luminosities

AGN outflows are increasingly invoked as a major contributor to the
formation and evolution of supermassive black holes, their host
galaxies, the surrounding IGM, and cluster cooling flows. Our HST/COS
proposal will determine reliable absolute chemical abundances in six
AGN outflows, which influences several of the processes mentioned
above. To date there is only one such determination, done by our team
on Mrk 279 using 16 HST/STIS orbits and 100 ksec of FUSE time. The
advent of COS and its high sensitivity allows us to choose among
fainter objects at redshifts high enough to preclude the need for
FUSE. This will allow us to determine the absolute abundances for six
AGN (all fainter than Mrk 279) using only 40 HST COS orbits. This will
put abundances studies in AGN on a firm footing, an elusive goal for
the past four decades. In addition, prior FUSE observations of four of
these targets indicate that it is probable that the COS observations
will detect troughs from excited levels of C III. These will allow us
to measure the distances of the outflows and thereby determine their
kinetic luminosity, a major goal in AGN feedback research.

We will use our state of the art column density extraction methods and
velocity-dependent photoionization models to determine the abundances
and kinetic luminosity. Previous AGN outflow projects suffered from
the constraints of deciding what science we could do using ONE of the
handful of bright targets that were observable. With COS we can choose
the best sample for our experiment. As an added bonus, most of the
spectral range of our targets has not been observed previously,
greatly increasing the discovery phase space.

WFC3/ACS/IR 11677

Is 47 Tuc Young? Measuring its White Dwarf Cooling Age and Completing
a Hubble Legacy

With this proposal we will firmly establish the age of 47 Tuc from its
cooling white dwarfs. 47 Tuc is the nearest and least reddened of the
metal-rich disk globular clusters. It is also the template used for
studying the giant branches of nearby resolved galaxies. In addition,
the age sensitive magnitude spread between the main sequence turnoff
and horizontal branch is identical for 47 Tuc, two bulge globular
clusters and the bulge field population. A precise relative age
constraint for 47 Tuc, compared to the halo clusters M4 and NGC 6397,
both of which we recently dated via white dwarf cooling, would
therefore constrain when the bulge formed relative to the old halo
globular clusters. Of particular interest is that with the higher
quality ACS data on NGC 6397, we are now capable with the technique of
white dwarf cooling of determining ages to an accuracy of +/-0.4 Gyrs
at the 95% confidence level. Ages derived from the cluster turnoff are
not currently capable of reaching this precision. The important role
that 47 Tuc plays in galaxy formation studies, and as the metal-rich
template for the globular clusters, makes the case for a white dwarf
cooling age for this metal-rich cluster compelling.

Several recent analyses have suggested that 47 Tuc is more than 2 Gyrs
younger than the Galactic halo. Others have suggested an age similar
to that of the most metal poor globular clusters. The current
situation is clearly uncertain and obviously a new approach to age
dating this important cluster is required.

With the observations of 47 Tuc, this project will complete a legacy
for HST. It will be the third globular cluster observed for white
dwarf cooling; the three covering almost the full metallicity range of
the cluster system. Unless JWST has its proposed bluer filters (700
and 900 nm) this science will not be possible perhaps for decades
until a large optical telescope is again in space. Ages for globular
clusters from the main sequence turnoff are less precise than those
from white dwarf cooling making the science with the current proposal
truly urgent.

ACS/WFC3 11670

The Host Environments of Type Ia Supernovae in the SDSS Survey

The Sloan Digital Sky Survey Supernova Survey has discovered nearly
500 type Ia supernovae and created a large, unique, and uniform sample
of these cosmological tools. As part of a comprehensive study of the
supernova hosts, we propose to obtain Hubble ACS images of a large
fraction of these galaxies. Integrated colors and spectra will be
measured from the ground, but we require high-resolution HST imaging
to provide accurate morphologies and color information at the site of
the explosion. This information is essential in determining the
systematic effects of population age on type Ia supernova luminosities
and improving their reliability in measuring dark energy. Recent
studies suggest two populations of type Ia supernovae: a class that
explodes promptly after star-formation and one that is delayed by
billions of years. Measuring the star-formation rate at the site of
the supernova from colors in the HST images may be the best way to
differentiate between these classes.

WFC3/UVIS 11657

The Population of Compact Planetary Nebulae in the Galactic Disk

We propose to secure narrow- and broad-band images of compact
planetary nebulae (PNe) in the Galactic Disk to study the missing link
of the early phases of post-AGB evolution. Ejected AGB envelopes
become PNe when the gas is ionized. PNe expand, and, when large
enough, can be studied in detail from the ground. In the interim, only
the HST capabilities can resolve their size, morphology, and central
stars. Our proposed observations will be the basis for a systematic
study of the onset of morphology. Dust properties of the proposed
targets will be available through approved Spitzer/IRS spectra, and so
will the abundances of the alpha- elements. We will be able thus to
explore the interconnection of morphology, dust grains, stellar
evolution, and populations. The target selection is suitable to
explore the nebular and stellar properties across the galactic disk,
and to set constraints on the galactic evolutionary models through the
analysis of metallicity and population gradients.

ACS/WFC 11655

Dynamics of the Galactic Bulge/bar

We request second-epoch ACS observations of four star fields in the
Galactic bar. These will allow us to measure proper motions for tens
of thousands of stars well below the turnoff, to construct a dynamical
model for the bulge/bar (in combination with data already in hand from
other HST fields, and from VLT spectroscopy), and hence to take a
unique look at the internal dynamical structure of the central regions
of our Galaxy. By relating the kinematics with stellar population we
can elucidate the formation history of the bulge and bar, and their
relation to the surrounding Galactic disk. This is a resubmission of
an approved Cycle 15 proposal that was hit by the ACS malfunction.

STIS/CC/MA 11609

NGC 6266: The Smoking Gun of Intermediate-Mass Black Holes in Galactic
Globular Clusters?

The existence of intermediate-mass black holes (IMBHs) in star
clusters has been predicted by a variety of theoretical arguments and,
more recently, by several large, realistic sets of collisional N-body
simulations. Establishing their presence or absence at the centers of
globular clusters would profoundly impact our understanding of
problems ranging from the formation and long-term dynamical evolution
of stellar systems, to the nature of the seeds and the growth
mechanisms of the supermassive black holes (BHs) that inhabit the
centers of most large, luminous galaxies. Observationally, the
unambiguous signature of a massive central BH would be the discovery
of central, unresolved X-ray or radio emission that is not consistent
with more common stellar-mass accreting objects or pulsars. Yet, due
to the largely uncertain details of accretion modeling, a precise mass
determination of a central BH must necessarily come from stellar
dynamics. This goal has not been achieved to date at the centers of
Galactic globular clusters because of lack of adequate data as well as
the use of too simplified methods of analysis. This situation can be
overcome today through the combination of HST proper-motion
measurements and state-of-the-art dynamical models specifically
designed to take full advantage of this type of dataset. In this
project, we will use two HST orbits to obtain another epoch of
observations of NGC 6266. This cluster has photometric and structural
properties that are consistent with current theoretical expectations
for a cluster harboring an IMBH. Even more importantly, it is the only
Galactic globular cluster for which there exists a detection of radio
emission coincident with the cluster's core, and with a flux density
that appears to rule out a stellar or binary origin. The goal of our
project is to obtain proper motion measurements to either confirm an
IMBH in this cluster and measure its mass, or to set limits to its
mass and existence.

ACS/WFC3 11593

Dynamical Masses of the Coolest Brown Dwarfs

T dwarfs are excellent laboratories to study the evolution and the
atmospheric physics of both brown dwarfs and extrasolar planets. To
date, only a single T dwarf binary has a dynamical mass determination,
and more are sorely needed. The prospects of measuring more dynamical
masses over the next decade are limited to 6 known short-period T
dwarf binaries. We propose here to obtain Long-Term HST/ACS monitoring
for the 3 of the 6 binaries which cannot be resolved with AO from the
ground. Upon completion, our program will substantially increase the
number of T dwarf dynamical mass measurements and thereby provide key
benchmarks for testing theoretical models of ultracool objects.

COS/FUV/STIS/CCD/MA1 11592

Testing the Origin(s) of the Highly Ionized High-Velocity Clouds: A
Survey of Galactic Halo Stars at z3 kpc

Cosmological simulation predicts that highly ionized gas plays an
important role in the formation and evolution of galaxies and their
interplay with the intergalactic medium. The NASA HST and FUSE
missions have revealed high-velocity CIV and OVI absorption along
extragalactic sightlines through the Galactic halo. These highly
ionized high-velocity clouds (HVCs) could cover 85% of the sky and
have a detection rate higher than the HI HVCs. Two competing, equally
exciting, theories may explain the origin of these highly ionized
HVCs: 1) the "Galactic" theory, where the HVCs are the result of
feedback processes and trace the disk-halo mass exchange, perhaps
including the accretion of matter condensing from an extended corona;
2) the "Local Group" theory, where they are part of the local warm-hot
intergalactic medium, representing some of the missing baryonic matter
of the Universe. Only direct distance determinations can discriminate
between these models. Our group has found that some of these highly
ionized HVCs have a Galactic origin, based on STIS observations of one
star at z5.3 kpc. We propose an HST FUV spectral survey to search for
and characterize the high velocity NV, CIV, and SiIV interstellar
absorption toward 24 stars at much larger distances than any previous
searches (4d21 kpc, 3|z|13 kpc). COS will provide atomic to highly
ionized species (e.g.,OI, CII, CIV, SiIV) that can be observed at
sufficient resolution (R~22, 000) to not only detect these highly
ionized HVCs but also to model their properties and understand their
physics and origins. This survey is only possible because of the high
sensitivity of COS in the FUV spectral range.

WFC3/IR 11591

Are Low-Luminosity Galaxies Responsible for Cosmic Reionization?

Our group has demonstrated that massive clusters, acting as powerful
cosmic lenses, can constrain the abundance and properties of
low-luminosity star-forming sources beyond z~6; such sources are
thought to be responsible for ending cosmic reionization. The large
magnification possible in the critical regions of well-constrained
clusters brings sources into view that lie at or beyond the limits of
conventional exposures such as the UDF. We have shown that the
combination of HST and Spitzer is particularly effective in delivering
the physical properties of these distant sources, constraining their
mass, age and past star formation history. Indirectly, we therefore
gain a valuable glimpse to yet earlier epochs. Recognizing the result
(and limitations) of blank field surveys, we propose a systematic
search through 10 lensing clusters with ACS/F814W and
WFC3/[F110W+F160W] (in conjunction with existing deep IRAC data). Our
goal is to measure with great accuracy the luminosity function at z~7
over a range of at least 3 magnitude, based on the identification of
about 50 lensed galaxies at 6.5z8. Our survey will mitigate cosmic
variance and extend the search both to lower luminosities and, by
virtue of the WFC3/IRAC combination, to higher redshift. Thanks to the
lensing amplification spectroscopic follow-up will be possible and
make our findings the most robust prior to the era of JWST and the
ELTs.

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/UVIS 11565

A Search for Astrometric Companions to Very Low-Mass, Population II
Stars

We propose to carry out a Snapshot search for astrometric companions
in a subsample of very low-mass, halo subdwarfs identified within 120
parsecs of the Sun. These ultra-cool M subdwarfs are local
representatives of the lowest-mass H burning objects from the Galactic
Population II. The expected 3-4 astrometric doubles that will be
discovered will be invaluable in that they will be the first systems
from which gravitational masses of metal-poor stars at the bottom of
the main sequence can be directly measured.

COS/NUV/FUV 11555

Transition Region and Chromospheric Activity on Low Metallicity
Arcturus Moving Group `Alien' Dwarfs

How does low metallicity affect the heating and resultant temperature
structure of the chromospheres, transition regions, and coronae of old
solar-like dwarf stars?

The Arcturus Moving Group is very likely a remnant of the merger of a
dwarf galaxy with the Milky Way Galaxy in the distant (~ 7- 8 Gyr)
past. This kinematically distinct group has members that are located
very close to the Sun, allowing study of stellar activity on very old,
low metallicity stars that typically would not be possible. We propose
to obtain COS G140L spectra of four dwarf star members of the Arcturus
Moving Group to measure the fluxes of their transition region and
upper chromospheric emission lines and to investigate the effects of
low metallicity on the outer atmospheric radiative losses and
temperature structure. Our targets have metallicities of ~ 20% solar
or less, spectral types F9 - M4, and are at distances less than 25 pc
from the Sun. COS is the only UV spectrograph that is capable of
registering the FUV spectra of these stars in a reasonable number of
HST orbits.

 




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