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Daily #4044

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Old February 7th 06, 02:26 PM posted to sci.astro.hubble
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Default Daily #4044

HUBBLE SPACE TELESCOPE - Continuing to collect World Class Science


PERIOD COVERED: UT February 06, 2006 (DOY 037)


ACS/HRC 10525

Characterizing the Near-UV Environment of M Dwarfs: Implications for
Extrasolar Planetary Searches and Astrobiology

We propose SNAP observations with the ACS HRC PR200L prism, designed
to measure the near ultraviolet emission in a sample of 107 nearby M
dwarfs. The sample spans the mass range from 0.1 - 0.6 solar masses
{temperature range 2200K - 4000K} where the UV energy distributions
vary widely between active and inactive stars. The strength and
distribution of this UV emission can have critical consequences for
the atmospheres of attendant planets. Our proposed observations will
provide desperately needed constraints on models of the habitability
zone and the atmospheres of possible terrestrial planets orbiting M
dwarf hosts, and will be used to sharpen TPF target selection. In
addition, the NUV data will be used in conjunction with existing
optical, FUV and X-ray data to constrain a new generation of M dwarf
atmospheric models, and to explore unanswered questions regarding the
dynamo generation and magnetic heating in these low-mass stars.

ACS/HRC 10572

Resolving M32's Main Sequence: A Critical Test for Stellar Population

We propose to observe the M32 main-sequence turnoff {MSTO} with deep
ACS/HRC B and V images. Only the superior resolution and blue
sensitivity of ACS/HRC make this possible. M32 is the only elliptical
galaxy close enough to allow direct observation of its MSTO - it is a
vital laboratory for deciphering the stellar populations of all other
elliptical galaxies, which can only be studied by the spectra of their
integrated light, given their greater distances. Major questions about
M32's star formation history remain unanswered. Spectral studies
suggest that M32 underwent a recent burst of star formation 3 to 8
billion years ago; observation of the M32 MSTO will confirm this
directly. In the process, ACS will easily resolve more luminous
components: hot blue stars, luminous, intermediate-age red clump and
AGB stars, and any extended blue horizontal branch. These detailed
CMDs will provide a direct comparison with population synthesis models
for M32, providing a bridge to studies of the integrated light of more
distant elliptical galaxies, a crucial ingredient for understanding
their star formation histories. As M32 is projected against the edge
of the M31 disk, an essential part of our proposal includes deep
observation of an M31 disk field to allow the M32 photometry to be
background corrected. These observations will reveal the star
formation history of M31's outer disk and are thus of interest in
their own right.


ACS CCDs daily monitor

This program consists of a set of basic tests to monitor, the read
noise, the development of hot pixels and test for any source of noise
in ACS CCD detectors. The files, biases and dark will be used to
create reference files for science calibration. This programme will be
for the entire lifetime of ACS. Changes from cycle 13:- The default
gain for WFC is 2 e-/DN. As before bias frames will be collected for
both gain 1 and gain 2. Dark frames are acquired using the default
gain {2}. This program cover the period Oct, 2 2005- May, 29-2006. The
second half of the program has a different proposal number: 10758.

ACS/WFC 10522

Calibrating Star Formation: The Link between Feedback and Galaxy

Stellar feedback - the return of mass and energy from star formation
to the interstellar medium - is one of the primary engines of galaxy
evolution. Yet, the theoretical foundation of mechanical feedback is,
to date, unconstrained by observations. We propose to investigate this
fundamental aspect of star formation on a sample of two local actively
star-forming galaxies, NGC4449, and Holmberg II. The two galaxies have
been selected to occupy an unexplored, yet crucial for quantifying
mechanical feedback, niche in the two-parameter space of star
formation intensity and galaxy mass. ACS/WFC and WFPC2 narrow-band
observations in the light of H-beta, [OIII], H-alpha, and [NII] will
be obtained for both galaxies, in order to: {1} discriminate the
feedback- induced shock fronts from the photoionization regions; {2}
map the shocks inside and around the starburst regions; and {3}
measure the energy budget of the star-formation-produced shocks. These
observations, complemented by existing data, will yield: {1} the
efficiency of the feedback, i.e. the fraction of the star formation's
mechanical energy that is transported out of the starburst volume
rather than confined or radiated away; {2} the dependence of this
efficiency on the two fundamental parameters of star formation
intensity and stellar mass. The high angular resolution of HST is
crucial for separating the spatially narrow shock fronts {~5 pc,
~0.25" at 4 Mpc} from the more extended photoionization fronts. The
legacy from this project will be the most complete quantitative
measurement of the energetics associated with feedback processes. We
will secure the first milestone for placing feedback mechanisms on a
solid physical ground, and for understanding quantitatively their role
on the energetics, structure, and star formation history of galaxies
at all redshifts.

ACS/WFC 10543

Microlensing in M87 and the Virgo Cluster

Resolving the nature of dark matter is an urgent problem. The results
of the MACHO survey of the Milky Way dark halo toward the LMC indicate
that a significant fraction of the halo consists of stellar mass
objects. The VATT/Columbia survey of M31 finds a similar lens fraction
in the M31 dark halo. We propose a series of observations with ACS
that will provide the most thorough search for microlensing toward
M87, the central elliptical galaxy of the Virgo cluster. This program
is optimized for lenses in the mass range from 0.01 to 1.0 solar
masses. By comparing with archival data, we can detect lenses as
massive as 100 solar masses, such as the remnants of the first stars.
These observations will have at least 15 times more sensitivity to
microlensing than any previous survey, e.g. using WFPC2. This is due
to the factor of 2 larger area, factor of more than 4 more sensitivity
in the I-band, superior pixel scale and longer baseline of
observations. Based on the halo microlensing results in the Milky Way
and M31, we might expect that galaxy collisions and stripping would
populate the overall cluster halo with a large number of stellar mass
objects. This program would determine definitively if such objects
compose the cluster dark matter at the level seen in the Milky Way. A
negative result would indicate that such objects do not populate the
intracluster medium, and may indicate that galaxy harassment is not as
vigorous as expected. We can measure the level of events due to the
M87 halo: this would be the best exploration to date of such a lens
population in an elliptical galaxy. Star-star lensing should also be
detectable. About 20 erupting classical novae will be seen, allowing
to determine the definitive nova rate for this giant elliptical
galaxy. We will determine if our recent HST detection of an M87
globular cluster nova was a fluke, or indicative of a 100x higher rate
of incidence of cataclysmic variables and nova eruptions in globulars
than previously believed. We will examine the populations of variable
stars, and will be able to cleanly separate them from microlensing.


Probing Evolution And Reionization Spectroscopically {PEARS}

While imaging with HST has gone deep enough to probe the highest
redshifts, e.g. the GOODS survey and the Ultra Deep Field,
spectroscopic identifications have not kept up. We propose an ACS
grism survey to get slitless spectra of all sources in a wide survey
region {8 ACS fields} up to z =27.0 magnitude, and an ultradeep field
in the HUDF reaching sources up to z =28 magnitude. The PEARS survey
will: {1} Find and spectrocopically confirm all galaxies between
z=4-7. {2} Probe the reionization epoch by robustly determining the
luminosity function of galaxies and low luminosity AGNs at z = 4 - 6.
With known redshifts, we can get a local measure of star formation and
ionization rate in case reionization is inhomogeneous. {3} Study
galaxy formation and evolution by finding galaxies in a contiguous
redshift range between 4 z 7, and black hole evolution through a
census of low-luminosity AGNs. {4} Get a robust census of galaxies
with old stellar populations at 1 z 2.5, invaluable for checking
consistency with heirarchical models of galaxy formation. Fitting
these galaxies' spectra will yield age and metallicity estimates. {5}
Study star-formation and galaxy assembly at its peak at 1 z 2 by
identifying emission lines in star-forming galaxies, old populations
showing the 4000A break, and any combination of the two. {6} Constrain
faint white dwarfs in the Galactic halo and thus measure their
contribution to the dark matter halo. {7} Derive spectro-photometric
redshifts by using the grism spectra along with broadband data. This
will be the deepest unbiased spectroscopy yet, and will enhance the
value of the multiwavelength data in UDF and the GOODS fields to the
astronomical community. To this end we will deliver reduced spectra to
the HST archives.

FGS 10432

Precise Distances to Nearby Planetary Nebulae

We propose to carry out astrometry with the FGS to obtain accurate and
precise distances to four nearby planetary nebulae. In 1992, Cahn et
al. noted that ``The distances to Galactic planetary nebulae remain a
serious, if not THE most serious, problem in the field, despite
decades of study.'' Twelve years later, the same statement still
applies. Because the distances to planetary nebulae are so uncertain,
our understanding of their masses, luminosities, scale height, birth
rate, and evolutionary state is severely limited. To help remedy this
problem, HST astrometry can guarantee parallaxes with half the error
of any other available approach. These data, when combined with
parallax measurements from the USNO, will improve distance
measurements by more than a factor of two, producing more accurate
distances with uncertainties that are of the order of ~6%. Lastly,
most planetary nebula distance scales in the literature are
statistical. They require several anchor points of known distance in
order to calibrate their zero point. Our program will provide "gold
standard" anchor points by the end of 2006, a decade before any
anticipated results from future space astrometry missions.


NICMOS Post-SAA calibration - CR Persistence Part 2

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 images. Each observation will need its
own CRMAP, as different SAA passages leave different imprints on the
NICMOS detectors.

WFPC2 10748

WFPC2 CYCLE 14 Standard Darks

This dark calibration program obtains dark frames every week in order
to provide data for the ongoing calibration of the CCD dark current
rate, and to monitor and characterize the evolution of hot pixels.
Over an extended period these data will also provide a monitor of
radiation damage to the CCDs.

WFPC2 10778

WFPC2 WF4 Supplemental Darks

An anomaly has been found in images from the WF4 CCD in WFPC2. The WF4
CCD bias level appears to have become unstable, resulting in sporadic
images with either low or zero bias level. The severity and frequency
of the problem is rapidly increasing, and it is possible that WF4 will
soon become unusable if no work-around is found. The other three CCDs
{PC1, WF2, and WF3} appear to be unaffected and continue to operate
properly. These darks are to supplement those in program 10748 to
ensure sufficient dark frames for routine calibration. As the WF4
anomaly grows worse, we are beginning to see episodes where too many
darks are corrupted and are unusable.


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

HSTARS: (None)



FGS GSacq 08 08
FGS REacq 08 08
OBAD with Maneuver 19 19



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