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Daily #4052



 
 
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Old February 17th 06, 02:46 PM posted to sci.astro.hubble
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Default Daily #4052

HUBBLE SPACE TELESCOPE - Continuing to collect World Class Science

DAILY REPORT #4052

PERIOD COVERED: UT February 47, 2006 (DOY 047)

OBSERVATIONS SCHEDULED

ACS/HRC 10556

Neutral Gas at Redshift z=0.5

Damped Lyman-alpha systems {DLAs} are used to track the bulk of the
neutral hydrogen gas in the Universe. Prior to HST UV spectroscopy,
they could only be studied from the ground at redshifts z1.65.
However, HST has now permitted us to discover 41 DLAs at z1.65 in our
previous surveys. Followup studies of these systems are providing a
wealth of information about the evolution of the neutral gas phase
component of the Universe. But one problem is that these 41
low-redshift systems are spread over a wide range of redshifts
spanning nearly 70% of the age of the Universe. Consequently, past
surveys for low-redshift DLAs have not been able to offer very good
precision in any small redshift regime. Here we propose an ACS-HRC-
PR200L spectroscopic survey in the redshift interval z=[0.37, 0.7]
which we estimate will permit us to discover another 41 DLAs. This
will not only allow us to double the number of low-redshift DLAs, but
it will also provide a relatively high-precision regime in the
low-redshift Universe that can be used to anchor evolutionary studies.
Fortunately DLAs have high absorption equivalent width, so
ACS-HRC-PR200L has high-enough resoultion to perform this proposed
MgII-selected DLA survey.

ACS/HRC 10738

Earth Flats

Sky flats will be obtained by observing the bright Earth with the HRC
and WFC. These observations will be used to verify the accuracy of the
flats currently in the pipeline and to monitor any changes. Weekly
coronagraphic monitoring is required to assess the changing position
of the spots.

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.

ACS/WFC 10577

Resolving the non-radiative shock in SN1006

An ACS image of the H alpha filament in the supernova remnant SN1006
will resolve the thickness of the H alpha emission zone. This will
permit us to derive an accurate pre-shock density, which in turn can
be used to model the time-dependent X-ray spectrum of the bright X-
ray ridge with no free parameters, thus benchmarking these widely used
models. We will also search for evidence of a shock precursor, and we
will use the scale of ripples in the shock to estimate the level of
density inhomogeneity in the pre-shock gas.

ACS/WFC/NIC3/WFPC2 10530

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.

NIC1/NIC2/NIC3 8793

NICMOS Post-SAA calibration - CR Persistence Part 4

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.

NIC2 10603

Multiwavelength Imaging of Edge-on Protoplanetary Disks: Quantifying
the Growth of Circumstellar Dust

Young, edge-on circumstellar disks are uniquely valuable laboratories
for the study of planet formation. In these objects, the central star
is occulted from direct view, significant PSF artifacts are absent,
and the disk is clearly seen as a central dust lane flanked by faint
disk reflected light. The detailed morphology of these nebulae and its
variation with wavelength provide crucial information on the disk
internal structure and the properties of its constituent dust grains.
A key observable is the slope defining the wavelength dependence of
the dust scattering opacity, which becomes shallower when grain growth
has taken place; multiwavelength resolved disk images are the key
dataset enabling such measurements. Recent analyses of three different
edge-on disks have revealed a diversity in their dust properties that
is indicative of different degrees of dust grain evolution having
taken place in each system. This characterization of disk grain
growth, when applied comparatively to a larger sample of these
objects, would enable the construction of an evolutionary sequence of
young disks at successive stages on the road to planet formation. In
pursuit of this goal, we have identified a sample of 15 edge-on disks
previously discovered by HST or groundbased telescopes, but for which
high fidelity, high spatial resolution images do not yet exist in both
the optical and near-infrared. We propose broad-band multicolor
imaging with NICMOS of all these targets, and ACS imaging of nine of
these targets In combination with existing data, the proposed images
will form a complete database of high resolution optical/near-IR
images for these 15 disk systems. Scattered light modeling will be
used to derive the disk structure and dust properties, yielding
results that will be of fundamental importance for our understanding
of grain properties during protoplanetary disk evolution.

FLIGHT OPERATIONS SUMMARY:

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

HSTARS:

10136 - GSAcq(1,2,2) failed due to search radius limit exceeded on FGS
1 @ 048/0818z

GSAcq(1,2,2) scheduled at 048/08:18:04 failed due to search radius
limit exceeded on FGS 1. Received ESB 1805 "T2G Moving Target
Detected" @ 048/08:12:49. Received ESB a05 "Exceeded SRL" @
048/08:23:25. OBAD #1: V1 454.41, V2 -413.52, V3 -185.24, RSS 641.72
OBAD #2: V1 18.16, V2 1.55, V3 18.31, RSS 25.83

COMPLETED OPS REQUEST: (None)

COMPLETED OPS NOTES: (None)

SCHEDULED SUCCESSFUL FAILURE TIMES
FGS
GSacq 08 07 048/0818z
(HSTAR 10136)
FGS REacq 06 06
OBAD with Maneuver 28 28

SIGNIFICANT EVENTS: (None)

 




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