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Daily #4081



 
 
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Old March 30th 06, 02:48 PM posted to sci.astro.hubble
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Default Daily #4081

HUBBLE SPACE TELESCOPE - Continuing to collect World Class Science

DAILY REPORT #4081

PERIOD COVERED: UT March 29, 2006 (DOY 089)

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/WFC 10729

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 10592

An ACS Survey of a Complete Sample of Luminous Infrared Galaxies in
the Local Universe

At luminosities above 10^11.4 L_sun, the space density of far-infrared
selected galaxies exceeds that of optically selected galaxies. These
`luminous infrared galaxies' {LIRGs} are primarily interacting or
merging disk galaxies undergoing enhanced star formation and Active
Galactic Nuclei {AGN} activity, possibly triggered as the objects
transform into massive S0 and elliptical merger remnants. We propose
ACS/WFC imaging of a complete sample of 88 L_IR 10^11.4 L_sun
luminous infrared galaxies in the IRAS Revised Bright Galaxy Sample
{RBGS: i.e., 60 micron flux density 5.24 Jy}. This sample is ideal
not only in its completeness and sample size, but also in the
proximity and brightness of the galaxies. The superb sensitivity,
resolution, and field of view of ACS/WFC on HST enables a unique
opportunity to study the detailed structure of galaxies that sample
all stages of the merger process. Imaging will be done with the F439W
and F814W filters {B and I-band} to examine as a function of both
luminosity and merger state {i} the evidence at optical wavelengths of
star formation and AGN activity and the manner in which instabilities
{bars and bridges} in the galaxies may funnel material to these active
regions, {ii} the relationship between star formation and AGN
activity, and {iii} the structural properties {AGN, bulge, and disk
components} and fundamental parameters {effective radius and surface
brightness} of LIRGs and their similarity with putative evolutionary
byproducts {elliptical, S0 and classical AGN host galaxies}. This HST
survey will also bridge the wavelength gap between a Spitzer imaging
survey {covering seven bands in the 3.6-160 micron range} and a GALEX
UV imaging survey of these galaxies, but will resolve complexes of
star clusters and multiple nuclei at resolutions well beyond the
capabilities of either Spitzer or GALEX. The combined datasets will
result in the most comprehensive multiwavelength study of interacting
and merging galaxies to date.

ACS/WFC 10605

Quantifying Star Formation and Feedback: The M81 Group Dwarf Galaxies

Studies of the impact of star formation via stellar winds and
supernovae {'feedback'} on the properties of a galaxy are of
fundamental importance to understanding galaxy evolution. One crucial
aspect in these studies is a precise census of the recent star
formation in a galaxy. The aim of this proposal is to obtain spatially
resolved star formation histories with a time resolution of roughly 30
Myr over the last 500 Myr in a carefully designed sample using the
absolutely unique capabilities of the ACS. Our sample comprises 10
galaxies in the M81 group which is host to a wide diversity of dwarf
star forming galaxies. They span ranges of 6 magnitudes in luminosity,
1000 in current star formation rate, and 0.5 dex in metallicity. The
ACS observations will allow us to directly observe the strength and
spatial relationships of all of the star formation in these galaxies
in the last 500 Myr. We can then quantify the star formation and
measure {1} the fraction of star formation that is triggered by
feedback, {2} the fraction of star formation that occurs in clusters
and associations, and {3} to what degree future star formation is
governed by the feedback from previous star formation. The ACS
observations will be complemented with high-quality ancillary data
collected by our team for all galaxies {e.g., Spitzer, UV/optical/NIR,
VLA HI}. We will calculate the energy created by star formation events
and compare it to the estimated energy deposited into the local ISM.
This will enable us to construct prescriptions of how star formation
and feedback depend on metallicity, size, gas content, and current
star formation rates in galaxies. Our resolved star formation maps
will be compared with star formation rates inferred from H-alpha, UV,
and IR observations - allowing an independent calibration of these
techniques. Recent ACS imaging by us of one galaxy in the same group
clearly demonstrates the feasibility of the proposed program. Most of
the sample galaxies are located in the CVZ, making this an extremely
efficient program.

ACS/WFC 10775

An ACS Survey of Galactic Globular Clusters

We propose to conduct an ACS/WFC imaging survey of Galactic globular
clusters. We will construct the most extensive and deepest set of
photometry and astrometry to-date for these systems reaching a main
sequence mass of ~0.2 solar mass with S/N = 10. We will combine these
data with archival WFPC2 and STIS images to determine proper motions
for the stars in our fields. The resultant cleaned cluster CMDs will
allow us to study a variety of scientific questions. These include
[but are not limited to] 1} the determination of cluster ages and
distances 2} the construction of main sequence mass functions and the
issue of mass segregation 3} the internal motions and dynamical
evolution of globular clusters, and 4} absolute cluster motions,
orbits, and the Milky Way gravitational potential. We anticipate that
the unique resource provided by the proposed treasury archive will
play a central role in the field of globular cluster studies for
decades, with a stature comparable to that of the Hubble Deep Field
for high redshift studies.

ACS/WFC/HRC 10536

What Are Stalled Preplanetary Nebulae? An ACS SNAPshot Survey

Essentially all planetary nebulae {PNs} are aspherical, whereas the
mass-loss envelopes of AGB stars are strikingly spherical. Our
previous SNAPshot surveys of a morphologically unbiased sample of
pre-planetary nebulae {PPNs} -- objects in transition between the AGB
and PN evolutionary phases -- show that roughly half our observed
targets are resolved, with bipolar or multipolar morphologies.
Spectroscopic observations of our sample confirm that these objects
have not yet evolved into planetary nebulae. Thus, the transformation
from spherical to aspherical geometries has already fully developed by
the time these dying stars have become PPNs. Although our current
studies have yielded exciting results, they are limited in two
important ways -- {1} the number of well-resolved objects is still
small {18}, and the variety of morphologies observed relatively
multitudinous, hence no clear trends can yet be established between
morphology and other source properties {e.g., near-IR, far-IR colors,
stellar spectral type, envelope mass}, and {2} the current samples are
strongly biased towards small PPNs, as inferred from their low
60-to-25 micron flux ratios [R{60/25}1]. However, the prototype of
objects with R{60/25}1, the Frosty Leo Nebula, has a puzzlingly large
post-AGB age {almost 10^4 yr} and a fairly cool central star, very
different from the expectations of single-star stellar evolutionary
models. A proposed, but still speculative, hypothesis for such objects
is that the slow evolution of the central star is due to backflow of
material onto the mass-losing star, retarding its evolution towards
the PN phase. This hypothesis has significant consequences for both
stellar and nebular evolution. We therefore propose a survey of PPNs
with R{60/25}1 which is heavily weighted towards the discovery of
such "stalled PPNs". Supporting kinematic observations using long-slit
optical spectroscopy {with the Keck}, millimeter and radio
interferometric observations {with OVRO, VLA & VLBA} are being
undertaken. The results from this survey {together with our previous
work} will allow us to draw general conclusions about the complex
mass-outflow processes affecting late stellar evolution, and will
provide crucial input for theories of post-AGB stellar evolution. Our
survey will produce an archival legacy of long-standing value for
future studies of dying stars.

ACS/WFC/WFC 10776

HST/ACS Mosaic of M82

A six-pointing ACS WFC mosaic of the galaxy M82 will be obtained in
four filters, B, V, I and H- alpha. Four orbits per pointing will
allow high-quality S/N images of the entire galaxy.

FLIGHT OPERATIONS SUMMARY:

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

HSTARS:

10187 - GSAcq (1,2,1) resulted in fine lock backup due to scan step
limit exceeded on FGS-1 088/20:08:44z

The GSAcq(1,2,1) scheduled at 088/20:04:59-20:12:06 resulted in
finelock backup (2,0,2) using FGS-2, due to scan step limit exceeded
on FGS-1. Pre-acquisition OBADs were successful. OBAD2 at 088/19:59:59
had total attitude correction (RSS) value of 13.41 arcseconds. OBAD
MAP had total attitude correction (RSS) value of 7.06 arcseconds

COMPLETED OPS REQUEST:
17676-0 - Eclipse Management, GMT Day 88 @ 088/10:21:43z
17675-2 - Patch SOC1 and SOC2 Safing Limits for Solar Eclipse 2006/088 @
088/10:33:51z
17677-0 - AGO GSTDN Engineering Test Supports @ 089/01:25z


COMPLETED OPS NOTES: (None)

SCHEDULED SUCCESSFUL
FGS GSacq 07 07
FGS REacq 08 08
OBAD with Maneuver 26 26

SIGNIFICANT EVENTS:

Eclipse Flash Report - 3/29/06

Two eclipse events occurred over the period of GMT 88/09:13 through
88/10:02. With the second eclipse occurring near middle of orbit day
and having a peak darkness of ~92 percent darkness, ROP PS-02 was
performed to minimize the impacts of this eclipse on the spacecraft.
The steps to increase the CSS failure timer was completed prior to the
first eclipse event at GMT 88/06:10. Additional steps were taken to
lower the SOC 1 and SOC 2 safemode limits by 10 A-hrs to 171 A-hr and
111 A-hr, respectively. This recommendation was performed as a
proactive measure. Resetting of these limits was completed by
88/10:32. ROP PS-02 was also completed by this time. Preliminary
results from the second eclipse event showed that at the start of that
orbit day the pressure-based SOC was 204 A-hr. After the eclipse,
Benchmark Reset Threshold was achieved about 12 minutes prior to EON.
The SOC reached 248 A-hr at EON (088/10:30).

 




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