Status Report

NASA Hubble Space Telescope Daily Report #4074

By SpaceRef Editor
March 21, 2006
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NASA Hubble Space Telescope Daily Report #4074

HUBBLE SPACE TELESCOPE – Continuing to collect World Class Science


PERIOD COVERED: UT March 20, 2006 (DOY 079)



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 10491

A Snapshot Survey of the most massive clusters of galaxies

We propose a snapshot survey of a sample of 124 high X-ray luminosity clusters in the redshift range 0.3-0.7. Similarly luminous clusters at these redshifts frequently exhibit strong gravitational lensing. The proposed observations will provide important constraints on the nature of the cluster mass distributions and a set of optically bright, lensed galaxies for further 8-10m spectroscopy. We acknowledge the broad community interest in this sample and waive our data rights for these observations.

ACS/WFC 10524

Blue Stragglers: a key stellar population to probe internal cluster dynamics

This proposal is part of a coordinated project devoted to understand the interplay of globular cluster {GC} dynamics and the formation and evolution of blue straggler stars {BSS}. By using a combination of HST and ground-based observations we are constructing complete BSS surveys in a sample of GCs; complete BSS surveys require mid-UV HST observations in the center and wide field CCD ground based observations under excellent seeing conditions of the exterior. Up to now only four clusters have been surveyed in this way and the results are surprising: in three GCs {M3, 47 Tuc, NGC 6752} we have discovered that the BSS radial distribution is bimodal, highly peaked in the cluster center, rapidly decreasing at intermediate radii and rising again at large radii {Ferraro et al. 1997, 2004, Sabbi et al. 2004}, conversely BSS population in Omega Centauri does not show any signature of the segregation which would be expected for a class of objects arising from either stellar interactions or binarity {Ferraro et al. 2005}. These observational facts are opening a new prospective in the study of the formation processes and evolution of BSS in GCs. By using extensive simulations, we demonstrated that the spatial distribution of BSS observed in 47 Tuc can be only reproduced if a sizable fraction of BSS is generated {via mass transfer in primordial binaries} in the peripheral region of the cluster {Mapelli et al 2004}, thus excluding a purely collisional formation scenario. Here we propose mid-UV imaging of a few clusters suspected of harboring a large population of central BSS and a few known to have many BSS the external region. These are good candidates for determining accurate BSS radial distributions. The modest amount of time proposed here will go far to determine the ubiquity of BSS bimodality and to constrain models of dynamical evolution. Since we believe the proposed observations would be useful to the entire stellar community {for multifold purposes} we waive the propretary period.

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.


The link between X-ray source and stellar populations in M81

We propose to perform a deep v~26-27.0 HST-ACS survey of the nearby {3.6 Mpc} spiral galaxy M~81 in order to study the nature of its X-ray source populations detected with Chandra. For the first time in a galaxy other than the Milky-Way or the Magelanic Clouds, we will classify X-ray sources as High-Mass and Low-Mass X-ray binaries {HMXBs, LMXBs} and investigate how these populations depend on their galactic environment. The classification will be performed {a} by finding and classifying unique optical counterparts for the X-ray sources and {b} studying the stellar populations in their vicinity. Both tasks require the <0.1'' resolution of HST-ACS which matches well the positional accuracy of Chandra. Finally we will use these results together with X-ray binary evolution synthesis models in order to constrain X-ray binary {XRB} evolution channels. These data will also be a great resource for studies of the star-formation and star- cluster populations in one of the prototypical spiral galaxies.

FGS 10757

Monitoring FGS1r’s Interferometric Response as a Function of Spectral Color

This proposal obtains reference point source Transfer Functions {S-Curves} for FGS1r through the F583W filter and the F5ND attenuator at the center position of the FGS1r FOV for a variety of stars of different spectral types. These Transfer Functions are needed to support the analysis of GO science data for the study of close and wide binary star systems and for determining the angular size and shape of extended sources. This proposal observes stars that have been observed in previous cycles to monitor the long term evolution of the FGS1r S-curves. This proposal also {1} monitors the FGS1r Lateral Color response {using stars Latcol-A and Latcol-B}, {2} calibrates the “Pos/Trans” bias of a star’s position as determined from Transfer mode and Position mode observations, and {3} calibrates the shift of a star’s centroid when observed with F5ND relative to that when observed with F583W.

NIC2 10527

Imaging Scattered Light from Debris Disks Discovered by the Spitzer Space Telescope Around 20 Sun-like Stars

We propose to use the high contrast capability of the NICMOS coronagraph to image a sample of newly discovered circumstellar disks associated with sun-like stars. These systems were identified by their strong thermal infrared emission with the Spitzer Space Telescope as part of the Spitzer Legacy Science program titled, “The Formation and Evolution of Planetary Systems {FEPS}.” Modelling of the thermal excess emission in the form of spectral energy distributions alone cannot distinguish between narrowly confined high opacity disks and broadly distributed, low opacity disks. However, our proposed NICMOS observations can, by imaging the light scattered from this material. Even non- detections will place severe constraints on the disk geometry, ruling out models with high optical depth. Unlike previous disk imaging programs, our program contains a well defined sample of solar mass stars covering a range of ages from ~10Myrs to a few Gyrs, allowing us to study the evolution of disks from primordial to debris for the first time. These results will greatly improve our understanding of debris disks around Sun- like stars at stellar ages nearly 10x older than any previous investigation. Thus we will have fit a crucial piece into the puzzle concerning the formation and evolution of our own solar system.

WFPC2 10749

Earth Flats

This proposal monitors flatfield stability. This proposal obtains sequences of Earth streak flats to construct high quality flat fields for the WFPC2 filter set. These flat fields will allow mapping of the OTA illumination pattern and will be used in conjuction with previous internal and external flats to generate new pipeline superflats. These Earth flats will complement the Earth flat data obtained during cycles 4-13.


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


10177 – GSAcq(1,3,1) results in finelock backup (3,0,3) due to scan step limit exceeded on FGS-1 @ 079/1737z

The GSAcq(1,3,1) scheduled at 079/17:37:17 – 17:44:54 resulted in finelock backup (3,0,3) using FGS-3, due to scan step limit exceeded on FGS-1. Pre-acquisition OBADs were successful. OBAD2 at 079/17:32:47 had total attitude correction (RSS) value of 15.02 arcseconds.



                           SCHEDULED      SUCCESSFUL
FGS GSacq                 11                    11
FGS REacq                 03                    03
OBAD with Maneuver    23                    23


SpaceRef staff editor.