Status Report

NASA Hubble Space Telescope Daily Status Report #4054

By SpaceRef Editor
February 21, 2006
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NASA Hubble Space Telescope Daily Status Report #4054

HUBBLE SPACE TELESCOPE – Continuing to collect World Class Science


PERIOD COVERED: UT February 20, 2006 (DOY 051)


ACS/HRC 10609

Sizes, Shapes, and SEDs: Searching for Mass Segregation in the Super Star Clusters of Nearby Starburst

We propose to investigate mass segregation and star cluster evolution and dissolution processes in Super Star Cluster {SSC} populations in a small sample of nearby starburst galaxies. ACS/HRC and NICMOS images of these nearby {d < 10 Mpc} starbursts can reveal evidence for mass segregation in the form of variations in size, shape, and color of the SSCs as a function of wavelength. The compactness of the cluster light profiles, and hence the stellar mass distributions, is a critical indicator of the likely fate of an SSC: long life and eventual evolution into a globular-like cluster, or dissolution. These observations will allow us to generate spectral energy distributions {SEDs} for a large sample of the SSCs at all ages and extinctions in each system. We will combine the SEDs with population synthesis models and existing ground- based spectra and Spitzer images to estimate ages, reddenings, and masses thus derive a more complete picture of the star-formation histories of the galaxies. For the brightest and most likely virialized among the SSCs we will also constrain their initial mass functions {IMFs} using high- resolution spectroscopy. Conclusions about IMFs from this technique require detailed information about the SSC concentration, light profiles, and virial status, which are only possible via ACS data. The proposed observations will provide an extensive and comprehensive data set for a large number of SSCs. By addressing the issues of mass segregation, evaporation, and destruction of SSC populations, the proposed observations will provide strong constraints on theories regarding the processes involved in the formation and evolution of SSCs and globular clusters. Given the dire predictions for the lifetime of HST, and its tremendous impact on the study of SSCs, we feel that the proposed observations not only are necessary and timely {even urgent} but will also be a fitting { and possibly final} addition to HST's legacy in the study of starburst SSCs.

ACS/HRC 10623

HST Optical Snapshot Survey of Intermediate Redshift Ultraluminous Infrared Galaxies

Ultraluminous infrared galaxies {ULIGs} are commonly believed to be a transitory phase in the evolution of disk galaxy mergers into QSOs. However, a recently reported discrepancy between the morphological and structural properties of z < 0.13 ULIGs and z = 0.12-0.25 QSOs with M{V} < -23.5 has cast doubt on their evolutionary connection. We propose an ACS snapshot survey of a sample of 39 ULIGs with z = 0.35-1.0. These galaxies are the best suited for comparison with luminous z=0.12-0.25 QSOs because {1} they are at larger lookback times than local ULIGs, and thus are likely representative of the systems that evolve into lower redshift luminous QSOs, {2} they have luminosities comparable to luminous QSOs and, {3} they are selected in a manner that biases the sample towards harboring imbedded AGN, and thus are the most likely precursors to optical QSOs. High resolution HST ACS images will allow a determination of galaxy morphology and reveal the presence of bright AGN. The 2-D profile of each galaxy will be modeled using GALFIT, with the AGN comprising one component of the fit where applicable to better characterize the underlying galaxy. Fundamental parameters {effective radius and surface brightness, and F814W-band magnitude} of the underlying galaxy will thus be measured and compared with the host galaxies of the luminous QSO sample. This imaging campaign will consume a modest amount of HST time, but will provide for the first time a statistically significant view of ULIGs at look-back times of 30-65% the age of the universe, and sufficient resolution and sensitivity to conduct a meaningful comparison with z=0.12-0.25 QSOs, as well as with local {z < 0.3} IRAS-detected and distant {z > 2} SCUBA-detected ULIGs.


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 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 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 10710

Hubble Heritage Observations of ESO 325-G004

The Hubble Heritage team will use a single pointing of ACS WFC to obtain F475W and F555W images as part of a public release image.

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.

FGS 10610

Astrometric Masses of Extrasolar Planets and Brown Dwarfs

We propose observations with HST/FGS to estimate the astrometric elements {perturbation orbit semi-major axis and inclination} of extra-solar planets orbiting six stars. These companions were originally detected by radial velocity techniques. We have demonstrated that FGS astrometry of even a short segment of reflex motion, when combined with extensive radial velocity information, can yield useful inclination information {McArthur et al. 2004}, allowing us to determine companion masses. Extrasolar planet masses assist in two ongoing research frontiers. First, they provide useful boundary conditions for models of planetary formation and evolution of planetary systems. Second, knowing that a star in fact has a plantary mass companion, increases the value of that system to future extrasolar planet observation missions such as SIM PlanetQuest, TPF, and GAIA.

NIC1 10517

Imaging Astrometrically-Discovered Brown Dwarfs

We propose to image the astrometrically discovered companions of three M-dwarfs with NICMOS to more tightly constrain their masses and determine their stellar or sub-stellar natures. Each of these systems has been observed with a sensitive ground-based adaptive optics system and no companions have been detected. NICMOS results will eliminate an ambiguity in the astrometric mass measurements that arises because a companion that contributes significantly to the visible light reduces the motion of the center of light and mimics a small motion of the center of mass. In addition the astrometric measurements made with NICMOS will fix the scale of the system, distinguishing among possible orbits. Finally the color photometry will constrain the spectral types to within a couple of subtypes. When we measure the masses of astrophysical objects, we test and assist the development of the theoretical mass models. Models are based upon parameters such as age and metallicity. Determining the correct mass thus deepens our understanding of the fundamental physics of stars and substellar objects

S/C/NIC1 10724

NICMOS Focus Monitoring

The purpose of this proposal is to determine the best focus for all three NICMOS detectors. The program will be executed every ~6 weeks. Each execution will concern a single detector, except two occasions which will include NIC3. In total NIC1 and NIC2 will be monitored 4 times each during the current cycle, while NIC3 will only be monitored twice. The program starts with a focus sweep using only the NIC1 camera {visit 11}. The following observation is with the NIC2 camera {visit 12} after about 45 days. This pattern is repeated throughout the period except for Jan 1-8 and Jul 1-8 where also the NIC3 camera is used. In total this will result in 10 orbits. Notice that VISIT #1 #2 refers to visits for #1 sequential visit number for a given camera #2 camera in question visit 32 is therefore the third visit for camera 2. Some tweaking of dates and sources are necessary to ensure visibility under 2-gyro mode. These are the dates and targets for Cycel14: Visit 11: Oct 01-08 NIC1 NGC1850 Visit 12: Nov 15-22 NIC2 NGC3603 Visit 21: Jan 01-15 NIC1 NGC3603 Visit 13: Jan 01-15 NIC3 NGC3603 Visit 22: Feb 15-22 NIC2 NGC3603 Visit 31: Apr 01-15 NIC1 NGC1850 Visit 32: May 22-31 NIC2 NGC3603 Visit 41: Jun 15-22 NIC1 NGC1850 Visit 23: Jun 15-22 NIC3 NGC1850 Visit 42: Aug 07-22 NIC2 NGC3603

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.

WFPC2 10779

WFPC2 WF4 Temperature Reduction Test #2

A serious 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. This is a second test to further reduce temperatures. Orbits: internal 26, external 1


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


10141 – REACQ(1,2,2) fails due to Search Radius Limit Exceeded on FGS 1@ 051/2222z

REACQ(1,2,2) at 051/22:18:05 failed due to Search Radius Limit Exceeded on FGS 1 at 22:22:46. Primary GSACQ(1,2,2) at 20:42:44 was successful. OBAD prior to REACQ at 22:12:49 computed an attitude correction of 13.52 arcseconds. OBAD after REACQ at 22:24:55 showed attitude error of -288.98 arcseconds on V2. Map computed by SAC at 22:25:40 showed -290.572 arcseconds error on V2. Six 486 ESB 1805 Moving Target Detected messages were recorded between 22:16:10 and 22:16:35. A05 was received at 22:22:46.


17646-0 – Patch WF2 UIDLE replacement htr set point in preparation for OOT#2 @ 051/2033z


                         SCHEDULED      SUCCESSFUL      FAILURE TIMES
FGS GSacq               09                     09
FGS REacq                06                    05                051/2222z 
(HSTAR 10141)
OBAD with Maneuver   30                    30


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