Status Report

NASA Hubble Space Telescope Daily Report #4047

By SpaceRef Editor
February 12, 2006
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NASA Hubble Space Telescope Daily Report #4047

HUBBLE SPACE TELESCOPE – Continuing to collect World Class Science


PERIOD COVERED: UT February 09, 2006 (DOY 040)


ACS/HRC 10557

Probing Asteroid Families for Evidence of Ultraviolet Space Weathering Effects

We propose six HST orbits to obtain UV reflectance spectra covering 200-460 nm of two Vesta asteroid family members, asteroid 832 Karin, and two Karin family members. These observations extend work done under a Cycle 13 AR grant, where we analyzed all of the existing IUE and HST S-class asteroids in the MAST database to investigate the effects of space weathering at UV wavelengths. Our hypothesis is that the manifestation of space weathering at UV wavelengths is a spectral bluing, in contrast with a spectral reddening at visible-NIR wavelengths, and that UV wavelengths can be more sensitive to relatively small amounts of weathering than longer wavelengths. The proposed observations will address two objectives: {1} Measure the UV-visible spectra of 832 Karin and two members of the young Karin family {absolute age of 5.8 My}, in order to determine whether intermediate space weathering is observable in objects likely pristine when they originated from the interior of Karin’s pa rent body. {2} Measure the UV-visible spectra of two members of the Vesta family to compare with our analysis of IUE Vesta spectra. These observations will probe Vesta’s interior, and test our hypothesis by contrasting the apparent amount of alteration on the surfaces of Vestoids with excavated material on Vesta.

ACS/HRC 10572

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

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/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 10587

Measuring the Mass Dependence of Early-Type Galaxy Structure

We propose two-color ACS-WFC Snapshot observations of a sample of 118 candidate early- type gravitational lens galaxies. Our lens-candidate sample is selected to yield {in combination with earlier results} an approximately uniform final distribution of 40 early-type strong lenses across a wide range of masses, with velocity dispersions {a dynamical proxy for mass} ranging from 125 to 300 km/s. The proposed program will deliver the first significant sample of low-mass gravitational lenses. All of our candidates have known lens and source redshifts from Sloan Digital Sky Survey data, and all are bright enough to permit detailed photometric and stellar- dynamical observation. We will constrain the luminous and dark-matter mass profiles of confirmed lenses using lensed-image geometry and lens-galaxy structural/photometric measurements from HST imaging in combination with dynamical measurements from spatially resolved ground-based follow-up spectroscopy. Hence we will determine, in unprecedented detail, the dependence of early-type galaxy mass structure and mass-to-light ratio upon galaxy mass. These results will allow us to directly test theoretical predictions for halo concentration and star-formation efficiency as a function of mass and for the existence of a cuspy inner dark- matter component, and will illuminate the structural explanation behind the fundamental plane of early-type galaxies. The lens-candidate selection and confirmation strategy that we propose has been proven successful for high-mass galaxies by our Cycle 13 Snapshot program {10174}. The program that we propose here will produce a complementary and unprecedented lens sample spanning a wide range of lens-galaxy masses.

ACS/WFC 10740

Absolute Photometric & Spectrophometric Calibration

This program has several goals: 1.}Verify repeatability of the ACS instrumentation on a single bright star to +/-0.2%. 2.}Determine any shift in the filter bandpasses since the preflight lab measurements. 3.}Determine the relative magnitude of the 3 primary WD calibrators to 0.1%. 4.}Refine the sensitivity calibration of the CCD prism and grisms at field center and determine the repeatability accuracy of this calibration. 5.}Determine the level of variability of the three HST red standard stars: VB-8 {M7}, 2M0038+18 {L3.5} and 2M0559-14 {T5}, and also measure their short wavelength {<7000A} fluxes. 6.}Cross calibrate with a faint STIS and NICMOS standard WD and solar analog star.


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 10103

FGS Astrometry of a Star Hosting an Extrasolar Planet: The Mass of Upsilon Andromedae d

We propose observations with HST/FGS to determine the astrometric elements {perturbation orbit semimajor axis and inclination} produced by the outermost extra-solar planet orbiting the F8V star Upsilon Andromedae. These observations will permit us to determine the actual mass of the planet by providing the presently unknown sin i factor intrinsic to the radial velocity method which discovered this object. An inclination, i = 30degrees, within the range of one very low precision determination using reanalyzed HIPPARCOS intermediate data products, would produce the observed radial velocity amplitude, K = 66 ms with a companion mass of ~8 M_Jupiter. Such a mass would induce in Upsilon Andromedae a perturbation semi-major axis, Alpha = 0arcs0012, easily within the reach of HST/FGS fringe tracking astrometry. The proposed observations will yield a planetary mass, rather than, as previous investigations have done, only suggest a planetary mass companion.

NIC1/NIC2/NIC3 8792

NICMOS Post-SAA calibration – CR Persistence Part 3

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.


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


10122 – GSAcq (1,3,1) failed due to Search Radius Limit Exceeded on FGS 1 @ 040/14:58z

GSAcq (1,3,1) scheduled @ 040/14:53:28 failed due to search radius limit exceeded on FGS 1. ESB a05 “Exceeded_SRL” received.

OBAD 1: V1 -457.32, V2 -2027.38, V3 229.63, RSS 2090.97

OBAD 2: V1 -3.10, V2 6.22, V3 -64.45, RSS 64.82


17642-2: FSW 2.9B EEPROM Installation @ 040/14:39z.


1446-1: Consolidated PCS/Safing Limit Modifications @ 040/1735z

                      SCHEDULED      SUCCESSFUL
FGS GSacq                08             07
FGS REacq                07             07
OBAD with Maneuver   22             22


FSW 2.9 Release B was successfully installed in HST486 EEPROM at 040/14:39:58z. The 2.9B EEPROM load was completed at 040/12:45:14z. The baseline EEPROM memory dump was completed at 040/13:59:51z and verified by FSW.

The Flight Operations Team (FOT) relocated this week from the STScI back to GSFC Missions Operations Room.

SpaceRef staff editor.