Status Report

NASA Hubble Space Telescope Daily Report #4045

By SpaceRef Editor
February 8, 2006
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NASA Hubble Space Telescope Daily Report #4045

HUBBLE SPACE TELESCOPE – Continuing to collect World Class Science


PERIOD COVERED: UT February 07, 2006 (DOY 038)


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/SBC 10507

High resolution imaging of Jupiter’s diffuse auroral emissions inside and outside the main oval during solar

The analysis of HST-STIS FUV images has greatly and quickly advanced our knowledge of the magnetospheric mechanisms producing the auroral emissions on the giant planets. However, these studies were limited to the brightest emissions and very little has been said about the fainter emissions, mainly because of the lower S/N. We propose to image the faint auroral emissions on Jupiter which could not be observed with STIS. We will take full advantage of ACS/SBC’s higher sensitivity to observe the diffuse auroral FUV emissions appearing poleward and directly equatorward of Jupiter’s main auroral oval in the northern hemisphere. This proposal has the potential to reveal new magnetosphere-ionosphere coupling mechanisms especially those involving solar wind interactions with a giant planet.

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.


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.


NICMOS Post-SAA calibration – CR Persistence Part 2

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.

WFPC2 10745


This calibration proposal is the Cycle 14 routine internal monitor for WFPC2, to be run weekly to monitor the health of the cameras. A variety of internal exposures are obtained in order to provide a monitor of the integrity of the CCD camera electronics in both bays {both gain 7 and gain 15 — to test stability of gains and bias levels}, a test for quantum efficiency in the CCDs, and a monitor for possible buildup of contaminants on the CCD windows. These also provide raw data for generating annual super-bias reference files for the calibration pipeline.


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


10120 – GSAcq(2,1,2) results in finelock backup (1,0,1) due to scan step limit exceeded on FGS-2 038/09:45:57z

The GSAcq(2,1,2) scheduled at 038/09:45:57 – 09:53:34 Z resulted in finelock backup (1,0,1) using FGS-1, due to scan step limit exceeded on FGS-2. Prior OBAD2 at 038/09:41:27 had total attitude correction (RSS) value of 6.65 arcseconds.

10121 – FGS1 enters CT twice @ 034/06:55z

OTA SE review of PTAS processing data revealed that FGS1 entered CT twice before achieving CT-DV during GSAcq(1,2,2) scheduled for 2006/034 06:52:54.


17597-2 – FHST Stuck-on-Bottom Macro Execution @ 038/22:44z


                         SCHEDULED      SUCCESSFUL
GSacq               10                     10
REacq               05                      05
OBAD with Maneuver  24                       24


FHST Stuck on Bottom Macro Execution

FHST 3 was observed to be Stuck on Bottom briefly during a 1st OBAD at ~ 038/22:20. Before the OBAD completed, FHST 3 released from its SOB condition and achieved Valid Rate on a pair of stars with catalog magnitudes of 5.8 and 6.87. This situation presented an opportunity to test the Stuck on Bottom macro, if FHST 3 could be commanded to leave the stars it was tracking and (perhaps) stick at the bottom again. Since all three FHSTs were available (FHST 1 was the rate controller), there was little risk to the forthcoming acquisition involved in breaking FHST 3 off of its stars. The SOB macro commanding for FHST 3 was sent at 038/22:43, and again at 038/22:44.

Reviewing telemetry from the commanding events, the FHST 3 star magnitude threshold is seen to change from 6th to 5th; however, the combined brightness of the stars that FHST 3 was tracking resulted in an apparent star magnitude between 4.97 and 5.06. Therefore FHST 3 did not leave the stars. Unfortunately this provides us no information concerning the effectiveness of the SOB macro in clearing SOB events.

SpaceRef staff editor.