Status Report

NASA Hubble Space Telescope Daily Report #4024

By SpaceRef Editor
January 10, 2006
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NASA Hubble Space Telescope Daily Report #4024

HUBBLE SPACE TELESCOPE – Continuing to collect World Class Science


PERIOD COVERED: UT January 09, 2006 (DOY 009)


ACS/HRC 10130

Systemic Proper Motions of the Magellanic Clouds from Astrometry with ACS: II. Second Epoch Images

We request second epoch observations with ACS of Magellanic Cloud fields centered on the 40 quasars in the LMC and SMC for which we have first epoch Cycle 11 data. The new data will determine the systemic proper motion of the Clouds. An extensive astrometric analysis of the first epoch data shows that follow-up observations with a two year baseline will allow us to measure the proper motion of the clouds to within 0.022 mas/year in each of the two orthogonal directions {assuming that we can image 25 quasars, i.e., with a realistic Snapshot Program completion rate}. The best weighted combination of all previous measurements has a seven times larger error than what we expect. We will determine the proper motion of the clouds with 2% accuracy. When combined with HI data for the Magellanic Stream this will constrain both the mass distribution in the Galactic Halo and theoretical models for the origin of the Magellanic Stream. Previous measurements are too crude for such constraints. Our data will provide by far the most accurate proper motion measurement for any Milky Way satellite.

ACS/HRC 10738

Earth Flats

Sky flats will be obtained by observing the bright Earth with the HRC and WFC. These observations will be used to verify the accuracy of the flats currently in the pipeline and to monitor any changes. Weekly coronagraphic monitoring is required to assess the changing position of the spots.


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 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 10615

Timing Studies of the X-ray Binary Populations in Globular Clusters

Close binaries are fundamental to the dynamical stability and evolution of globular clusters, but large populations have been extremely difficult to identify. Chandra X-ray images provide a revolutionary resource, revealing a few to dozens of low-luminosity X-ray sources in every cluster deeply examined; our own Chandra programs uniformly study these ubiquitous X-ray sources {close binaries and their progeny} in a dozen clusters. We have obtained multicolor, single-epoch, ACS images, from which to obtain initial optical counterparts, especially CVs {the dominant population in most clusters}, BY Dra’s, and qLMXBs. As HST capability for follow-on, confirming, spectra of our multicolor-selected counterparts is now severely curtailed, we propose an ACS time-series imaging program that will yield equivalent follow-on information for 5 of our clusters. The proposed ACS time-series data with 6 min resolution and 8 hr time-span, will: provide variability information to secure our suggested multicolor identifications; allow secure classifications of the various X-ray subpopulations {e.g., CVs vs. BY Dra’s}; yield quality lightcurves, whose shape will help test the notion that magnetic CVs are more common in globular clusters than the field; and, provide interesting contraints on the period distributions of cluster X-ray binaries.

NIC1/NIC2/NIC3 8793

NICMOS Post-SAA calibration – CR Persistence Part 4

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.

NIC3 10538

Near-IR Spectrophotometry of 2MASSWJ 1207334-393254B – An Extra-Solar Planetary Mass Companion

We propose to obtain “short” wavelength near-IR diagnostic and characterizing spectra of the very high probability candidate extra-solar giant planet {EGP} companion to 2MASSWJ 1207334- 393254 {2M1207}, a young brown dwarf and TW Hydrae Association member. Recent NICMOS camera 1 multi-band photometric imaging of the companion candidate, 0.77″ {54 AU projected} from 2M1207 – initially detected at longer wavelengths with VLT/NACO – implicate an object of several Jupiter masses based on cooling models of EGPs and the likely age of 2M1207 {~ 8 Myr}. Physical companionship of the EGP candidate with 2M1207 has been established at the 99.1% level of confidence via second-epoch NICMOS astrometric observations. Diagnostic spectra in the 0.8 to 1.9 micron region {unobtainable from the ground and overlapping the NICMOS imaging observations} will {a} critically inform on the physical nature of the EGP, {b} provide currently non-existing information to test/constrain theoretical models of EGP properties and evolution, and {c} unequivocally confirm the imaging of a bone fide EGP. Background light from 2M1207 would normally swamp the EGP spectrum with direct spectral imaging. To obviate this, we propose PSF-subtracted grism spectra of the EGP using 2M1207 as its own spectral template via two- orientation high-contrast image subtraction. The temporal stability of the HST+NICMOS PSF enables self-subtractions of targets at different field orientations resulting in contrast enhancements of 5 to 6 stellar magnitudes in the circumstellar background at ~ 0.8″ at these wavelengths. With the grism field oriented to place the EGP “above” and “below” 2M1207 {at two observational epochs} two independent spectra of the EGP will emerge from a difference image. This prototypical spectrum will serve to test and improve upon current models of young EGPs which predict flux suppression by molecular absorption in their atmospheres.

NIC3/ACS/WFC 10404

The Nature of Protocluster Galaxies at z=2.16: Morphology-Density and Color-Magnitude Relations

To establish the epoch when galaxy environment manifests itself as a large-scale evolutionary process, we propose to extend the study of galaxy colors and morphologies to a protocluster at z=2.16. Here the universe is only 3 Gyrs old and significant differences are expected between scenarios favoring a morphology-radius relation over a morphology-density relation. In addition, because the fractional age differences among cluster galaxies are larger, study of the color- magnitude relation provides considerable leverage for determining the epoch of early-type galaxy formation. To facilitate direct comparison to studies at lower redshift, one must probe the same rest-frame wavelengths with high photometric accuracy and at similar physical scales. Its near-infrared photometric stability {low, constant background} and ability to image large areas of sky at high angular-resolution {compared to adaptive optics} makes HST/NICMOS ideal for this program. Six pointings of NICMOS camera 3 will result in rest-frame optical, high resolution images of 16 confirmed protocluster members, and an additional 60 candidate protocluster members including 29 EROs. These galaxies were selected with a variety of techniques and span a range of projected radii within the protocluster. The proposed observations constitute a unique opportunity to extend the study of galaxies in overdense regions to an early time in cosmic history.

WFPC2 10777

WFPC2 WF4 Bay 1 Temperature Reduction Test #1

A 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 proposal tests methods to fix the problem by adjusting some temperatures inside WFPC2. 1 external and 24 internal orbits.


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

HSTARS: (None)

COMPLETED OPS REQUEST: 17618-0 – Patch WFPC2 UIDLE Replacement Heater Set Point (ARB OOT @ 009/12:27z


                         SCHEDULED      SUCCESSFUL
FGS GSacq               06                    06
FGS REacq               09                    09
OBAD with Maneuver  22                    22


Ops request 17618-0 to patch WF-2 UIDLE replacement heater upper set point to 12.2 degC was successfully completed at 009/12:28 the replacement heater will be monitored to ensure that it cycles on and off as expected.

SpaceRef staff editor.