Status Report

NASA Hubble Space Telescope Daily Status Report #4055

By SpaceRef Editor
February 23, 2006
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NASA Hubble Space Telescope Daily Status Report #4055

HUBBLE SPACE TELESCOPE – Continuing to collect World Class Science DAILY REPORT #4055

PERIOD COVERED: UT February 21, 2006 (DOY 052)


ACS/HRC 10707

First Mass Measurement of a Planet Found By Microlensing

We will use ACS to determine the mass of the extra-solar planet found in the ongoing microlensing event OGLE-2005-BLG-071. This source will be imaged in V {F555W} and I {F814W} at two epochs, one “very soon” while the event is still significantly magnified, and the other after 5 months when it has returned to baseline. If the centroid does not move, this will demonstrate that the “blended light” detected in the event is “perfectly aligned” {within 15 mas, 1 sigma} with the source, and so is almost certainly the lens. V and I photometry will then permit an estimate of its mass and distance. Since the planet-star mass ratio is already known to be 0.007, this will yield a planet mass. Even if the HST images show that the blended light is not aligned with the source {and so is not from the lens}, the HST observations will still strongly constrain the mass by helping to measure the “microlens parallax”, which when combined with the “angular Einstein radius”, determines the mass. Thus, the observations have a very high probability of success. The observations are time-critical because the first one must be taken while the event is still in progress.

ACS/WFC 10496

Decelerating and Dustfree: Efficient Dark Energy Studies with Supernovae and Clusters

We propose a novel HST approach to obtain a dramatically more useful “dust free” Type Ia supernovae {SNe Ia} dataset than available with the previous GOODS searches. Moreover, this approach provides a strikingly more efficient search-and-follow-up that is primarily pre- scheduled. The resulting dark energy measurements do not share the major systematic uncertainty at these redshifts, that of the extinction correction with a prior. By targeting massive galaxy clusters at z > 1 we obtain a five-times higher efficiency in detection of Type Ia supernovae in ellipticals, providing a well-understood host galaxy environment. These same deep cluster images then also yield fundamental calibrations required for future weak lensing and Sunyaev-Zel’dovich measurements of dark energy, as well as an entire program of cluster studies. The data will make possible a factor of two improvement on supernova constraints on dark energy time variation, and much larger improvement in systematic uncertainty. They will provide both a cluster dataset and a SN Ia dataset that will be a longstanding scientific resource.

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 10596

AGNs with Intermediate-mass Black Holes: A Test of the Black Hole-Bulge Paradigm

The recent progress in the study of central black holes in galactic nuclei has led to a general consensus that supermassive {10^6-10^9 solar mass} black holes are closely connected with the formation and evolutionary history of large galaxies, especially their bulge component. Two outstanding issues, however, remain unresolved. Can central black holes form in the absence of a bulge? And does the mass function of central black holes extend below 10^6 solar masses? Intermediate-mass black holes {10^4-10^6 solar masses}, if they exist, may offer important clues to the nature of the seeds of supermassive black holes. In a first systematic search using the Sloan Digital Sky Survey, we have recently discovered 19 Type 1 AGNs with candidate intermediate-mass black holes that reside in low-luminosity, presumably late-type host galaxies. Follow-up observations with Keck indicate that these objects obey the low-mass extension of the well-known correlation between black hole mass and bulge stellar velocity dispersion. However, very little is known about the host galaxies themselves, including the crucial question of whether they have bulges or not. We propose to obtain ACS/WFC images of this unique sample of AGNs in order to investigate the detailed structural properties of the host galaxies. We are particularly keen to determine whether the hosts contain bulges, and if so, where they lie on the fundamental plane of spheroids compared to the bulges of supermassive black holes. We will also be able to measure an accurate optical luminosity for the AGN, which is an essential ingredient to improve the current mass estimates.

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.

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.

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.


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


10142 – GSAcq(1,2,2) failed to (M2G) due to search radius limit exceeded on FGS-1 @ 052/1259z

The GSAcq(1,2,2) scheduled at 052/12:59:47 – 13:07:52 failed due to search radius limit exceeded on FGS-1. 486 ESB “a05” (search radius limit exceeded) was received at 052/12:50:26. Pre-acquisition OBADs both suceeded. The 2nd OBAD at 052/12:48:56 had attitude correction total (RSS) value of 25.22 arcseconds.

10143 – GSAcq(1,2,2) failed to (T2G) due to search radius limit exceeded on FGS-2 @ 052/1906z

The GSAcq(1,2,2) failed to (T2G) due to search radius limit exceeded on FGS-2. 486 ESB “a05” (search radius limit exceeded) was received at 052/19:11:54. Also (3x) ESB 1805 (T2G_MOVING_TARGET_DETECTED) was received at 052/19:12:17. Pre-acquisition OBADs both suceeded; the GCHALC09 indicator had value 3 for two “successes”. The 2nd OBAD at 052/19:02:18 had attitude correction total (RSS) value of 236.25 arcseconds.



                        SCHEDULED      SUCCESSFUL      FAILURE TIMES 
FGS GSacq               07                    05                 052/1259z 
(HSTAR 10142) 
(HSTAR 10143) 
FGS REacq                08                   08 
OBAD with Maneuver   30                   30 


SpaceRef staff editor.