NASA Hubble Space Telescope Daily Report # 4543

Status Report From: Space Telescope Science Institute
Posted: Friday, February 8, 2008


Continuing to collect World Class Science

PERIOD COVERED: UT February 07, 2007 (DOY 038)


ACS/SBC 10862

Comprehensive Auroral Imaging of Jupiter and Saturn during the International Heliophysical Year

A comprehensive set of observations of the auroral emissions from Jupiter and Saturn is proposed for the International Heliophysical Year in 2007, a unique period of especially concentrated measurements of space physics phenomena throughout the solar system. We propose to determine the physical relationship of the various auroral processes at Jupiter and Saturn with conditions in the solar wind at each planet. This can be accomplished with campaigns of observations, with a sampling interval not to exceed one day, covering at least one solar rotation. The solar wind plasma density approaching Jupiter will be measured by the New Horizons spacecraft, and a separate campaign near opposition in May 2007 will determine the effect of large-scale variations in the interplanetary magnetic field {IMF} on the Jovian aurora by extrapolation from near-Earth solar wind measurements. A similar Saturn campaign near opposition in Jan. 2007 will combine extrapolated solar wind data with measurements from a wide range of locations within the Saturn magnetosphere by Cassini. In the course of making these observations, it will be possible to fully map the auroral footprints of Io and the other satellites to determine both the local magnetic field geometry and the controlling factors in the electromagnetic interaction of each satellite with the corotating magnetic field and plasma density. Also in the course of making these observations, the auroral emission properties will be compared with the properties of the near-IR ionospheric emissions {from ground-based observations} and non thermal radio emissions, from ground-based observations for Jupiter's decametric radiation and Cassini plasma wave measurements of the Saturn Kilometric Radiation {SKR}.

FGS 11210

The Architecture of Exoplanetary Systems

Are all planetary systems coplanar? Concordance cosmogony makes that prediction. It is, however, a prediction of extrasolar planetary system architecture as yet untested by direct observation for main sequence stars other than the Sun. To provide such a test, we propose to carry out FGS astrometric studies on four stars hosting seven companions. Our understanding of the planet formation process will grow as we match not only system architecture, but formed planet mass and true distance from the primary with host star characteristics for a wide variety of host stars and exoplanet masses. We propose that a series of FGS astrometric observations with demonstrated 1 millisecond of arc per-observation precision can establish the degree of coplanarity and component true masses for four extrasolar systems: HD 202206 {brown dwarf+planet}; HD 128311 {planet+planet}, HD 160691 =3D mu Arae {planet+planet}, and HD 222404AB =3D gamma Cephei {planet+star}. In each case the companion is identified as such by assuming that the minimum mass is the actual mass. For the last target, a known stellar binary system, the companion orbit is stable only if coplanar with the AB binary orbit.

NIC1/NIC2/NIC3 8795

NICMOS Post-SAA calibration - CR Persistence Part 6

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=3Ddate/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 i mages. Each observation will need its own CRMAP, as different SAA passages leave different imprints on the NICMOS detectors.

NIC3/WFPC2 11101

The Relevance of Mergers for Fueling AGNs: Answers from QSO Host Galaxies

The majority of QSOs are known to reside in centers of galaxies that look like ellipticals. Numerical simulations have shown that remnants of galaxy mergers often closely resemble elliptical galaxies. However, it is still strongly debated whether the majority of QSO host galaxies are indeed the result of relatively recent mergers or whether they are completely analogous to inactive ellipticals to which nothing interesting has happened recently. To address this question, we recently obtained deep HST ACS images for five QSO host galaxies that were classified morphologically as ellipticals {GO-10421}. This pilot study revealed striking signs of tidal interactions such as ripples, tidal tails, and warped disks that were not detected in previous studies. Our observations show that at least some "elliptical" QSO host galaxies are the products of relatively recent merger events rather than old galaxies formed at high redshift. However, the question remains whether the host galaxies of classical QSOs are truly distinct from inactive ellipticals and whether there is a connection between the merger events we detect and the current nuclear activity. We must therefore place our results into a larger statistical context. We are currently conducting an HST archival study of inactive elliptical galaxies {AR- 10941} to form a control sample. We now propose to obtain deep HST/WFPC2 images of 13 QSOs whose host galaxies are classified as normal ellipticals. Comparing the results for both samples will help us determine whether classical QSOs reside in normal elliptical galaxies or not. Our recent pilot study of five QSOs indicates that we can expect exciting results and deep insights into the host galaxy morphology also for this larger sample of QSOs. A statistically meaningful sample will help us determine the true fraction of QSO hosts that suffered strong tidal interactions and thus, whether a merger is indeed a requirement to trigger nuclear activity in the most luminous AGNs. In addition to our primary science observations with WFPC2, we will obtain NICMOS3 parallel observations with the overall goal to select and characterize galaxy populations at high redshifts. The imaging will be among the deepest NICMOS images: These NICMOS images are expected to go to a limit a little over 1 magnitude brighter than HUDF- NICMOS data, but over 13 widely separated fields, with a total area about 1.5 times larger than HUDF-NICMOS. This separation means that the survey will tend to average out effects of cosmic variance. The NICMOS3 images will have sufficient resolution for an initial characterization of galaxy morphologies, which is currently one of the most active and promising areas in approaching the problem of the formation of the first massive galaxies. The depth and area coverage of our proposed NICMOS observations will also allow a careful study of the mass function of galaxies at these redshifts. This provides a large and unbiased sample, selected in terms of stellar mass and unaffected by cosmic variance, to study the on-going star formation activity as a function of mass {i.e. integrated star formation} at this very important epoch.

WFPC2 11083

The Structure, Formation and Evolution of Galactic Cores and Nuclei

A surprising result has emerged from the ACS Virgo Cluster Survey {ACSVCS}, a program to obtain ACS/WFC gz imaging for a large, unbiased sample of 100 early-type galaxies in the Virgo Cluster. On subarcsecond scales {i.e., <0.1"-1"}, the HST brightness profiles vary systematically from the brightest giants {which have nearly constant surface brightness cores} to the faintest dwarfs {which have compact stellar nuclei}. Remarkably, the fraction of galaxy mass contributed by the nuclei in the faint galaxies is identical to that contributed by supermassive black holes in the bright galaxies {0.2%}. These findings strongly suggest that a single mechanism is responsible for both types of Central Massive Object: most likely internally or externally modulated gas inflows that feed central black holes or lead to the formation of "nuclear star clusters". Understanding the history of gas accretion, star formation and chemical enrichment on subarcsecond scales has thus emerged as the single most pressing question in the study of nearby galactic nuclei, either active or quiescent. We propose an ambitious HST program {199 orbits} that constitutes the next, obvious step forward: high-resolution, ultraviolet {WFPC2/F255W} and infrared {NIC1/F160W} imaging for the complete ACSVCS sample. By capitalizing on HST's unique ability to provide high-resolution images with a sharp and stable PSF at UV and IR wavelengths, we will leverage the existing optical HST data to obtain the most complete picture currently possible for the history of star formation and chemical enrichment on these small scales. Equally important, this program will lead to a significant improvement in the measured structural parameters and density distributions for the stellar nuclei and the underlying galaxies, and provide a sensitive measure of "frosting" by young stars in the galaxy cores. By virtue of its superb image quality and stable PSF, NICMOS is the sole instrument capable of the IR observations proposed here. In the case of the WFPC2 observations, high-resolution UV imaging {< 0.1"} is a capability unique to HST, yet one that could be lost at any time.

WFPC2 11103

A Snapshot Survey of The Most Massive Clusters of Galaxies

We propose the continuation of our highly successful SNAPshot survey of a sample of 125 very X-ray luminous clusters in the redshift range 0.3-0.7. As demonstrated by the 25 snapshots obtained so far in Cycle14 and Cycle15 these systems frequently exhibit strong gravitational lensing as well as spectacular examples of violent galaxy interactions. The proposed observations will provide important constraints on the cluster mass distributions, the physical nature of galaxy-galaxy and galaxy-gas interactions in cluster cores, and a set of optically bright, lensed galaxies for further 8-10m spectroscopy. All of our primary science goals require only the detection and characterization of high-surface-brightness features and are thus achievable even at the reduced sensitivity of WFPC2. Because of their high redshift and thus compact angular scale our target clusters are less adversely affected by the smaller field of view of WFPC2 than more nearby systems. Acknowledging the broad community interest in this sample we waive our data rights for these observations. Due to a clerical error at STScI our approved Cycle15 SNAP program was barred from execution for 3 months and only 6 observations have been performed to date - reinstating this SNAP at Cycle16 priority is of paramount importance to reach meaningful statistics.


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

HSTARS: 11181 - REacq(2,3,2) results in Fine Lock Backup(2,0,2)

During LOS the REacq(2,3,2) scheduled at 038/23:16:48 resulted in fine lock backup (2,0,2). At AOS (23:44:34) stop flags QF3STOPF and QSTOP were flagging. The OBAD at 23:11:45 showed errors of = V1=3D4.02, V2=3D6.07, V3=3D-6.92 and RSS=3D10.04.

                      SCHEDULED      SUCCESSFUL
FGS GSacq               11                 11
FGS REacq               04                 04
OBAD with Maneuver      30                 30


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