Status Report

NASA Hubble Space Telescope Daily Report # 4458

By SpaceRef Editor
October 1, 2007
Filed under , ,
NASA Hubble Space Telescope Daily Report # 4458

Notice: Due to the conversion of some ACS WFC or HRC observations into WFPC2, or NICMOS observations after the loss of ACS CCD science capability in January, there may be an occasional discrepancy between a proposal’s listed (and correct) instrument usage and the abstract that follows it.


– Continuing to collect World Class Science

PERIOD COVERED: UT September 271,272,273, 2007 (DOY 28,29,30) OBSERVATIONS SCHEDULED

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

WFPC2 11312

The Local Cluster Substructure Survey {LoCuSS}: Deep Strong Lensing Observations with WFPC2

LoCuSS is a systematic and detailed investigation of the mass, substructure, and thermodynamics of 100 X-ray luminous galaxy clusters at 0.15< z <0.3. The primary goal is to test our recent suggestion that this population is dominated by dynamically immature disturbed clusters, and that the observed mass-temperature relation suffers strong structural segregation. If confirmed, this would represent a paradigm shift in our observational understanding of clusters, that were hitherto believed to be dominated by mature, undisturbed systems. We propose to complete our successful Cycle 15 program {SNAP:10881} which prior to premature termination had delivered robust weak-lensing detections in 17 clusters, and candidate strongly-lensed arcs in 11 of these 17. These strong and weak lensing signals will give an accurate measure of the total mass and structure of the dark matter distribution that we will subsequently compare with X-ray and Sunyaev Zeldovich Effect observables. The broader applications of our project include 1} the calibration of mass-temperature and mass-SZE scaling relations which will be critical for the calibration of proposed dark energy experiments, and 2} the low redshift baseline study of the demographics of massive clusters to aid interpretation of future high redshift {z>1} cluster samples. To complete the all-important high resolution imaging component of our survey, we request deep WFPC2 observations of 20 clusters through the F606W filter, for which wide-field weak-lensing data are already available from our Subaru imaging program. The combination of deep WFPC2 and Subaru data for these 20 clusters will enable us to achieve the science program approved by the Cycle 15 TAC.

WFPC2 11292

The Ring Plane Crossings of Uranus in 2007

The rings of Uranus turn edge-on to Earth in May and August 2007. In between, we will have a rare opportunity to see the unlit face of the rings. With the nine optically thick rings essentially invisible, we will observe features and phenomena that are normally lost in their glare. We will use this opportunity to search thoroughly for the embedded “shepherd” moons long believed to confine the edges of the rings, setting a mass limit roughly 10 times smaller than that of the smallest shepherd currently known, Cordelia. We will measure the vertical thicknesses of the rings and study the faint dust belts only known to exist from a single Voyager image. We will also study the colors of the newly-discovered faint, outer rings; recent evidence suggests that one ring is red and the other blue, implying that each ring is dominated by a different set of physical processes. We will employ near- edge-on photometry from 2006 and 2007 to derive the particle filling factor within the rings, to observe how ring epsilon responds to the “traffic jam” as particles pass through its narrowest point, and to test the latest models for preserving eccentricities and apse alignment within the rings. Moreover, this data set will allow us to continue monitoring the motions of the inner moons, which have been found to show possibly chaotic orbital variations; by nearly doubling the time span of the existing Hubble astrometry, the details of the variations will become much clearer.

NIC2 11219

Active Galactic Nuclei in nearby galaxies: a new view of the origin of the radio-loud radio- quiet dichotomy?

Using archival HST and Chandra observations of 34 nearby early-type galaxies {drawn from a complete radio selected sample} we have found evidence that the radio-loud/radio-quiet dichotomy is directly connected to the structure of the inner regions of their host galaxies in the following sense: [1] Radio-loud AGN are associated with galaxies with shallow cores in their light profiles [2] Radio-quiet AGN are only hosted by galaxies with steep cusps. Since the brightness profile is determined by the galaxy’s evolution, through its merger history, our results suggest that the same process sets the AGN flavour. This provides us with a novel tool to explore the co-evolution of galaxies and supermassive black holes, and it opens a new path to understand the origin of the radio-loud/radio-quiet AGN dichotomy. Currently our analysis is statistically incomplete as the brightness profile is not available for 82 of the 116 targets. Most galaxies were not observed with HST, while in some cases the study is obstructed by the presence of dust features. We here propose to perform an infrared NICMOS snapshot survey of these 82 galaxies. This will enable us to i} test the reality of the dichotomic behaviour in a substantially larger sample; ii} extend the comparison between radio-loud and radio-quiet AGN to a larger range of luminosities.

WFPC2 11218

Snapshot Survey for Planetary Nebulae in Globular Clusters of the Local Group

Planetary nebulae {PNe} in globular clusters {GCs} raise a number of interesting issues related to stellar and galactic evolution. The number of PNe known in Milky Way GCs, 4, is surprisingly low if one assumes that all stars pass through a PN stage. However, it is likely that the remnants of stars now evolving in Galactic GCs leave the AGB so slowly that any ejected nebula dissipates long before the star becomes hot enough to ionize it. Thus there should not be ANY PNe in Milky Way GCs–but there are four! It has been suggested that these PNe are the result of mergers of binary stars within GCs, i.e., that they are descendants of blue stragglers. The frequency of occurrence of PNe in external galaxies poses more questions, because it shows a range of almost an order of magnitude. I propose a Snapshot survey aimed at discovering PNe in the GC systems of Local Group galaxies more distant than the Magellanic Clouds. These clusters, some of which may be much younger than their counterparts in the Milky Way, might contain many more PNe than those of our own galaxy. I will use the standard technique of emission-line and continuum imaging, which easily discloses PNe.

NIC3 11107

Imaging of Local Lyman Break Galaxy Analogs: New Clues to Galaxy Formation in the Early Universe

We have used the ultraviolet all-sky imaging survey currently being conducted by the Galaxy Evolution Explorer {GALEX} to identify for the first time a rare population of low- redshift starbursts with properties remarkably similar to high-redshift Lyman Break Galaxies {LBGs}. These “compact UV luminous galaxies” {UVLGs} resemble LBGs in terms of size, SFR, surface brightness, mass, metallicity, kinematics, dust, and color. The UVLG sample offers the unique opportunity of investigating some very important properties of LBGs that have remained virtually inaccessible at high redshift: their morphology and the mechanism that drives their star formation. Therefore, in Cycle 15 we have imaged 7 UVLGs using ACS in order to 1} characterize their morphology and look for signs of interactions and mergers, and 2} probe their star formation histories over a variety of timescales.  The images show a striking trend of small-scale mergers turning large amounts of gas into vigorous starbursts {a process referred to as dissipational or “wet” merging}. Here, we propose to complete our sample of 31 LBG analogs using the ACS/SBC F150LP {FUV} and WFPC2 F606W {R} filters in order to create a statistical sample to study the mechanism that triggers star formation in UVLGs and its implications for the nature of LBGs. Specifically, we will 1} study the trend between galaxy merging and SFR in UVLGs, 2} artificially redshift the FUV images to z=1-4 and compare morphologies with those in similarly sized samples of LBGs at the same rest-frame wavelengths in e.g. GOODS, UDF, and COSMOS, 3} determine the presence and morphology of significant stellar mass in “pre-burst” stars, and 4} study their immediate environment. Together with our Spitzer {IRAC+MIPS}, GALEX, SDSS and radio data, the HST observations will form a unique union of data that may for the first time shed light on how the earliest major episodes of star formation in high redshift galaxies came about. This proposal was adapted from an ACS HRC+WFC proposal to meet the new Cycle 16 observing constraints, and can be carried out using the ACS/SBC and WFPC2 without compromising our original science goals.

NIC2 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 11079

Treasury Imaging of Star Forming Regions in the Local Group: Complementing the GALEX and NOAO Surveys

We propose to use WFPC2 to image the most interesting star-forming regions in the Local Group galaxies, to resolve their young stellar populations. We will use a set of filters including F170W, which is critical to detect and characterize the most massive stars, to whose hot temperatures colors at longer wavelengths are not sensitive. WFPC2’s field of view ideally matches the typical size of the star-forming regions, and its spatial resolution allows us to measure individual stars, given the proximity of these galaxies. The resulting H-R diagrams will enable studies of star-formation properties in these regions, which cover largely differing metallicities {a factor of 17, compared to the factor of 4 explored so far} and characteristics. The results will further our understanding of the star-formation process, of the interplay between massive stars and environment, the properties of dust, and will provide the key to interpret integrated measurements of star-formation indicators {UV, IR, Halpha} available for several hundreds more distant galaxies. Our recent deep surveys of these galaxies with GALEX {FUV, NUV} and ground-based imaging {UBVRI, Halpha, [OIII] and [SII]} provided the identification of the most relevant SF sites. In addition to our scientific analysis, we will provide catalogs of HST photometry in 6 bands, matched corollary ground-based data, and UV, Halpha and IR integrated measurements of the associations, for comparison of integrated star-formation indices to the resolved populations. We envisage an EPO component.

WFPC2 11033

Full Moon Earth Flats Closeout

Flat field exposures will be obtained by observing the moonlit Earth with the broadband WFPC2 filters F606W and F814W, which saturate in the minimum exposure time on the sunlit Earth. These observations will be used to improve the flats currently in the pipeline and are part of the WFPC2 closeout operations. Because CTE effects are large for star flats and small for full field illumination, Earth flats are the superior technique.

FGS 10930

Mass and Radius of a Near-Chandrasekhar-limit magnetic white dwarf

REJ0317-853 is a unique object. According to our analyses it is the most massive white dwarf ever found, with a mass of 1.35 solar masses, approaching the Chandrasekhar limit. With a period of just 725 seconds it is the most rapidly rotating isolated white dwarf ever found. Moreover, RE J0317-853 is the hottest magnetic white dwarf discovered so far and has a strong magnetic field varying from about 180 to more than 700 MG over the stellar surface. Due to its strong polarization and high mass it has been used to test gravitational theories predicting gravitational birefringence. However, the existing mass and radius determination is indirect and still uncertain and would greatly profit from a high-precision parallax determination with the HST FGS.

NIC3 10909

Exploring the diversity of cosmic explosions: The supernovae of gamma-ray bursts

While the connection between gamma-ray bursts {GRBs} and supernovae {SNe} is now clearly established, there is a large variety of observational properties among these SNe and the physical parameters of these explosions are poorly known. As part of a comprehensive program, we propose to use HST in order to obtain basic information about the supernovae associated with gamma-ray bursts. HST offers the means to cleanly separate the light curves of the GRB afterglow from the supernova, and to remove the contamination from the host galaxy, opening a clear route to the fundamental parameters of the SN. From these observations, we will determine the absolute magnitude at maximum, the shape of the spectral energy distribution, and any change over time of the energy distribution. We will also measure the rate of decay of the exponential tail. Merged with the ground-based data that we will obtain for each event, we will be able to compare our data set to models and constrain the energy of the explosion, the mass of the ejecta and the mass of Nickel synthesized during the explosion. These results will shed light on the apparent variety of supernovae associated with gamma-ray bursts and X-ray flashes, and on the relation between these SNe and other, more common varieties of core-collapse explosions.

ACS/SBC 10872

Lyman Continuum Emission in Galaxies at z=1.2

Lyman continuum photons produced in massive starbursts may have played a dominant role in the reionization of the Universe. Starbursts are important contributors to the ionizing metagalactic background at lower redshifts as well. However, their contribution to the background depends upon the fraction of ionizing radiation that escapes from the intrinsic opacity of galaxies below the Lyman limit. Current surveys suggest escape fractions of a few percent, up to 10%, with very few detections {as opposed to upper limits} having been reported. No detections have been reported in the epochs between z=0.1 and z=2. We propose to measure the fraction of escaping Lyman continuum radiation from 15 luminous z~1.2 galaxies in the GOODS fields. Using the tremendous sensitivity of the ACS Solar- blind Channel, we will reach AB=30 mag., allowing us to detect an escape fraction of 1%. We will correlate the amount of escaping radiation with the photometric and morphological properties of the galaxies. A non-detection in all sources would imply that QSOs provide the overwhelming majority of ionizing radiation at z=1.3, and it would strongly indicate that the properties of galaxies at higher redshift have to be significantly different for galaxies to dominate reionization. The deep FUV images will also be useful for extending the FUV study of other galaxies in the GOODS fields.

WFPC2 10787

Modes of Star Formation and Nuclear Activity in an Early Universe Laboratory

Nearby compact galaxy groups are uniquely suited to exploring the mechanisms of star formation amid repeated and ongoing gravitational encounters, conditions similar to those of the high redshift universe. These dense groups host a variety of modes of star formation, and they enable fresh insights into the role of gas in galaxy evolution. With Spitzer mid-IR observations in hand, we have begun to obtain high quality, multi-wavelength data for a well- defined sample of 12 nearby {<4500km/s} compact groups covering the full range of evolutionary stages. Here we propose to obtain sensitive BVI images with the ACS/WFC, deep enough to reach the turnover of the globular cluster luminosity function, and WFPC2 U-band and ACS H-alpha images of Spitzer-identified regions hosting the most recent star formation. In total, we expect to detect over 1000 young star clusters forming inside and outside galaxies, more than 4000 old globular clusters in >40 giant galaxies {including 16 early-type galaxies}, over 20 tidal features, approximately 15 AGNs, and intragroup gas in most of the 12 groups. Combining the proposed ACS images with Chandra observations, UV GALEX observations, ground-based H-alpha imaging, and HI data, we will conduct a detailed study of stellar nurseries, dust, gas kinematics, and AGN.


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


11005 – FHST OBAD Failure

GSACQ(1,3,3) at 269/04:44:27 acquired in fine lock backup on FGS 1 only, with QF3STOPF and QSTOP flags set on FGS 3 at 04:50:02. No other flags were seen.

REACQ(1,3,3) at 06:17:50 also acquired on FGS 1 only. 11008 – GSAcq (1,2,1) failed to RGA Hold (Gyro Control) @ 272/1319z At AOS 272/13:19:35 observed that GSAcq (1,2,1) scheduled from 272/12:32:14-12:39:44 had failed to RGA Hold (Gyro Control). This was due to QSTOP flag on FGS 1.

OBAD #1 V1 93.63, V2 845.44, V3 557.62 RSS 1017.09

OBAD #2 V1 -2.31, V2 -10.12, V3 6.90, RSS 12.46

OBAD MAP: V1 -553.72, V2 -828.30, V3 342.81, RSS 1053.66

REAcq (1,2,1) scheduled from 272/14:06:47-14:14:17 failed to RGA Hold (Gyro Control) due to QSTOP flag on FGS 1. There were no OBAD’s scheduled prior to the re-acquisition.

OBAD MAP: V1 350.57, V2 583.31, V3 -38.95, RSS 681.67



                        SCHEDULED      SUCCESSFUL 
FGS GSacq                21                  20 
FGS REacq                19                  18 
OBAD with Maneuver       76                  75 


SpaceRef staff editor.