NASA Hubble Space Telescope Daily Status Report #4390
Notice: For the foreseeable future, the daily reports may contain apparent discrepancies between some proposal descriptions and the listed instrument usage. This is due to the conversion of previously approved ACS WFC or HRC observations into WFPC2, or NICMOS observations subsequent to the loss of ACS CCD science capability in late January.
HUBBLE SPACE TELESCOPE DAILY REPORT # 4390
– Continuing to collect World Class Science
PERIOD COVERED: UT June 22,23,24, 2007 (DOY 173,174,175)
OBSERVATIONS SCHEDULED
NIC1/NIC2/NIC3 8794
NICMOS Post-SAA calibration – CR Persistence Part 5
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.
NIC2 11157
NICMOS Imaging Survey of Dusty Debris Around Nearby Stars Across the Stellar Mass Spectrum
Association of planetary systems with dusty debris disks is now quite secure, and advances in our understanding of planet formation and evolution can be achieved by the identification and characterization of an ensemble of debris disks orbiting a range of central stars with different masses and ages. Imaging debris disks in starlight scattered by dust grains remains technically challenging so that only about a dozen systems have thus far been imaged. A further advance in this field needs an increased number of imaged debris disks. However, the technical challege of such observations, even with the superb combination of HST and NICMOS, requires the best targets. Recent HST imaging investigations of debris disks were sample-limited not limited by the technology used. We performed a search for debris disks from a IRAS/Hipparcos cross correlation which involved an exhaustive background contamination check to weed out false excess stars. Out of ~140 identified debris disks, we selected 22 best targets in terms of dust optical depth and disk angular size. Our target sample represents the best currently available target set in terms of both disk brightness and resolvability. For example, our targets have higher dust optical depth, in general, than newly identified Spitzer disks. Also, our targets cover a wider range of central star ages and masses than previous debris disk surveys. This will help us to investigate planetary system formation and evolution across the stellar mass spectrum. The technical feasibility of this program in two-gyro mode guiding has been proven with on- orbit calibration and science observations during HST cycles 13, 14, and 15.
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 indvidual 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 11040
Geometric Distortion / Astrometry Closeout
These observations will serve as a final characterization of the geometric distortion and astrometric calibration. The Omega-Cen inner calibration field is used. Filters F300W, F555W, and F814W are observed at 5 roll angles spanning 180 degrees; F218W is observed at a single roll angle.
FGS 11019
Monitoring FGS1r’s Interferometric Response as a Function of Spectral Color
This proosal uses FGS1r in Transfer mode to observe standard single stars of a variety of spectral types to obtain point source interferograms for the Transfer mode calibration library. In specific cases, the calibration star will also be observed in POS mode multiple times with the F583W and F5ND elements to provide the data to verify the stabiligy of the cross filter calibration.
WFPC2 10922
Searching for Signs of a Double Generation of Stars in Galactic Globular Clusters
This proposal has been stimulated by new findings of ours that may have a strong impact on the interpretation of globular cluster {GC} stellar populations. In 2004, based on HST data, we have found that the main sequence of the Galactic globular cluster Omega Centauri is split into two sequences; spectroscopic analysis has shown that the only isochrones which are able to fit the combination of color and metallicity of the bluest of the two sequences were younger and greatly enriched in helium. A number of observational facts, and theoretical evidence suggest that our results on Omega Centauri might represent an extreme case of a phenomenon which has also been at work in other GCs. We have selected the most promising GCs to find out whether this hypothesis is correct, and make a strong case for its likelihood and the value of pursuing it.
NIC2 10893
Sweeping Away the Dust: Reliable Dark Energy with an Infrared Hubble Diagram
We propose building a high-z Hubble Diagram using type Ia supernovae observed in the infrared rest-frame J-band. The infrared has a number of exceptional properties. The effect of dust extinction is minimal, reducing a major systematic tha may be biasing dark energy measurements. Also, recent work indicates that type Ia supernovae are true standard candles in the infrared meaning that our Hubble diagram will be resistant to possible evolution in the Phillips relation over cosmic time. High signal-to-noise measurements of 9 type Ia events at z~0.4 will be compared with an independent optical Hubble diagram from the ESSENCE project to test for a shift in the derived dark energy equation of state due to a systematic bias. Because of the bright sky background, H-band photometry of z~0.4 supernovae is not feasible from the ground. Only the superb image quality and dark infrared sky seen by HST makes this test possible. This experiment may also lead to a better, more reliable way of mapping the expansion history of the universe with the Joint Dark Energy Mission.
WFPC2 10890
Morphologies of the Most Extreme High-Redshift Mid-IR-Luminous Galaxies
The formative phase of the most massive galaxies may be extremely luminous, characterized by intense star- and AGN-formation. Till now, few such galaxies have been unambiguously identified at high redshift, restricting us to the study of low-redshift ultraluminous infrared galaxies as possible analogs. We have recently discovered a sample of objects which may indeed represent this early phase in galaxy formation, and are undertaking an extensive multiwavelength study of this population. These objects are bright at mid-IR wavelengths {F[24um]>0.8mJy}, but deep ground based imaging suggests extremely faint {and in some cases extended} optical counterparts {R~24-27}. Deep K-band images show barely resolved galaxies. Mid-infrared spectroscopy with Spitzer/IRS reveals that they have redshifts z ~ 2-2.5, suggesting bolometric luminosities ~10^{13-14}Lsun! We propose to obtain deep ACS F814W and NIC2 F160W images of these sources and their environs in order to determine kpc-scale morphologies and surface photometry for these galaxies. The proposed observations will help us determine whether these extreme objects are merging systems, massive obscured starbursts {with obscuration on kpc scales!} or very reddened {locally obscured} AGN hosted by intrinsically low-luminosity galaxies.
WFPC2 10877
A Snapshot Survey of the Sites of Recent, Nearby Supernovae
During the past few years, robotic {or nearly robotic} searches for supernovae {SNe}, most notably our Lick Observatory Supernova Search {LOSS}, have found hundreds of SNe, many of them in quite nearby galaxies {cz < 4000 km/s}. Most of the objects were discovered before maximum brightness, and have follow-up photometry and spectroscopy; they include some of the best-studied SNe to date. We propose to conduct a snapshot imaging survey of the sites of some of these nearby objects, to obtain late-time photometry that {through the shape of the light and color curves} will help reveal the origin of their lingering energy. The images will also provide high-resolution information on the local environments of SNe that are far superior to what we can procure from the ground. For example, we will obtain color-color and color-magnitude diagrams of stars in these SN sites, to determine the SN progenitor masses and constraints on the reddening. Recovery of the SNe in the new HST images will also allow us to actually pinpoint their progenitor stars in cases where pre- explosion images exist in the HST archive. This proposal is an extension of our successful Cycle 13 snapshot survey with ACS. It is complementary to our Cycle 15 archival proposal, which is a continuation of our long-standing program to use existing HST images to glean information about SN environments.
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.
NIC2 10849
Imaging Scattered Light from Debris Disks Discovered by the Spitzer Space Telescope around 21 Sun-like Stars
We propose to use the high-contrast capability of the NICMOS coronagraph to image a sample of newly discovered circumstellar disks associated with Sun-like stars. These systems were identified by their strong thermal infrared {IR} emission with the Spitzer Space Telescope as part of the Spitzer Legacy Science program titled “The Formation and Evolution of Planetary Systems” {FEPS, P.I.: M.Meyer}. Modeling of the thermal excess emission from the spectral energy distributions alone cannot distinguish between narrowly confined high-opacity disks and broadly distributed, low-opacity disks. By resolving light scattered by the circumstellar material, our proposed NICMOS observations can break this degeneracy, thus revealing the conditions under which planet formation processes are occuring or have occured. For three of our IR-excess stars that have known radial-velocity planets, resolved imaging of the circumstellar debris disks may further offer an unprecedented view of planet-disk interactions in an extrasolar planetary system. Even non-detections of the light scattered by the circumstellar material will place strong constraints on the disk geometries, ruling out disk models with high optical depth. Unlike previous disk imaging programs, our program contains a well-defined sample of ~1 solar mass stars covering a range of ages from 3 Myr to 3 Gyr, thus allowing us to study the evolution of disks from primordial to debris for the first time. The results from our program will greatly improve our understanding of the architecture of debris disks around Sun-like stars, and will create a morphological context for the existence of our own solar system. This proposal is for a continuation of an approved Cycle 14 program {GO/10527, P.I.: D. Hines}.
WFPC2 10834
The Shell of the Recurrent Nova T Pyx
T Pyx is the only known recurrent nova with a shell. This ‘shell’ is mysterious because it has been resolved into thousands of knots that apparently aren’t expanding. We propose to take a deep F658N image of T Pyx during one orbit to serve as a 12 year baseline from the previous HST WFPC2 images in 1994 and 1995. This much longer baseline will allow us to push down the limits on expansion velocities to ~10 km/s and will allow us to measure the lifetimes of the knots. Also, we expect to discover the expanding inner shell from the last eruption in 1966 which should now have expanded to ~0.9″ in radius. Detailed modeling of the observed line fluxes will give the mass of the individual knots and the shells. The details of the expansion velocities, lifetimes, and masses of the knots will determine the nature of the T Pyx shell; with alternatives being a nova shell, a planetary nebula, stalled shocks in a pre-existing shell, or a cloud ionized by the high luminosity and temperature of the white dwarf. If we can separate out the mass ejected during the 1966 eruption, then we can compare it to the total mass accreted between the 1944 and 1966 eruptions {6.0×10^-6 solar mass} so as to determine whether the white dwarf is gaining or losing mass on average. If the white dwarf is gaining mass, then it must inevitably exceed the Chandrasekhar mass and collapse as a Type Ia supernova, and thus recurrent novae would be shown to be an important component of the solution to the Type Ia progenitor problem.
ACS/SBC 10810
The Gas Dissipation Timescale: Constraining Models of Planet Formation
We propose to constrain planet-formation models by searching for molecular hydrogen emission around young {10-50 Myr} solar-type stars that have evidence for evolved dust disks. Planet formation models show that the presence of gas in disks is crucial to the formation of BOTH giant and terrestrial planets, influences dust dynamics, and through tidal interactions with giant planets leads to orbital migration. However, there is a lack of systematic information on the presence and lifetime of gas residing at planet-forming radii. We will use a newly identified broad continuum emission feature of molecular hydrogen at 1600 Angstrom to search for residual gas within an orbital radius of 5-10 AU around young stars that have evolved beyond the optically thick T Tauri phase. These observations will enable the most sensitive probe to date of remant gas in circumstellar disks, detecting surfaces densites of ~0.0001 g/cm^2, or less than 10^-5 of the theoretical “mininum mass” solar nebula from which our solar system is thought to have formed. Our observations are designed to be synergistic with ongoing searches for gas emission that is being performed using the Spitzer Space Telescope in that the proposed HST observations are ~100 times more sensitive and will have 50 times higher angular resolution. These combined studies will provide the most comprehensive view of residual gas in proto-planetary disks and can set important constraints on models of planet formation.
WFPC2 10807
The knotty jet of He 2-90: An ideal laboratory for studying the formation and propagation of jets in dying stars
Previous WFPC2 observations have led to the serendipitous discovery of an extended, highly-collimated, “pulsed” bipolar jet emanating from a compact planetary nebula, He 2- 90. Subsequently, an average proper motion of the knots in the jet was measured, which together with radial velocities, enabled us to characterise the basic physical properties of the jet. The knotty jet in He 2-90 resembles other prominent examples of pulsed jets in young stellar objects or symbiotic stars, but is probably by far the best example yet of a non-relativistic, symmetric, jet in a “clean” astrophysical environment. The formation {acceleration and collimation} of jets is not fully understood, specially in the case of jets in dying stars. We now propose to re-image He 2-90 with WFPC2 and exploit the factor 3.5 longer time baseline now available from the first-epoch observations in September 1999, in order to measure the proper motion of individual knots in the jet with unprecedented accuracy. These data will enable us to characterise the ejection history of the source, specially deviations from a constant period {latter is related to the binary period of the system}, e.g., due to instabilities in the accretion mechanism. We will also be able to test if the ejection mechanism is symmetric: any deviation in the ejection history of the knots in the opposing jet beams, will indicate a magnetic field structure and/or the accretion disk which is not symmetric across the equatorial plane. We will also carry out deep imaging with the ACS/WFC camera in order to determine the shapes/sizes of a large number of knots. The shapes/sizes of the knots, and changes with distance from the source probe the strength of the magnetic field inside the jet. HRC imaging of the central source and jet on sub-arcsecond scales will be carried out to probe the magnetic field close to the jet source, and deviations from linearity in the jet-beam which may result from instabilities in the magnetic field. These data will allow us to significantly improve our existing 2- dimensional MHD model of the He2-90 jet, and/or provide impetus for new 3-dimensional models.
WFPC2 10800
Kuiper Belt Binaries: Probes of Early Solar System Evolution
Binaries in the Kuiper Belt are a scientific windfall: in them we have relatively fragile test particles which can be used as tracers of the early dynamical evolution of the outer Solar System. We propose to continue a Snapshot program using the ACS/HRC that has a demonstrated discovery potential an order of magnitude higher than the HST observations that have already discovered the majority of known transneptunian binaries. With this continuation we seek to reach the original goals of this project: to accumulate a sufficiently large sample in each of the distinct populations collected in the Kuiper Belt to be able to measure, with statistical significance, how the fraction of binaries varies as a function of their particular dynamical paths into the Kuiper Belt. Today’s Kuiper Belt bears the imprints of the final stages of giant-planet building and migration; binaries may offer some of the best preserved evidence of that long-ago era.
NIC3 10504
Characterizing the Sources Responsible for Cosmic Reionization
Our group has demonstrated the role that massive clusters, acting as powerful cosmic lenses, can play in constraining the abundance and properties of low-luminosity star- forming sources beyond z~6; such sources are thought to be responsible for ending cosmic reionization. The large magnification possible in the critical regions of well- constrained clusters brings sources into view that lie at or beyond the limits of conventional exposures such as the UDF, as well as those in imaging surveys being undertaken with IRAC onboard Spitzer. We have shown that the combination of HST and Spitzer is particularly effective in delivering the physical properties of these distant sources, constraining their mass, age and past star formation history. Indirectly, we therefore gain a valuable glimpse to yet earlier epochs. Recognizing the result {and limitations} of the UDF exposure, we propose a systematic search through 6 lensing clusters with ACS and NICMOS for further z~6-7 sources in conjunction with existing deep IRAC data. Our survey will mitigate cosmic variance and extend the search both to lower luminosities and, by virtue of the NICMOS/IRAC combination, to higher redshift. The goal is to count and characterize representative sources at z~6-10 and to delineate the redshift range of activity for the planning of future observations.
FLIGHT OPERATIONS SUMMARY:
Significant Spacecraft Anomalies: (The following are preliminary reports of potential non-nominal performance that will be investigated.)
HSTARS:
10868 – GSAcq(1,2,1) failed to RGA Hold (Gyro Control)
Upon acquisition of signal at 174/06:56:20, the GSAcq(1,2,1) scheduled at 174/05:39:58 – 05:48:03 had failed to RGA Hold due to (QF1STOPF) stop flag indication on FGS-1. Pre-acquisition OBADs (RSS) attitude correction values not available. Post-acq OBAD/MAP had (RSS) value of 812.49 arcseconds.
10869 – GSAcq(1,2,1) failed to RGA Hold (Gyro Control)
Upon acquisition of signal (AOS) at 175/06:06:35, the GSAcq(1,2,1) scheduled at 175/05:38:12 – 05:46:17 had failed to RGA Hold due to (QF1STOPF) stop flag indication on FGS-1. Pre-acquisition OBAD1 attitude correction value not available due to LOS. OBAD2 had (RSS) value of 8.95 arcseconds. Post-acq OBAD/MAP had (RSS) value of 929.22 arcseconds.
COMPLETED OPS REQUEST:
18110-0 – Configure Kalman Filter for MSS/CSS/Gyro2 monitoring
SCHEDULED SUCCESSFUL
FGS GSacq 19 17
FGS REacq 18 18
OBAD with Maneuver 74 74
COMPLETED OPS NOTES: (None)
SIGNIFICANT EVENTS:
Flash Report: Background Kalman Filter Operation.
The Kalman Filter was reconfigured to an MSS/CSS/Gyro2 configuration at 173/18:22 in support of a long-term KF monitoring test. It will remain in this configuration for approximately a week.
