NASA Hubble Space Telescope Daily Report #4331
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 # 4331
– Continuing to collect World Class Science
PERIOD COVERED: UT March 30,31 April 1, 2007 (DOY 089,090,091)
OBSERVATIONS SCHEDULED
NIC1/NIC2/NIC3 8795
NICMOS Post-SAA calibration – CR Persistence Part 6
A new proceedure proposed to alleviate the CR-persistence problem of NICMOS. Dark frames will be obtained immediately upon exiting the SAA contour 23, and everytime 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 11080
Exploring the Scaling Laws of Star Formation
As a variety of surveys of the local and distant Universe are approaching a full census of galaxy populations, our attention needs to turn towards understanding and quantifying the physical mechanisms that trigger and regulate the large-scale star formation rates {SFRs} in galaxies.
NIC1 11063
NICMOS Focus Monitoring
This program is a version of the standard focus sweep used since cycle 7. It has been modified to go deeper and uses more narrow filters for improved focus determination. For Cycle14 a new source has been added in order to accomodate 2-gyro mode: the open cluster NGC1850. The old target, the open cluster NGC3603, will be used whenever available and the new target used to fill the periods when NGC3603 is not visible. Steps: a} Use refined target field positions as determined from cycle 7 calibrations b} Use MULTIACCUM sequences of sufficient dynamic range to account for defocus c} Do a 17- point focus sweep, +/- 8mm about the PAM mechanical zeropoint for each cameras 1 and 2, in 1.0mm steps. d} Use PAM X/Y tilt and OTA offset slew compensations refined from previous focus monitoring/optical alignment activities
WFPC2 11030
WFPC2 WF4 Temperature Reduction #3
In the fall of 2005, a serious anomaly was found in images from the WF4 CCD in WFPC2. The WF4 CCD bias level appeared to have become unstable, resulting in sporadic images with either low or zero bias level. The severity and frequency of the problem was rapidly increasing, making it possible that WF4 would soon become unusable if no work-around were found. Examination of bias levels during periods with frequent WFPC2 images showed low and zero bias episodes every 4 to 6 hours. This periodicity is driven by cycling of the WFPC2 Replacement Heater, with the bias anomalies occurring at the temperature peaks. The other three CCDs {PC1, WF2, and WF3} appear to be unaffected and continue to operate properly. Lowering the Replacement Heater temperature set points by a few degrees C effectively eliminates the WF4 anomaly. On 9 January 2006, the upper set point of the WFPC2 Replacement Heater was reduced from 14.9C to 12.2C. On 20 February 2006, the upper set point was reduced from 12.2C to 11.3C, and the lower set point was reduced from 10.9C to 10.0C. These changes restored the WF4 CCD bias level; however, the bias level has begun to trend downwards again, mimicking its behavior in late 2004 and early 2005. A third temperature reduction is planned for March 2007. We will reduce the upper set point of the heater from 11.3C to 10.4C and the lower set point from 10.0C to 9.1C. The observations described in this proposal will test the performance of WFPC2 before and after this temperature reduction. Additional temperature reductions may be needed in the future, depending on the performance of WF4. Orbits: internal 26, external 1
WFPC2 11029
WFPC2 CYCLE 15 Intflat Linearity Check and Filter Rotation Anomaly Monitor
Intflat observations will be taken to provide a linearity check: the linearity test consists of a series of intflats in F555W, in each gain and each shutter. A combination of intflats, visflats, and earthflats will be used to check the repeatability of filter wheel motions. {Intflat sequences tied to decons, visits 1-18 in prop 10363, have been moved to the cycle 15 decon proposal xxxx for easier scheduling.} Note: long-exposure WFPC2 intflats must be scheduled during ACS anneals to prevent stray light from the WFPC2 lamps from contaminating long ACS external exposures.
WFPC2 11024
WFPC2 CYCLE 15 INTERNAL MONITOR
This calibration proposal is the Cycle 15 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 11023
WFPC2 CYCLE 15 Standard Darks – part 1
This dark calibration program obtains dark frames every week in order to provide data for the ongoing calibration of the CCD dark current rate, and to monitor and characterize the evolution of hot pixels. Over an extended period these data will also provide a monitor of radiation damage to the CCDs.
FGS 10989
Astrometric Masses of Extrasolar Planets and Brown Dwarfs
We propose observations with HST/FGS to estimate the astrometric elements {perturbation orbit semi-major axis and inclination} of extra-solar planets orbiting six stars. These companions were originally detected by radial velocity techniques. We have demonstrated that FGS astrometry of even a short segment of reflex motion, when combined with extensive radial velocity information, can yield useful inclination information {McArthur et al. 2004}, allowing us to determine companion masses. Extrasolar planet masses assist in two ongoing research frontiers. First, they provide useful boundary conditions for models of planetary formation and evolution of planetary systems. Second, knowing that a star in fact has a plantary mass companion, increases the value of that system to future extrasolar planet observation missions such as SIM PlanetQuest, TPF, and GAIA.
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.
NIC1 10859
Precise Measurements of Sgr A Flare Activity
Correlated X-ray and near-IR flare emission from Sgr A , the closest supermassive black hole, contains information about the hydrodynamics, energetics, and accretion behavior of matter within the innermost ten Schwarzschild radii of the hole. We propose HST/NICMOS observations of near-IR flares, in conjunction with already approved obsrevations using XMM-Newton {214 ksec} and CSO {3 nights}, which can make the precise, new measurements necessary to understand the radiation mechanism and low luminosity of Sgr A . HST/NICMOS is required due to its very low and stable background, and its stable, tightly focused PSF, which allow accurate measurement of fainter flares than can be observed using groundbased adaptive optics systems. We will measure the spectral index distribution, the time-averaged flux and duration of flares, and the statistics of flare activity, and will confirm previously reported quasi-periodic variability. These measurements will have far-reaching implications for testing the inverse Compton scattering {ICS} and synchrotron models of low-luminosity flares, for understanding the process of accretion onto and outflow from supermassive black holes, and for constraining the acceleration mechanism of flares and the inferred black hole spin. This knowledge, in turn, will help us understand more generally low-luminosity AGN and X-ray binaries in a very low/quiescent accretion state.
NIC1 10858
NICMOS Imaging of the z ~ 2 Spitzer Spectroscopic Sample of Ultraluminous Infrared
We propose to obtain NICMOS images of the first large sample of high-z ultra-luminous infrared galaxies {ULIRGs} whose redshifts and physical states have been determined with Spitzer mid-IR spectra. The detection of strong silicate absorption and/or PAH emission lines suggest that the these sources are a mixture of highly obscured starbursts, AGNs and composite systems at z=3D2. Although some of the spectra show PAH = emission similar to local starburst ULIRGs, their bolometric luminosities are roughly an order of magnitude higher. One important question is if major mergers, which are the trigger for 95% of local ULIRGs, also drive this enormous energy output observed in our z=3D2 sample. The NICMOS images will allow us to {1} measure surface brightness profiles of z~2 ULIRGs and establish if major mergers could be common among our luminous sources at these early epochs, {2} determine if starbursts and AGNs classified based on their mid-IR spetra would have different morphological signatures, thus different dynamic state; {3} make comparisons with the similar studies of ULIRGs at z ~ 0 – 1, thus infer any evolutionary connections between high-z ULIRGs and the formation of normal, massive galaxies and quasars observed today.
WFPC2 10833
Host Galaxies of Reverberation Mapped AGNs
We propose to obtain unsaturated high-resolution images of 17 reverberation-mapped active galactic nuclei in order to remove the point-like nuclear light from each image, thus yielding a “nucleus-free” image of the host galaxy. This will allow investigation of host galaxy properties: our particular interest is determination of the host-galaxy starlight contribution to the reverberation-mapping observations. This is necessary {1} for accurate determination of the relationship between the AGN nuclear continuum flux and the size of the broad Balmer-line emitting regions of AGNs, which is important in estimating black hole masses for large samples of QSOs, and {2} for accurate determination of the bolometric luminosity of the AGN proper. Through observations in Cycles 12 and 14, we have obtained or will obtain images of 18 of the 35 objects in the reverberation-mapping compilation of Peterson et al. {2004}. These observations revealed that the host-galaxy contribution, even in the higher-luminosity AGNs, is higher than expected and that all of the reverberation- mapped AGNs will have to be observed, not just the lower-luminosity sources; each source is different, and each source is important. Therefore we request time to observe the 17 remaining reverberation-mapped AGNs.
WFPC2 10815
The Blue Hook Populations of Massive Globular Clusters
Blue hook stars are a class of hot {~35,000 K} subluminous horizontal branch stars that have been recently discovered using HST ultraviolet images of the globular clusters omega Cen and NGC 2808. These stars occupy a region of the HR diagram that is unexplained by canonical stellar evolution theory. Using new theoretical evolutionary and atmospheric models, we have shown that the blue hook stars are very likely the progeny of stars that undergo extensive internal mixing during a late helium core flash on the white dwarf cooling curve. This “flash mixing” produces an enormous enhancement of the surface helium and carbon abundances, which suppresses the flux in the far ultraviolet. Although flash mixing is more likely to occur in stars that are born with high helium abundances, a high helium abundance, by itself, does not explain the presence of a blue hook population – flash mixing of the envelope is required. We propose ACS ultraviolet {SBC/F150LP } observations of the five additional globular clusters for which the presence of blue hook stars is suspected from longer wavelength observations. Like omega Cen and NGC 2808, these five targets are also among the most massive globular clusters, because less massive clusters show no evidence for blue hook stars. Because our targets span 1.5 dex in metallicity, we will be able to test our prediction that flash-mixing should be less drastic in metal-rich blue hook stars. In addition, our observations will test the hypothesis that blue hook stars only form in globular clusters massive enough to retain the helium- enriched ejecta from the first stellar generation. If this hypothesis is correct, then our observations will yield important constraints on the chemical evolution and early formation history in globular clusters, as well as the role of helium self-enrichment in producing blue horizontal branch morphologies and multiple main sequence turnoffs. Finally, our observations will provide new insight into the formation of the hottest horizontal branch stars, with implications for the origin of the hot helium-rich subdwarfs in the Galactic field.
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 10798
Dark Halos and Substructure from Arcs & Einstein Rings
The surface brightness distribution of extended gravitationally lensed arcs and Einstein rings contains super-resolved information about the lensed object, and, more excitingly, about the smooth and clumpy mass distribution of the lens galaxies. The source and lens information can non-parametrically be separated, resulting in a direct “gravitational image” of the inner mass-distribution of cosmologically-distant galaxies {Koopmans 2005; Koopmans et al. 2006 [astro-ph/0601628]}. With this goal in mind, we propose deep HST ACS-F555W/F814W and NICMOS-F160W WFC imaging of 20 new gravitational-lens systems with spatially resolved lensed sources, of the 35 new lens systems discovered by the Sloan Lens ACS Survey {Bolton et al. 2005} so far, 15 of which are being imaged in Cycle-14. Each system has been selected from the SDSS and confirmed in two time- efficient HST-ACS snapshot programs {cycle 13&14}. High-fidelity multi-color HST images are required {not delivered by the 420s snapshots} to isolate these lensed images {properly cleaned, dithered and extinction-corrected} from the lens galaxy surface brightness distribution, and apply our “gravitational maging” technique. Our sample of 35 early-type lens galaxies to date is by far the largest, still growing, and most uniformly selected. This minimizes selection biases and small-number statistics, compared to smaller, often serendipitously discovered, samples. Moreover, using the WFC provides information on the field around the lens, higher S/N and a better understood PSF, compared with the HRC, and one retains high spatial resolution through drizzling. The sample of galaxy mass distributions – determined through this method from the arcs and Einstein ring HST images – will be studied to: {i} measure the smooth mass distribution of the lens galaxies {dark and luminous mass are separated using the HST images and the stellar M/L values derived from a joint stellar-dynamical analysis of each system}; {ii} quantify statistically and individually the incidence of mass-substructure {with or without obvious luminous counter- parts such as dwarf galaxies}. Since dark-matter substructure could be more prevalent at higher redshift, both results provide a direct test of this prediction of the CDM hierarchical structure-formation model.
WFPC2 10786
Rotational state and composition of Pluto’s outer satellites
We propose an intricate set of observations aimed at discovering the rotational state of the newly discovered satellites of Pluto, S/2005 P1 and S/2005 P2. These observations will indicate if the satellites are in synchronous rotation or not. If they are not, then the observations will determine the rotational period or provide tight constraints on the amplitude. The other primary goal is to extend the wavelength coverage of the colors of the surface and allow us to constrain the surface compositions of both objects. From these data we will also be able to significantly improve the orbits of P1 and P2, improve the measurement of the bulk density of Charon, and search for albedo changes on the surface of Pluto.
FGS 10612
Binary Stars in Cyg OB2: Relics of Massive Star Formation in a Super-Star Cluster
We propose to make a high angular resolution SNAP survey of the massive stars in the nearby, super-star cluster Cyg OB2. We will use FGS1r TRANS mode observations to search for astrometric companions in the separation range of 0.01 to 1.00 arcsec and in the magnitude difference range smaller than 4 magnitudes. The observations will test the idea that the formation of very massive stars involves mergers and the presence of nearby companions. Discovery of companions to massive stars in this relatively nearby complex will provide guidance in the interpretation of apparently supermassive stars in distant locations. The search for companions will also be important for verification of fundamental parameters derived from spectroscopy, adjustments to main sequence fitting and distance estimations, determining third light contributions of eclipsing binaries, identifying wide colliding wind binaries, studying the relationship between orbital and spin angular momentum, and discovering binaries amenable to future mass determinations. The massive star environment in Cyg OB2 may be similar to the kinds found in the earliest epoch of star formation, so that a study of the role of binaries in Cyg OB2 will help us understand the formation processes of the first stars in the Universe.
NIC2 10603
Multiwavelength Imaging of Edge-on Protoplanetary Disks: Quantifying the Growth of Circumstellar Dust
Young, edge-on circumstellar disks are uniquely valuable laboratories for the study of planet formation. In these objects, the central star is occulted from direct view, significant PSF artifacts are absent, and the disk is clearly seen as a central dust lane flanked by faint disk reflected light. The detailed morphology of these nebulae and its variation with wavelength provide crucial information on the disk internal structure and the properties of its constituent dust grains. A key observable is the slope defining the wavelength dependence of the dust scattering opacity, which becomes shallower when grain growth has taken place; multiwavelength resolved disk images are the key dataset enabling such measurements. Recent analyses of three different edge-on disks have revealed a diversity in their dust properties that is indicative of different degrees of dust grain evolution having taken place in each system. This characterization of disk grain growth, when applied comparatively to a larger sample of these objects, would enable the construction of an evolutionary sequence of young disks at successive stages on the road to planet formation. In pursuit of this goal, we have identified a sample of 15 edge-on disks previously discovered by HST or groundbased telescopes, but for which high fidelity, high spatial resolution images do not yet exist in both the optical and near-infrared. We propose broad- band multicolor imaging with NICMOS of all these targets, and ACS imaging of nine of these targets In combination with existing data, the proposed images will form a complete database of high resolution optical/near-IR images for these 15 disk systems. Scattered light modeling will be used to derive the disk structure and dust properties, yielding results that will be of fundamental importance for our understanding of grain properties during protoplanetary disk evolution.
FLIGHT OPERATIONS SUMMARY:
Significant Spacecraft Anomalies: (The following are preliminary reports of potential non-nominal performance that will be investigated.)
HSTARS:
10762 – GSacq(1,2,2) failed to RGA control. The GSacq(1,2,2) scheduled at 09/19:22:32 failed during LOS. At AOS 19:44:09 flags were present indication the GSacq failed due to receiving stop flag QF1STOPF on FGS 1. The Map at 19:29:58 showed errors of V1=3D-0.27, V2=3D-2.13, V3=3D-4.25, and RSS=3D 4.76
10763 – GSAcq(2,3,3) results in fine lock backup (2,0,2) using FGS2. Upon acquisition of signal at 091/04:09:45, the GSAcq(2,3,3) scheduled at 091/03:43:55 – 03:52:00 had resulted to fine lock backup (2,0,2) using FGS2 due to (QF3STOPF) stop flag indication on FGS3. Pre-acquisition OBADs (RSS) attitude correction values not available due to LOS. Post-acquisition OBAD/MAP not scheduled.
COMPLETED OPS REQUEST: (None)
COMPLETED OPS NOTES: (None)
SCHEDULED SUCCESSFUL FGS GSacq 28 27
FGS REacq 10 10
OBAD with Maneuver 77 77
SIGNIFICANT EVENTS: (None)
