Status Report

NASA Hubble Space Telescope Daily Report # 3389 (part 2)

By SpaceRef Editor
June 23, 2003
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ACS 9401

The ACS Virgo Cluster Survey

We propose the most comprehensive imaging survey to date of low-redshift, early-type galaxies. Our goal is to exploit the exceptional imaging capabilities of the ACS by acquiring deep images — in the SDSS g^ and z^ bandpasses — for 163 E, S0, dE, dE, N and dS0 galaxies in Virgo, the nearest rich cluster. This extraordinary dataset would likely constitute one of the principal legacies of HST, and would have widespread applications for many diverse areas of astrophysics. Our immediate scientific objectives are threefold: {1} measure metallicities, ages and radii for the many thousands of globular clusters {GCs} in these galaxies, and use this information to derive the protogalactic mass spectrum of each galaxy; {2} measure the central luminosity and color profile of each galaxy, and use this information to carry out a completely independent test of the merging hierarchy inferred from the GCs, with the aid of N-body codes that simulate the merger of galaxies containing massive black holes; and {3} calibrate the z^ -band SBF method, measure Virgo’s 3-D structure, and carry out the definitive study of the GC luminosity function’s precision as a standard candle. Our proposed Virgo Cluster Survey will yield a database of unprecedented depth, precision and uniformity, and will enable us to study the record of galaxy and cluster formation in a level of detail which will never be possible with more distant systems.

ACS 9454

The Nature of the UV Continuum in LINERs: A Variability Test

LINERs may be the most common AGNs, and the signposts of accretion onto the massive black holes present in most galaxies. However, the LINER spectrum is the result of UV excitation, and, in at least some LINERs, a nuclear cluster of hot stars, rather than an AGN, dominates the energetics in the UV. Thus, it is still unknown if the UV continuum, or the optical emission lines it excites, have anything to do with an AGN. The demographics and accretion physics of low-luminosity AGNs hinge on this question. We propose to search for variability in a sample of 17 LINERs with compact UV nuclei. Variability can reveal an AGN component in the UV continuum, even when its light is not dominant. We will test systematically the handful of non-definitive reports of UV variability, and potentially quantify the AGN contribution to the UV emission. Variability in all or most objects will be strong evidence that LINERs mark dormant AGNs in most galaxies. Alternatively, a general null detection of variability will suggest that, even in LINERs with additional AGN signatures, the UV continuum is stellar in origin. Contemporaneous monitoring with the VLA/VLBA of 11 objects which have radio cores {five of which we already know are radio-variable} will reveal the relations between UV and radio variations. The UV-variable objects will be targeted for future, better-sampled, monitoring.

ACS/HRC 9379

Near Ultraviolet Imaging of Seyfert Galaxies: Understanding the Starburst-AGN Connection

We propose a near-UV snapshot survey of 101 Seyfert galaxies using ACS/HRC and the filter F330W, a configuration which is optimal to detect faint star forming regions around their nuclei. These images will complement optical and near-IR images available in the HST archive, thus providing a panchromatic atlas of the inner regions of active galaxies, which we will use to study the starburst-AGN connection. The main goals of this proposal are: {1} Determine the frequency of circumnuclear starbursts in Seyferts, down to levels which cannot be observed from the ground; {2} characterize the observational {fluxes, colors, structure, sizes} and intrinsic {luminosities, masses, ages, global star-formation rate} properties of these clusters; {3} derive the luminosity functions of young star clusters around the nucleus of Seyferts and compare these results with those from normal and starburst galaxies to determine their survival rate close to the AGN; {4} address questions about the relation between AGNs and starbursts, like the possible connection between the masses and luminosities of black holes and starbursts, and the implications for the evolution of the black holes and their host galaxy bulges. By adding UV images to the existing optical and near-IR ones, this project will create an extremely valuable database for astronomers with a broad range of scientific interests, from the properties of the AGN to the properties of their host galaxies.

ACS/HRC 9805

OGLE-TR-56b: The Most Interesting Transiting Planet

Our team has recently succeeded in confirming spectroscopically the discovery of the first extrasolar giant planet found in a transit search: OGLE-TR-56b. Its main parameters are: mass = 0.9 Jupiters, size = 1.3 Jupiters. Thus, OGLE-TR-56b appears to be similar to HD 209458b, the only other known transiting giant planet. Unfortunately, our planet radius determination is uncertain due to the very limited precision of the ground-based photometry, and does not allow for a meaningful comparison with theoretical model predictions. We propose HST observations with the ACS-HRC of the main transit of OGLE-TR-56b, which will improve the precision and the accuracy of the planet parameters by close to a factor of 10. In addition, we propose a timing experiment for the planet’s extremely close orbit {1.2-day period, 0.023 AU from the star}, which will allow us to detect the orbital decay and test convection theories.


A NICMOS Study of Merging Nuclei in the Toomre Sequence: Finding Order Amid Chaos

The final death throes of merging spiral galaxy nuclei are hidden behind dusty maelstroms of colliding gas clouds and glaring star formation activity. The dynamically important centers of mass can only be uncovered by imaging at NIR wavelengths and with the high spatial resolution of HST. We propose a near-infrared imaging program to inspect the physical processes of merging at spatial scales of ~100 pc. The Toomre Sequence provides the best sample of merging galaxies for such a study, because it has been studied extensively from the ground, and the global properties are well understood. Our previous Cycle 9 WFPC2 images of the nuclei have revealed a wealth of information on star forming activity and dust, but based on those data alone it is impossible to determine the locations of the current centers of mass. Determining the mass centers and stellar density profiles is important for understanding both the kinematics and the dynamical evolution of the nuclei, and the formation of nuclear density cusps in galaxies. We propose J, H and K band imaging of the nuclei in early and intermediate stage mergers in the Toomre Sequence. Because of the much reduced effect of dust extinction, the near-infrared images are also optimally suited to searches for nuclear rings and bars around the nuclei. Combined with our ongoing Cycle 9 program, these data will provide a detailed view of the structure and evolution of a sequence of merger nuclei.


Completing A Near-Infrared Search for Very Low Mass Companions to Stars within 10 pc of the Sun

Most stars are fainter and less massive than the Sun. Nevertheless, our knowledge of very low mass {VLM} red dwarfs and their brown dwarf cousins is quite limited. Unknown are the true luminosity function {LF}, multiplicity fraction, mass function, and mass-luminosity relation for red and brown dwarfs, though they dominate the Galaxy in both numbers and total mass. The best way to constrain these relations is a search for faint companions to nearby stars. Such a search has several advantages over field surveys, including greater sensitivity to VLM objects and the availability of precise parallaxes from which luminosities and masses can be derived. We propose to complete our four-filter NICMOS snapshot search for companions to stars within 10 pc. With a 10 sigma detection limit of M_J ~ 20 at 10 pc, we can detect companions between 10 and 100 AU that are at least 9 mag fainter than the empirical end of the main sequence and at least 6.5 mag fainter than the brown dwarf Gl 229B. When completed, our search will be the largest, most sensitive, volume-limited search for VLM companions ever undertaken. Our four-filter search will permit unambiguous identification of VLM-companion candidates for follow-up observation. Together with IR speckle and deep imaging surveys, our program will firmly establish the LF for VLM companions at separations of 1-1000 AU and the multiplicity fraction of all stars within 10 pc.


Infrared Photometry of a Statistically Significant Sample of KBOs

While the discovery rate of Kuiper Belt objects is accelerating, the physical study of this new region of the solar system has been slowed by a lack of basic astrophysical data. Photometric observations of the majority of the more than 400 known KBOs and Centaurs are rudimentary and incomplete, particularly in the infrared. The multicolor optical-infrared photometry that exists for a small subset of KBOs often shows significant discrepancies between observations by different observers. Their intrinsic faintness puts them at the practical limits of ground-based systems. In July 2001 we began what will be the largest uniform sample of optical photometry of KBOs with a WFPC2 SNAPSHOT program that will perform accurate photometry at V, R, and I on a sample of up to 150 targets. We seek to greatly enhance the value of this survey by obtaining J and H photometry on the same sample using NICMOS. Combined optical and infrared broad band photometry is a far more powerful tool for physical studies than is either alone. Our sample includes objects that will be observed at thermal infrared wavelengths by SIRTF and will be used with those data to derive the first accurate diameters, albedos, and surface properties for a large sample of KBOs.


NICMOS Post-SAA calibration – CR Persistence Part 2

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.


Paschen-alpha Imaging of a SIRTF-Selected Nearby Galaxy Sample

We propose to carry out a NICMOS snapshot survey in the Paschen-alpha {PAlpha} emission line and H-band of the sample of galaxies being observed at 3.5 — 160 microns as part of SIRTF Nearby Galaxies Survey {SINGS} and a related guaranteed time survey of starburst galaxies. The PAlpha images, accessible only from HST, will be combined with groundbased HAlpha imaging to measure the extinction in the star-forming centers of these galaxies, and obtain robust, extinction- corrected maps of the massive star formation rate {SFR}. The PAlpha data by themselves will provide reliable `extinction- free’ SFRs, and a cross-calibration of the {dust–affected} HAlpha– and UV–based SFRs. The PAlpha–based SFR measurements will extend the SFR-vs.-gas density law {Schmidt–law} to surface densities at least 30 times higher than what is accessible using HAlpha–based SFR measurements alone, bridging the gap between normal galaxies and IR–luminous starbursts. Furthermore, the combination of the HST PAlpha images with the SIRTF images and spectra, as well as ancillary ground–based UBVRIJHK images and GALEX UV images being obtained as part of the SINGS project, will provide a definitive study of the radiative transfer of starlight and dust heating in star–forming galaxies. The processed NICMOS images will be incorporated into the public SINGS Legacy Data Archive, to enable scores of follow-up studies by the astronomical community at large.


The NICMOS Parallel Observing Program

We propose to manage the default set of pure parallels with NICMOS. Our experience with both our GO NICMOS parallel program and the public parallel NICMOS programs in cycle 7 prepared us to make optimal use of the parallel opportunities. The NICMOS G141 grism remains the most powerful survey tool for HAlpha emission-line galaxies at cosmologically interesting redshifts. It is particularly well suited to addressing two key uncertainties regarding the global history of star formation: the peak rate of star formation in the relatively unexplored but critical 1<= z <= 2 epoch, and the amount of star formation missing from UV continuum-based estimates due to high extinction. Our proposed deep G141 exposures will increase the sample of known HAlpha emission- line objects at z ~ 1.3 by roughly an order of magnitude. We will also obtain a mix of F110W and F160W images along random sight-lines to examine the space density and morphologies of the reddest galaxies. The nature of the extremely red galaxies remains unclear and our program of imaging and grism spectroscopy provides unique information

regarding both the incidence of obscured star bursts and the build up of stellar mass at intermediate redshifts. In addition to carrying out the parallel program we will populate a public database with calibrated spectra and images, and provide limited ground- based optical and near-IR data for the deepest parallel fields.


The Origin of Gamma-Ray Bursts

The rapid and accurate localization of gamma-ray bursts {GRBs} promised by a working HETE-2 during the coming year may well revolutionize our ability to study these enigmatic, highly luminous transients. We propose a program of HST and Chandra observations to capitalize on this extraordinary opportunity. We will perform some of the most stringent tests yet of the standard model, in which GRBs represent collimated relativistic outflows from collapsing massive stars. NICMOS imaging and STIS CCD spectroscopy will detect broad atomic features of supernovae underlying GRB optical transients, at luminosities more than three times fainter than SN 1998bw. UV, optical, and X-ray spectroscopy will be used to study the local ISM around the GRB. Chandra spectroscopy will investigate whether the GRB X-ray lines are from metals freshly ripped from the stellar core by the GRB. HST and CTIO infra-red imaging of the GRBs and their hosts will be used to determine whether `dark’ bursts are the product of unusually strong local extinction; imaging studies may for the first time locate the hosts of `short’ GRBs. Our early polarimetry and late-time broadband imaging will further test physical models of the relativistic blast wave that produces the bright GRB afterglow, and will provide unique insight into the influence of the GRB environment on the afterglow.

SNAP 9356

SNAPSHOT survey of the Planetary Nebulae population of the Galactic Bulge

The spectacular structures seen in HST images of planetary nebulae {PNe} are generally accepted as originating from hydrodynamical interactions between stellar winds: the interacting-stellar wind model {ISW}. Traditionally, the shaping is thought to occur after the star becomes hot enough to ionize the PN. But recent HST images indicate that the shaping may occur earlier, and the newer GISW model puts the shaping during the pre-planetary nebula evolution. The relative importance of both models is not known: GISW shaping will account for some fraction of PNe, but estimates range from 15–100 during the PN phase, especially for the youngest PNe. We here propose an HST Snapshot survey of compact PNe in the Galactic Bulge, to test these predictions. The Bulge provides the only PNe population for which progenitor masses are known and nebular ages can be measured. In support of these HST measurements we have already measured velocity fields and emission line fluxes. The survey will give an unbiased sampling of morphologies, and allow evolutionary sequences to be determined to test the ISW versus the GISW model. By-products of the survey will be the determination of nebular masses, diameters and filling factors. We will also obtain the White Dwarf mass distribution in the Bulge, and the initial-final mass function for low-mass stars.

STIS 9608

CCD Bias Monitor – Part 2

Monitor the bias in the 1×1, 1×2, 2×1, and 2×2 bin settings at gain=1, and 1×1 at gain = 4, to build up high-S/N superbiases and track the evolution of hot columns.

STIS 9606

CCD Dark Monitor-Part 2

Monitor the darks for the STIS CCD.

STIS 9504

Probing the Halo and ISM of Low-Redshift Galaxies with Young Supernovae

We propose a Target of Opportunity program to study the halo and ISM of a low-redshift galaxy hosting a bright new supernova {V<= 14}. The primary objectives are to characterize the ionization state, gas-phase abundances, metallicity, and gas kinematics in the ISM and halo of the host galaxy, and, if the properties of the sightline are favorable, in the intervening intergalactic medium. Core-collapse supernovae occuring in galaxies out to the Virgo cluster are the potential targets for this program. The principal spectral region for this study is the short-wavelength ultraviolet {wl <1700Angstrom} using STIS echelle spectra, which provide a comprehensive set of lines to study the hot, warm, and cool phases of the ISM. The HST spectra will be augmented by FUSE TOO observations {900<Lambda<1185Angstrom} of the same object for which we already have allocated time. New core-collapse supernovae, with their strong, nearly featureless UV continua, provide outstanding opportunities to obtain high-quality absorption line spectra of the gas on the line of sight to the SN, but only if the observations are executed within ~1 week of outburst. Our team has the experience and extensive ground-based support to promptly assess the suitability of each newly-discovered supernova for this program and to quickly provide all the necessary data to rapidly execute the observations.

STIS 9708

STIS Pure Parallel Imaging Program: Cycle 11

This is the default archival pure parallel program for STIS during cycle 11.


A Survey for Missing Baryons in Highly Ionized Intergalactic Gas at Low Redshift.

The Space Telescope Imaging Spectrograph (CCD and MA1) was used to observe six additional low-z QSOs with the STIS FUV E140M echelle mode {7 km s^-1 resolution}. Combined with archival data, this will increase the sample redshift path by a factor of ~7 compared to the published data. With the echelle data, we will {1} measure the number of O VI absorbers per unit redshift {dN/dz} and their minimum cosmological mass density with a limiting equivalent width of W_Lambda ~50 mAngstrom , {2} examine whether the O VI absorption arises in photoionized, collisionally ionized, or multiphase gas, and {3} study the dependence of the O VI system properties on environment. In addition to testing this prediction regarding the location of the missing baryons, the data will have applications to many other topics such as low-z LyAlpha absorbers and the physical properties and abundances of gas in the Milky Way halo.


Life Cycles of Radio Galaxies

Now, for the first time, we can probe the duration of nuclear activity and its duty cycle and the relationship between the growth of the bulge {via a starburst} and the growth of the BH {via fueling the AGN}. We have identified a class of powerful radio galaxy which displays both an outer `older’ radio source as well as an inner `younger’ radio source. These `double- doubles’ are sources in which the current radio source is propagating outwards through the relic of the previous epoch of activity. In 3C 236 we found that repeated episodes of star formation and radio ejection were indeed temporally linked. We propose to obtain images of the host galaxies of 4 additional double-double radio galaxies in the NUV with STIS and the R band with ACS/HRC. The proposed HST observations will allow us to determine the existence of young star forming regions in these double-double sources. Follow up imaging and spectroscopy combined with our detailed radio imaging, will allow us to use the double-doubles to address critical questions concerning probe the relationship between star formation and AGN fueling, e.g., – Over what time scales do these processes occur ? — are they short and intense or long and gradual ?

WFPC2 9710

POMS Test Proposal: WFII backup parallel archive proposal

This is a POMS test proposal designed to simulate scientific plans.

WFPC2 9709

POMS Test Proposal: WFII parallel archive proposal

This is the generic target version of the WFPC2 Archival Pure Parallel program. The program will be used to take parallel images of random areas of the sky, following the recommendations of the 2002 Parallels Working Group.

WFPC2 9595


This dark calibration program obtains 3 dark frames every day to provide data for monitoring and characterizing the evolution of hot pixels.

WFPC2 9589

WFPC2 Decontaminations and Associated Observations Pt. 1/3

This proposal is for the monthly WFPC2 decons. Also included are instrument monitors tied to decons: photometric stability check, focus monitor, pre- and post-decon internals {bias, intflats, kspots, & darks}, UV throughput check, VISFLAT sweep, and internal UV flat check.


Significant Spacecraft Anomalies: (The following are preliminary reports of potential non-nominal performance that will be investigated.) None


OPS NOTES EXECUTED: 1113-1 Adjust ACS Error Count Limit @713/1115z (Closed)

                             SCHEDULED     SUCCESSFUL    FAILURE TIMES FGS GSacq                27                        27 FGS REacq                21                        21 FHST Update              52                        52 LOSS of LOCK 


SpaceRef staff editor.