Cycle 10 Abstract catalog (based on Phase I submissions) ================================================================================ Proposal Category: GO Scientific Category: Cosmology ID: 9033 Title: Measuring the mass distribution in the most distant, very X-ray luminous galaxy cluster known PI: Harald Ebeling PI Institution: Institute for Astronomy We propose to obtain a mosaic of deep HST/WFPC2 images to conduct a weak lensing analysis of the mass distribution in the massive, distant galaxy cluster ClJ1226.9+3332, recently discovered by us. At z=0.888 this exceptional system is more X-ray luminous and more distant than both MS1054.4-0321 and ClJ0152.7-1357, the previous record holders, thus providing yet greater leverage for cosmological studies of cluster evolution. ClJ1226.9+3332 differs markedly from all other currently known distant clusters in that it exhibits little substructure and may even host a cooling flow, suggesting that it could be the first cluster to be discovered at high redshift that is virialized. We propose joint HST and Chandra observations to investigate the dynamical state of this extreme object. This project will 1) take advantage of HST's superb resolution at optical wavelengths to accurately map the mass distribution within 1.9 h^-1_ 50 Mpc via strong and weak gravitational lensing, and 2) use Chandra's unprecedented resolution in the X-ray waveband to obtain independent constraints on the gas and dark matter distribution in the cluster core, including the suspected cooling flow region. As a bonus, the proposed WFPC2 observations will allow us to test the results by van Dokkum et al. (1998, 1999) on the properties of cluster galaxies (specifically merger rate and morphologies) at z~ 0.8 from their HST study of MS1054.4-0321. ================================================================================ Proposal Category: GO Scientific Category: Stellar Populations ID: 9034 Title: The Masses and Luminosities of Population II Stars PI: Elliott Horch PI Institution: Rochester Institute of Technology Very little is currently known concerning the mass-luminosity relation (MLR) of Population II stars. However, with the advent of the Hipparcos Catalogue, improved distances to many spectroscopic binaries known to be Pop II systems are now available. After surveying the literature and making reasonable estimates of the secondary masses, we find 13 systems whose minimum separation should be larger than the resolution limit of FGS1. Because of the expected magnitude differences and separations, it is not possible to resolve the systems from the ground. We therefore propose FGS observations of the sample. In combination with the known spectroscopic orbits and Hipparcos distances, these observations will yield up to 26 precise stellar mass determinations of metal-poor stars, if all systems are resolved and the relative orbits are determined. A combination of FGS data and ground-based observations will lead to component luminosities and effective temperatures. This program will allow for a significantly better understanding of the Pop II main sequence, which in turn will lead to better ages and distances of the galactic globular clusters, and a Pop II MLR will be constructed for the first time. ================================================================================ Proposal Category: GO Scientific Category: Solar System ID: 9035 Title: Spatially Resolved Spectroscopy of Uranus and Neptune PI: Erich Karkoschka PI Institution: University of Arizona We propose to use STIS to obtain data cubes for Uranus (Cycle 10) and Neptune (Cycle 11). The spectrum between 290 and 1020 nm is sampled at 2000 wavelengths. The north-south position on the planetary disk is sampled along the slit every 0.05". The east-west position is sampled by successive exposures every 0.05" (longward of 520 nm wavelength) and 0.3" (shortward of 520 nm). Such data have never been obtained. Only HST, with STIS, has the capability to record spatial variations of narrow methane and hydrogen absorption and Raman scattering features. We have obtained such data for Saturn by ground-based observations which permitted a comprehensive understanding of the vertical haze and cloud structure as a function of latitude. Similar improvements are expected from the proposed data for Uranus and Neptune. HST has revealed exciting images of Uranus and Neptune while their quantitative analysis has been slow due to limitations in available filters. Our short, spatially-resolved spectroscopic program will reveal accurate spectral shapes across each WFPC2 filter which then will greatly improve the reliability of interpretations based on hundreds of past anf future WFPC2 images. Similarly, WFPC2 images of Titan required the addition of STIS spectra before the latest improvements in our understanding of its atmosphere were possible. ================================================================================ Proposal Category: GO Scientific Category: Galaxies ID: 9036 Title: An Ultraviolet Spectroscopic Survey of Star-Forming Galaxies in the Local Universe PI: Claus Leitherer PI Institution: Space Telescope Science Institute We propose a comprehensive STIS ultraviolet spectroscopic survey of star- forming galaxies in the local universe. The sample covers a broad range of morphologies, chemical composition, and luminosity. The observations will provide spectral coverage between 1200 and 3100 Angstrom, at a resolution of 100 to 200 kms and S/N of about 30. The data set will allow us to document and quantify the effects of massive stars on the interstellar medium and to infer implications for the evolution of the host galaxies. Specific issues to be addressed are: (i) the relation of interstellar-line profiles to gravity and macroturbulence, and indications for large-scale outflows of the cool gas; (ii) the search for systematic trends of interstellar-line strengths with metallicity, with the goal of calibrating a new metallicity indicator; (iii) the properties of the low- and high-ionization absorption lines of the interstellar medium and their relation to the X-ray emitting gas; (iv) the properties of dust obscuration in star-forming galaxies and its consequences for deriving star-formation rates; (v) studying the star-formation histories and relating the stellar properties to those of the interstellar medium. This data set, while fundamental in its own right, will also be significant as a template for the restframe-ultraviolet of high-z galaxies. We will entirely waive our proprietary rights to give the community immediate access to the data. ================================================================================ Proposal Category: GO Scientific Category: Cool Stars ID: 9037 Title: Imaging the Dust Disk around Epsilon Eridani PI: Mario Livio PI Institution: Space Telescope Science Institute Epsilon Eridani is the closest star to the Sun, around which a planet has been discovered. An asymmetric dust disk around the star has been detected in sub- millimeter observations. The clumps in the disk have been interpreted as resulting from resonant interaction, and the pattern has been predicted to revolve around star at a rate of ~0.7^degrees per year. We propose first epoch observations of the dust disk with STIS, to be followed up in subsequent cycles. These observations will not only reveal what may be the first extra- solar `Kuiper belt', but will also provide a crucial step in the development of observational techniques that can determine the presence and properties of planets, from the visible morphology of the disks around the parent stars. ================================================================================ Proposal Category: GO Scientific Category: Hot Stars ID: 9038 Title: The Evolution of Cataclysmic Variable Stars PI: Thomas Marsh PI Institution: Department of Physics and Astronomy, Southampton University We have discovered that EM Cygni, one of the most well-known cataclysmic variable stars (CVs), is very likely in a triple system with a spatially- unresolved K dwarf. EM Cyg has well measured masses, and the white dwarf's mass of 1.1, M_ shows that it must have come from an AGB star. This, together with considerations of binary evolution, can be used to predict a lower limit to the present-day separation of EM Cyg and the K dwarf of > 18, AU. Ground-based imaging only puts an upper limit on the angular separation of 0.2'', equivalent to < 60, AU at the 300, pc distance of EM Cyg; this does not seriously test the evolutionary prediction. With HST and FGS1R on the other hand, we can resolve a separation 6, AU, providing a direct test of the evolutionary path that leads to CVs, as well as to the Super-Soft X-ray sources widely believed to be the progenitors of Type Ia supernovae. ================================================================================ Proposal Category: GO Scientific Category: Galaxies ID: 9039 Title: Getting to the Core of The Matter: The Inner Region of M15 PI: Bernard McNamara PI Institution: New Mexico State University We propose to measure the velocity dispersion profile within 15 arcseconds of the core of M15 to determine whether the mass distribution in this region is best fit by the presence of a Black Hole or by a more extended distribution of mass. We will test three models of the core region, that is possesses (1) a massive Black Hole, (2) a more extended distribution of neutron stars, or (3) is in the process of core collapse. Our observational data will consist of PC WFPC2 images. Using prior images in the HST archive and newly obtained images, we will compute the core velocity dispersion using proper motions. The expected accuracy of these motions is entirely adequate to test the models mentioned above. ================================================================================ Proposal Category: GO Scientific Category: Quasar Absorption Lines and IGM ID: 9040 Title: Baryons in intermediate redshift (z > 1) OVI absorbers PI: Dieter Reimers PI Institution: Hamburger Sternwarte We propose to search for intervening OVI absorption systems in two further extremely UV bright intermediate redshift QSOs (HS 0747 + 4259, z = 1.9, V = 15.6; HS 0818+2554, z = 1.5, V = 15.4) using the STIS E230M Echelle mode. The scientific aim is to measure the baryonic fraction in the warm-hot intergalactic medium at redshifts 1 <=q z <=q 1.8. Present existing data on HE 0515-4414 taken also with STIS E230M seem to indicate that the baryonic fraction at z = 1.5 is lower by a factor of ~ 15 than the high value found by Tripp et al. (2000) for z < 0.3. Our results need to be confirmed by more lines of sight, and we plan to test hierarchical structure formation models which predict a rapid evolution between z = 1.5 and z = 0. ================================================================================ Proposal Category: GO Scientific Category: Hot Stars ID: 9041 Title: Direct imaging of the progenitors of massive, core- collapse supernovae PI: Stephen Smartt PI Institution: Institute of Astronomy Recent surveys of starforming galaxies in the nearby Universe are discovering significant numbers of supernovae which have massive star progenitors (Types II, Ib and Ic). The extensive HST archive and high-resolution ground-based images of galaxies within ~20 Mpc enables us to resolve and quantify their individual bright stellar content. As massive, evolved stars are the most luminous single objects in a galaxy, the progenitors of core-collapse supernovae should be directly detectable on pre-explosion images. The site of the Type II supernova 1999gi (in NGC3184, ~8 Mpc distant) has been imaged in two colours by HST prior to explosion - it is a young star-forming region, with a resolved, massive stellar population. We request a post-explosion exposure to allow identification of the progenitor star, and its colours. We have deep, high-quality ground-based archive exposures of the pre-explosion region of 1999em (Type II in NGC1673, also at ~8 Mpc distant). We believe we have identified the progenitor as a mid-late G-type supergiant from its VRI colours, however a high-resolution HST image will indicate if this star really is coincident with the SN position at a more secure level. We are assimilating a database of all suitable exposures of nearby galaxies to allow similar future discoveries, and request similar follow-up exposures (as a TOO) if suitable pre-explosion material exists. ================================================================================ Proposal Category: SNAP Scientific Category: Hot Stars ID: 9042 Title: An archive to detect the progenitors of massive, core- collapse supernovae PI: Stephen Smartt PI Institution: Institute of Astronomy Recent surveys of starforming galaxies in the nearby Universe are discovering significant numbers of supernovae which have massive star progenitors (Types II, Ib and Ic). The already extensive HST archive and high-resolution ground- based images of galaxies within ~20 Mpc enables us to resolve and quantify their individual bright stellar content. As massive, evolved stars are the most luminous single objects in a galaxy, the progenitors of core-collapse supernovae should be directly detectable on pre-explosion images. We have detected one Type II progenitor this year, and have proposed a short, companion WFPC2 proposal to confirm this candidate and identify a second. This SNAP proposal aims to increase the amount of WFPC2 multi-colour, pre-explosion imaging data of spirals and high star-formation rate galaxies in the nearby Universe to ~300 galaxies. By doing so we estimate that we may detect 2-3 massive core-collapse progenitors per year. Once we have this high-quality archive in place, we will run the detection program for about 5 years, which will produce a study of the colours of ~10-15 progenitors, revolutionising the present knowledge in the field. ================================================================================ Proposal Category: GO Scientific Category: Cosmology ID: 9043 Title: Cepheid Distances to Early-type Galaxies PI: John Tonry PI Institution: Institute for Astronomy -.07in The HST Key Project on the Extragalactic Distance Scale and the HST project on the ``Calibration of Nearby Type Ia Supernovae'' have greatly improved our knowledge of the Hubble Constant by providing a solid zero point for the Tully-Fisher (TF) relation and Type Ia Supernovae (SNIa). However, severe inconsistencies remain for distance estimators to early-type galaxies such as surface brightness fluctuations (SBF), the planetary nebula luminosity function (PNLF), the fundamental plane (FP), and the globular cluster luminosity function (GCLF). As a result, the distance to the Virgo cluster core remains uncertain by as much as 20 determination is directly affected by a lingering 0.1 mag (5 uncertainty in the photometric calibration of the WFPC2. Resolving these issues is essential not only to firm up the extragalactic distance scale, but also to understand the mass and velocity structure of the local universe. SBF in particular is emerging as the method of choice for mapping local velocity fields to 10,000 kms because it offers an order of magnitude less Malmquist bias than TF, and SNIa are too rare to study large scale flows effectively. This project will tighten the photometric calibration of the WFPC2, and provide a solid Cepheid calibration for SBF and PNLF. ================================================================================ Proposal Category: GO Scientific Category: Stellar Populations ID: 9044 Title: The Stellar Population of UGCA 292, An Extreme Low Metallicity Galaxy PI: Liese van Zee PI Institution: Herzberg Institute of Astrophysics As the third lowest metallicity galaxy known, UGCA 292 provides a unique opportunity to investigate the evolutionary status of extremely metal--poor, gas--rich, star--forming galaxies. UGCA 292 is sufficiently nearby (3.1 Mpc), that it is possible to resolve the stellar population with HST. The proposed observations will enable us to investigate the stellar population of this relatively unevolved galaxy to determine if the low metallicity and high gas mass fraction are indicative of a newly formed galaxy. The detection of an intermediate age stellar population in UGCA 292 will definitively prove that it is possible to have galaxies which are gas--rich and metal--poor, yet have extended star formation histories. Alternatively, the lack of an intermediate age stellar population in UGCA 292 will support the hypothesis that there is no single epoch of galaxy formation, and that some low mass galaxies have delayed formation for almost a Hubble time. ================================================================================ Proposal Category: GO Scientific Category: AGN/Quasars ID: 9045 Title: The Relationship Between Radio Luminosity and Radio-Loud AGN Host Galaxy Properties PI: Chris Willott PI Institution: University of Oxford We propose a large program aimed at determining the relationship between the properties of the host galaxies of radio-loud AGN and their radio luminosities. Previous studies in this area with the HST have concentrated on the 3C sample which shows a tight correlation between luminosity and redshift, such that evolutionary effects cannot be distinguished from those depending upon radio luminosity. Our sample of 46 radio galaxies at z ~ 0.5 comes from four complete, low-frequency-selected samples of radio sources with differing flux limits. Thus the total sample spans an unprecedented three orders of magnitude in radio luminosity at a fixed redshift interval. These observations will probe the relationship between the radio sources, their host galaxies and supermassive black holes. With 2D-modelling of the radio galaxies we will derive morphologies and scalelengths to determine if all radio-loud AGN reside in giant ellipticals and follow the Kormendy relation exhibited by low- redshift, radio-quiet ellipticals. ================================================================================ Proposal Category: GO Scientific Category: Galaxies ID: 9046 Title: Black Holes and Bars: A Recipe for Making Bulges? PI: Martin Bureau PI Institution: Sterrewacht Leiden We propose to obtain WFPC2 multi-color images and STIS emission line spectroscopy of the nuclear regions of 6 edge-on barred spiral galaxies spanning a range of bulge morphologies and bar strengths. Our goal is to quantify the amount of vertical heating in the nuclei, and to test whether or not bars are indeed destroyed and create a bulge if enough mass is accumulated in their centers. Edge-on galaxies provide a unique tool to study the structure and dynamics of barred disks rapidly and extensively, and we have already obtained extensive ground-based data for all our targets. The high spatial resolution of HST is crucial for our project as the efficiency of bar- driven processes is determined by the galaxies' nuclear properties. Our images will yield the nuclear cusp slope and will allow us to determine the conditions under which bars can survive. Color information is required to correct for internal dust extinction, identify population gradients, and evaluate the rate at which disk stars migrate into bulges. STIS will be used to probe the kinematics of the nuclear gas disks and to weigh any unresolved massive point mass (black hole), providing a direct test of bar dissolution scenarios. We will use line-ratio diagnostics to study the physical conditions of the nuclear gas and determine the importance of bar-induced shocks and nuclear spirals for inflow. ================================================================================ Proposal Category: GO Scientific Category: Cool Stars ID: 9047 Title: The densely spotted photospheres of active cool stars PI: Andrew Cameron PI Institution: University of St Andrews Rapidly rotating main-sequence stars are so heavily mottled by starspots that rotational modulation of their light may amount to 0.1 magnitude or more. Over the last decade or so, the spatial distributions of the largest starspot groups have been mapped on many active stars using Doppler imaging methods applied to ground-based echelle spectroscopy. In rapidly rotating young main- sequence stars with ages comparable to the Pleiades, Doppler images seldom show more than 10 methods such as TiO band-strength analysis and broad-band optical and near-IR photometry, however, indicate that 20 active stars' surfaces are occupied by spots. The discrepancy can be resolved by requiring the brighter regions of an active stellar surface to be packed with a high density of dark spots, too small to be resolved in Doppler images. Here we propose to measure the packing fraction and size distribution of small starspots on the inner face of the G2/3V primary of the eclipsing binary SV Cam (= HD 44982). We will observe three primary eclipses at the exquisite photometric precision (1.3* 10^-4 mag RMS with time resolution 50s) attainable by using STIS as a bright-star photometer. Starspots with radii as small as 15000 km will be detected as marginally-resolved, 5Sigma fluctuations in the eclipse profile as the dark K5 secondary scans across the disk of the primary. ================================================================================ Proposal Category: GO Scientific Category: Cool Stars ID: 9048 Title: Boron Constraints on Slow Mixing in Low Mass Stars PI: Constantine Deliyannis PI Institution: Indiana University, Department of Astronomy The atomic and nuclear characteristics of the light elements Li, Be and B make their photospheric abundances ideal tracers of internal physical processes in stars. Both Li and Be have been heavily utilized to this end since their diminished abundances are a direct result of the extent of internal slow mixing between surface and interior layers, as we have shown with our ground- based data. Boron provides a fresh and special probe because it survives to greater depths inside stars than does Li or Be, and can thus uniquely reveal the depth of mixing. We propose to observe B in stars with very large depletions of Li and Be, i.e. stars which have been the most seriously affected by mixing. Previously, we have found one star in which B might be slightly depleted; new observations are needed to establish whether or not B depletion really occurs in stars, and if yes, how much. Our published detailed stellar models agree remarkably well with the correlated depletion of Li and Be. Similar models imply that the Big Bang ^7Li abundance has been depleted, up to 0.3dex according to ^6Li data. However, such models do not deplete B. It is thus imperative (for improved knowledge of both, stellar interiors and cosmology) to establish whether low mass stars deplete B, and thus the degree to which such models are or are not realistic. In low mass dwarfs, B can only be observed from space, using HST/STIS. ================================================================================ Proposal Category: GO Scientific Category: Cool Stars ID: 9049 Title: Boron in G64-12: Higher Big Bang Lithium or Signature of the Nu-Process? PI: Constantine Deliyannis PI Institution: Indiana University, Department of Astronomy The extremely metal-poor ( Fe/H ~ -3.3 ) star G64-12 shows a remarkable lithium (Li) abundance that is about 2 times larger than those seen in other warm metal-poor stars, from which the Big Bang Li abundance is inferred. This star's enhanced Li has resulted from either a) Galactic Li enrichment from a lower Big Bang value, or b) stellar depletion from a higher Big Bang value, with significant cosmological implications. We argue against two of the three prominent mechanisms of Galactic Li enrichment, leaving the theoretical Nu-process in Type II supernovae as the sole viable mechanism. This mechanism's crisp signature is the concomitant production of copious amounts of boron (B); if the Nu-process enriched the material out which G64-12 formed with the extra Li observed today, then this star should also exhibit a large detectable B overabundance. B in G64-12 can only be observed from space, using HST/STIS. If this star's STIS-based B abundance lies above the established B- Fe trend, this would be the first observational evidence for the Nu-process. But if its B abundance lies near the B-Fe trend, this would provide direct evidence that G64-12 is an elusive fossil of a Big Bang Li abundance about 0.3 dex above currently favored values, providing consistency in standard Big Bang Nucleosynthesis between Li and D (but not ^4He). EITHER RESULT would be of fundamental importance to Astronomy. ================================================================================ Proposal Category: GO Scientific Category: ISM and Circumstellar Matter ID: 9050 Title: Outflow Collimation in Bipolar Symbiotic Nebulae PI: Bruce Balick PI Institution: University of Washington Flow collimation in evolved stars is neither expected nor understood. Classical theories of stellar evolution do not predict and cannot explain this bipolarity. More exotic concepts (binary interactions, spun-up atmospheres, poloidal or toroidal magnetized winds) have been proposed, but observations are yet to verify or falsify any of their predictions. We propose to probe the near-nuclear morphology and kinematics of four bright, low-extinction targets whose large-scale structure is highly bipolar. Our goal is to provide a detailed description of the circumnuclear outflows, to uncover the physical structure and nature of the collimator, and to evaluate the speculative collimation mechanisms. The bright nucleus has hampered efforts to explore the nebular collimators that lie close to the star, so we'll use STIS to disperse the nuclear light and, thus, to avoid its glare. A secondary goal is to obtain second-epoch WFPC2 images of all targets. The outflow speeds predict readily measurable proper motions of >~2 PC pix in 3 yr at distances of 0.5--1 kpc. ================================================================================ Proposal Category: GO Scientific Category: Quasar Absorption Lines and IGM ID: 9051 Title: Identifying Damped Lyman-alpha Galaxies at z~1 PI: Robert Becker PI Institution: University of California, Davis Damped Lyman-alpha absorption systems contain the bulk of the neutral gas in the Universe in the redshift range z = 0.5 - 5 yet the nature of the galaxies responsible for the absorption is not well understood. Only recently have we found more than a handful of damped absorbers at redshifts z < 1.5. Using the FIRST Bright Quasar Survey (FBQS), with over a 1000 quasars, we have undertaken a survey to build a complete picture of the nature of the galaxies responsible for damped Lyman-alpha absorption systems at z~1 and to double the sample size at this redshift. The FBQS provides the first large, well defined, unbiased sample to use in these studies. STIS spectroscopy of candidate damped absorption systems at z < 1.7 is required to accurately measure their HI column densities and confirm which are damped. A complementary ground-based imaging and spectroscopic program is underway at Keck Observatory to identify and characterize the galaxies associated with the absorption systems. ================================================================================ Proposal Category: GO Scientific Category: Solar System ID: 9052 Title: A Global Search for Alteration Minerals on Mars PI: James Bell PI Institution: Cornell University -0.5cm We propose to perform high spatial resolution and moderate spectral resolution 3000 Angstrom to 5700 Angstrom STIS long-slit imaging spectroscopy of Mars, to search for and globally map the presence of iron- bearing minerals that are diagnostic of specific climatic conditions. STIS measurements would be obtained by push-broom scanning the 0.2 " slit across the planet during four separate visits spaced ~90degrees apart in Martian longitude. These hyperspectral STIS image cubes will be complemented by near- simultaneous WFPC2 UV-VIS imaging that will allow us to quantify the effects of water ice clouds or other aerosols on our STIS spectra. These STIS data will provide the ability to detect and map small abundances (~1 jarosite K,Na,H_3OFe_3(SO_4)_2(OH)_6, goethite (AlphaFeOOH), hematite (alphaFe_2O_3), and other ferric and ferrous phases. These minerals are formed under specific environmental conditions, and some are potential sinks for Martian atmospheric volatiles. Our search will be conducted at a spatial scale comparable to existing spacecraft orbital spectroscopy data (~15-20 km/pixel) and in a wavelength region not sampled by existing or planned Mars spacecraft instrumentation. These observations also provide complementary measurements in support of current and future NASA Mars exploration missions. We require these observations to be scheduled near opposition (June-July 2001) in order to maximize spatial resolution. ================================================================================ Proposal Category: GO Scientific Category: Stellar Populations ID: 9053 Title: The Late Evolution of Low-Mass Stars: a Deep UV Color- Magnitude Diagram of M32 PI: Thomas M. Brown PI Institution: Goddard Space Flight Center We propose to construct a deep far-UV color-magnitude diagram (CMD) of the hot stellar population in the center of M32 (NGC221). Our previous Cycle 7 near- UV STIS observations of the M32 core resolved ~8000 stars in a single bandpass. While these observations provided no color information, they nonetheless showed conclusively that hot ( T_eff > 8500 K) horizontal branch (HB) stars exist in M32. Moreover, the near-UV luminosity function showed a surprising lack of post-asymptotic giant branch (post-AGB) stars, indicating that they evolve much more rapidly than expected from canonical theory. Obtaining color information is the vital next step to extending this analysis. A CMD for a statistically large sample of evolved stars in M32 will provide fundamental information on post-red giant branch evolution that is not obtainable from Galactic globular clusters (because of too few stars) or from the Galactic field (because distance uncertainties dominate the errors). We aim to address the following questions: 1) Do hot HB stars have high helium abundance, as predicted by some models of elliptical galaxy chemical evolution? 2) How does the rate of post-AGB evolution differ from theoretical expectations, and what does this tell us about mass-loss on the AGB? 3) What is the mass and temperature distribution on the HB of M32? 4) What are the relative lifetimes of the HB and post-HB phases? ================================================================================ Proposal Category: GO Scientific Category: Galaxies ID: 9054 Title: Star Formation Triggers and Chemical Reprocessing in I Zw 18 PI: Thomas M. Brown PI Institution: Goddard Space Flight Center I Zw 18 is a blue compact galaxy (BCD) with the smallest known abundance of heavy elements yet observed. Although it is currently undergoing an intense period of star formation, debate continues to focus on the presence of any older generations of stars in this system. If its star formation history is truly restricted to the last ~50 Myr, the existence of I Zw 18 demonstrates that the formation of galaxies can be delayed until the present epoch. This galaxy may represent a local template for the young galaxies that will be observed with NGST at high redshift, and as such it is essential that we understand its evolutionary status. Narrow-band imaging and spectroscopy have focused on the ionized gas in this galaxy. Broad-band imaging has resolved the brighter stellar populations, but due to the uncertain distance of I Zw 18 and its high level of crowding, interpretation of this imaging has been disputed. We propose a spatially resolved far-UV spectroscopic map of this critically important galaxy. Our data will investigate how star formation propagates across a starbursting galaxy, determine if heavy elements have been incorporated into the young hot stars or instead have been blown out of the galaxy, extend our understanding of mass loss and stellar winds to very low metallicity, and create a template for metal-poor starbursts observed at high redshift. ================================================================================ Proposal Category: GO Scientific Category: Star Formation ID: 9055 Title: Direct Detection of an Extrasolar Planet in Reflected Light PI: David Charbonneau PI Institution: Harvard-Smithsonian Center for Astrophysics HD 209458 b is the first extrasolar planet known to transit the disk of its parent star. Precise measurement of both the photometric transit curve and the radial velocity orbit has allowed for an accurate estimation of the mass, radius, average density and surface gravity. We propose to detect directly the gas giant planet orbiting HD 209458 in reflected light by observing the secondary eclipse, i.e. when the planet is occulted by the star. We will use STIS to disperse the stellar flux over a large number of detector pixels. The photometric signal is produced by summing the counts over a desired band. For each of six bands spanning the UV to the near-IR, we will obtain sufficient precision either to detect the planet, or to limit its geometric albedo in each band to less than 0.2. Combining data at all wavelengths, our detection threshold for the average geometric albedo will be 0.08. These data span the wavelengths over which the majority of the stellar flux is emitted. Thus we will quantify the net energy deposited into the planet, the key remaining unknown in comparing the measured planetary radius to theoretical models of its structure and evolutionary history. Furthermore, the measured wavelength- dependent albedo will provide stringent constraints on the numerous atmospheric models for these objects. We should be able to identify the dominant scattering sources, such as Rayleigh scattering and atmospheric silicates. ================================================================================ Proposal Category: GO Scientific Category: Solar System ID: 9056 Title: Spectroscopic Imaging of the Atmosphere of Callisto PI: Paul D. Feldman PI Institution: The Johns Hopkins University We propose to obtain long-slit imaging ultraviolet spectra of Callisto, using STIS with the G140L grating, to study the interaction of the Jovian plasma environment with the tenuous carbon dioxide atmosphere of this icy satellite. This spectral range is rich in emissions of CO, ionC1, ionC2, and ionO1 characteristic of CO_2 atmospheres. Recent Galileo measurements of atmospheric CO_2 infrared limb emission and the plasma density and magnetic field in the vicinity of Callisto suggest that Callisto should show emission brightness comparable to Europa and Ganymede, both of which have been successfully imaged in ultraviolet ionO1 emission by STIS. ================================================================================ Proposal Category: SNAP Scientific Category: AGN/Quasars ID: 9057 Title: Host Galaxies of Obscured QSOs Identified by 2MASS PI: Dean C. Hines PI Institution: The University of Arizona We propose a WFPC2 snapshot survey of red QSOs discovered in The Two Micron All Sky Survey (2MASS) to investigate the detailed properties of their host galaxies. This large, possibly dominant, population of QSOs in the local universe has been previously overlooked because reddening by (intrinsic) obscuration along our line of sight causes their colors to be too red for identification by traditional ``UV-excess'' techniques. Their near-IR colors are similar to PG-type (UV-excess) QSOs, but it is far from certain whether they are indeed from the same parent population or represent a completely new class of QSO. Hints from our polarimetry survey suggest that they may simply be highly inclined PG-type QSOs. Alternatively, they may represent objects with high dust cover from an interaction similar to that seen in the Ultra- and Hyperluminous Infrared Galaxies (ULIRGs & HIGs). Regardless, the strong attenuation of the nuclear UV/optical light affords us with the unique opportunity to investigate the optical properties of QSO host galaxies without the pitfalls encountered while observing QSOs whose blinding nuclear emission often completely overwhelms the host galaxy, even in HST images. The snapshot images will form a comprehensive census, and strong legacy database, of the 2MASS QSO host galaxies that can be compared directly with previous HST imaging studies of PG-type QSOs, ULIRGs and HIGs. ================================================================================ Proposal Category: GO Scientific Category: Stellar Populations ID: 9058 Title: Trigonometric Parallax of the Globular Cluster 47 Tucanae PI: Ivan King PI Institution: University of California, Berkeley Using high-precision astrometric techniques that we have developed and demonstrated, we propose to measure the trigonometric parallax of 47 Tuc, which is about one quarter milliarcsec, to an accuracy of 10 repeating a field that was observed in 1995, we will measure the secular motion of the cluster stars with respect to the SMC background with sufficient accuracy that the parallax can be measured directly from the displacements within Cycle 10. Constraints of orientation, and the shape of the WFPC2 footprint, require that we take images at 3-month intervals, rotating 90 degrees each time. This project will have an important impact on the globular-cluster distance scale, and through it on the distance scale and age of the Universe. By doing so it will demonstrate the astrometric power of HST par excellence. ================================================================================ Proposal Category: GO Scientific Category: Solar System ID: 9059 Title: UV/Visible Spectroscopy of Asteroid 762 Pulcova and its Newly-discovered Moon PI: William Merline PI Institution: Southwest Research Institute We propose to acquire separate, comparative, and simultaneous spectra of asteroid 762 Pulcova and its satellite. We will compare our results with those we obtain in an identical program approved in Cycle 9 for 45 Eugenia and its moon. We discovered both of these moons using ground-based adaptive optics --- Eugenia in 1998, but Pulcova only in the last year. We can now compare two systems that both have primaries of the relatively uncommon F-like spectral class. We will use the high-spatial-resolution and UV-capabilities of STIS to obtain medium-resolution spectra over the range 2900--10300 Angstrom, using only two grating settings, on a single HST orbit. We will determine whether the surface compositions are similar or different in the parent-satellite pair and test hypotheses concerning satellite production mechanisms. Our fits to the orbits yield a surprisingly low density for Eugenia of 1.2 g cm^-3, but that of Pulcova is 50 F-type spectra are similar to the common C-types, but differ by the lack of a UV-band or UV-dropoff and by subtle, but measurable differences in the spectral slope. Both the UV-region and the existence of subtle absorption features in the near-IR (~ 9000 Angstrom) are diagnostic of the specific differences between F-, C-, and (Bus') X-class. HST is required because ground-based adaptive optics is not available in the UV and cannot yet provide adequate resolution in the visible. ================================================================================ Proposal Category: SNAP Scientific Category: Solar System ID: 9060 Title: Photometry of a Statistically Significant Sample of Kuiper Belt Objects PI: Keith Noll PI Institution: Space Telescope Science Institute accelerating, the physical study of this new region of the solar system has been retarded by a lack of basic astrophysical data. Photometric observations of the majority of the more than 330 known KBOs and Centaurs are rudimentary and incomplete. The multicolor photometry that exists for a small subset of ~30 KBOs often shows significant discrepancies between observations by different observers. The intrinsic faintness of KBOs puts them at the practical limits of ground-based systems. We propose to propel the physical study of KBOs forward by performing accurate photometry at V, R, and I on a sample of up to 150 KBOs. Our sample is made up of objects that will be observed at thermal infrared wavelengths by SIRTF and will be used with those data to derive the first accurate diameters and albedos for a large sample of KBOs. ================================================================================ Proposal Category: GO Scientific Category: Stellar Populations ID: 9061 Title: A Census of Planets in the Globular Cluster M22 and the Galactic Bulge PI: Kailash C. Sahu PI Institution: Space Telescope Science Institute We propose a program of intensive monitoring of the globular cluster M22 and its background Galactic bulge field, using both WFPC2 and simultaneous parallel STIS imaging. In an earlier pilot program to look for microlensing events due to M22, we detected one long-duration event (lens mass of 0.25 M_solar), and 11 candidate short-duration (<0.4 days) events corresponding to lens masses of <0.25 Mjup. This suggests the startling possibility that a non-negligible fraction of the cluster mass resides in free-floating, sub-Jupiter mass objects. However, each of the 11 events was seen only as a single brightening, due to the wide spacing of the observations. In order to follow up on this potentially important discovery, we propose to observe two fields in the core of M22 continuously with WFPC2 over a 7-day interval (92 orbits), followed by an additional 31 orbits spaced out over the ensuing 13 days. Based on the pilot study, we expect to detect 10--25 short-duration microlensing events, which will be well sampled and will yield lens masses. We will simultaneously observe a bulge field with STIS imaging, in order to detect planetary transits. Depending on the frequency of planets and its metallicity dependence, we should detect 3--15 planetary transits among the bulge stars. Byproducts will be a search for planets around the M22 stars, and a census of variable stars and binaries in both the cluster and the bulge. ================================================================================ Proposal Category: GO Scientific Category: Solar System ID: 9062 Title: Observations of Comet Borrelly to Support the New Millennium/DS1 Flyby Occurring 23 September 2001 PI: Alan Stern PI Institution: Southwest Research Institute The New Millenium Program (NMP) Deep Space 1 asteroid-comet flyby mission is now en route to comet 19P/Borrelly for a late September 2001 flyby. DS1 carries particle and field instruments, a monochrome imager, and an IR imaging spectrometer; its UV spectrometer is inoperable. On behalf of the DS1 Science Team, we request STIS imagery and spectroscopy of comet Borrelly at the time of the DS1 encounter in order to provide both support science and context for the flyby datasets; the proposed Borrelly observations will also reveal important new information relating to the intriguing carbon-depletion in this bright, well-known comet with an origin in the Kuiper Belt. ================================================================================ Proposal Category: GO Scientific Category: Hot Stars ID: 9063 Title: Optical Counterparts of Isolated Neutron Stars PI: Marten van Kerkwijk PI Institution: Utrecht University There has been gradual recognition of neutron stars as laboratories to test our understanding of both quantum chromodynamics (QCD) and quantum electrodynamics (QED). Specifically, the measurement of radii of neutron stars can test QCD at high density. This is being realized through intensive X-ray observations of bright nearby neutron stars. However, the natures of these important sources are not clear and to this end we propose a simple proper motion program as a means to obtain their ages and potential association with star-forming regions. One of the sources is RX J0720.4-3125 which has been argued to be an old magnetar --- a highly magnetized neutron star --- and thanks to its high count rate is already a choice object for X-ray missions. Magnetars, with their extreme magnetic field strengths, are excellent laboratories for testing out some expectation of QED. We show how UV observations can be combined with optical and X-ray observations to demonstrate the magnetar nature of the source. The other sources are the brightest of the nearby neutron stars that currently lack optical identifications. For these we will first detect them and then perform accurate astrometry so that future observations will yield birth locations. ================================================================================ Proposal Category: GO Scientific Category: Star Formation ID: 9064 Title: HI Detection of an Extra-Solar Planetary Atmosphere PI: Alfred Vidal-Madjar PI Institution: Institut d'Astrophysique de Paris, CNRS The extra-solar planet discovered around HD 209458 is the unique one also detected through occultation. During its transit, we will obtain spectra of the HI and DI Lyman-Alpha line at 1215Angstrom . The extremely extended planetary exosphere is expected to produce an absorption line against the stellar chromospheric Lyman-Alpha emission. Because hydrogen is the most abundant element and its scale height in the exosphere is the largest (H is the lightest element), hydrogen is certainly the best suited species to be detected in an extra-solar planetary atmosphere. From a detection we will better understand the status of such peculiar planetary atmospheres while a non detection should underline possible important missing links in our present views on such subjects. Reference spectra obtained in quadrature position of the planet will give as a by-product the possible detection of extra-solar planetary Lyman-Alpha aurorae. All collected spectra will also allow to evaluate the interstellar D/H ratio on this line of sight. ================================================================================ Proposal Category: GO Scientific Category: ISM and Circumstellar Matter ID: 9065 Title: Variable Interstellar Absorption toward HD 219188 --- Probing the Structure of an Interstellar Cloud PI: Daniel Welty PI Institution: University of Chicago Within the last 10 years, strong, narrow Na I absorption has appeared at v_SUN ~ -38 km s^-1 toward the halo star HD 219188; that absorption has continued to strengthen, by a factor 2--3, over the past three years. The line of sight appears to be moving into/through a relatively cold, quiescent intermediate velocity (IV) cloud, due to the 13 mas/year proper motion of HD 219188. We propose to monitor the continuing changes in the IV absorption toward HD 219188 over the next three years with STIS echelle spectra --- making use of the rich diagnostics provided by the UV lines of various neutral and singly ionized species to determine abundances/depletions and physical conditions (temperature, density, ionization) as functions of depth within the cloud. In addition to providing a unique view of the detailed structure of an interstellar cloud, these data will yield constraints on grain scattering parameters (from the variation of ionization with depth) and on any dependence of depletion on local density. ================================================================================ Proposal Category: GO Scientific Category: Cosmology ID: 9066 Title: Closing in on the Hydrogen Reionization Edge of the Universe at z<7.2 with deep STIS/CCD Parallels PI: Rogier Windhorst PI Institution: Arizona State Univ., Physics & Astronomy We propose 398 parallel orbits to constrain the Hydrogen reionization edge in emission that marks the transition from a neutral to a fully ionized IGM at a predicted redshifts z~5--10. The edge is due to a rapid change in recombination from the Hydrogen Lyman series at z~ (Baltz Etal 1998), which leaves a sharp signal in the recombination spectrum 3 dex below the Zodiacal background. Z is one of the most important remaining unknown quantities in cosmology. HST is unique in that it can constrain this signal with the STIS CCD plus long-slit, covering Lambda~ 5240 -- 10,270 Angstrom or z=3.3--7.5. In Cycle 8, we took 28 STIS parallel orbits with contemporaneous calibrations to reduce systematics, and set limits to the Hydrogen edge signal of 2* 10^-21 erg cm^2 s Hz sr at z cge 5. This 28 orbit data set has not yet pushed STIS to its absolute calibration limits. We therefore propose parallels in ~260 high and sim100 lower latitude fields (1--3 orbits each) to map any variation in the Zodiacal spectrum across the sky. The combined data will allow us to improve constraints to the Hydrogen reionization edge at 5 z. 7.5 by a factor of 4, within reach of theoretical predictions. We must develop this technique to learn how to optimally develop instruments for NGST to make this measurement with greater sensitivity and at higher redshifts (z=7.5--15). ================================================================================ Proposal Category: SNAP Scientific Category: Quasar Absorption Lines and IGM ID: 9067 Title: UV Detectability of Bright Quasars in the Sloan Fields PI: Wei Zheng PI Institution: The Johns Hopkins University He II LyAlpha absorption at 304(1+z) Angstrom is a far more sensitive tracer of the IGM than its H I counterpart. The recent detection of such absorption in a small handful of quasars, albeit with limited data quality and tiny sample size, demonstrates the great potential of such a probe. Unfortunately, the lines of sight toward the majority of z ~ 3 quasars are intercepted by Lyman-limit systems, and these quasars' UV flux is cut off redward of the He II LyAlpha feature. In order to sample more than just a few clean lines of sight to high redshift, and with good quality spectra, it is necessary to find additional high-redshift, UV-bright quasars. The Sloan Digital Sky Survey, which has discovered more than 2600 quasars and will identify ~20 000 quasars per year, with provides a very substantial resource for new, bright, high- redshift quasars. In a continuation of our SNAPSHOT survey GO-8582, we propose to take MAMA spectra of approximately 30 such quasars in each of the next three cycles. The goal is to find additional rare z > 2.9 quasars having sufficient UV flux to allow detailed He II LyAlpha absorption follow-on spectroscopic studies (at good S/N and resolution) with STIS and COS in future HST cycles. ================================================================================ Proposal Category: GO Scientific Category: Galaxies ID: 9068 Title: Accurate determination of the BH mass in early-type disk galaxies PI: Francesco Bertola PI Institution: Dipartimento di Astronomia, Universita di Padova It is now commonly accepted that almost every galaxy should host in its center a supermassive black hole (BH). Supermassive BH's may have played a major role in galaxy evolution as the recently found correlation between the black-hole mass and the bulge stellar velocity dispersion seems to witness. However it should be kept in mind that the current demography of supermassive BH's suffers of important biases, related to the limited sampling over the different basic properties of their host galaxies. In particular it is evident that the number of BH mass estimates in spiral galaxies is strongly underrepresented. Moreover up to now only two spiral galaxies have very accurate BH mass measurments. Therefore we propose new STIS spectroscopic observations to map the ionized gas velocity field of 3 early-type disk galaxies, for which we will be able to derive high precision BH mass measurements. Indeed the sample galaxies have been selected by means of ground-based high resolution spectroscopy among 37 observed objects, since we recognize in their central regions the clear presence of a circumnuclear Keplerian disk of ionized disk suitable for dynamical modelling. ================================================================================ Proposal Category: GO Scientific Category: AGN/Quasars ID: 9069 Title: Proper Motions in Extragalactic Optical Jets PI: John Biretta PI Institution: Space Telescope Science Institute The flow velocity of extragalactic jets is a crucial missing parameter in our understanding of these objects. We would like to build on our successful HST proper motion measurements in M87, and propose similar measurements in four other optical jets. ================================================================================ Proposal Category: SNAP Scientific Category: Galaxies ID: 9070 Title: A Census of Nuclear Star Clusters in Late-Type Spiral Galaxies: II - Spectroscopy and Stellar Populations PI: Torsten Boeker PI Institution: Space Telescope Science Institute Recent HST observations have revealed that many spiral galaxies have a prominent star cluster in their dynamical center, but statistics for cluster frequency, size, and luminosity remain incomplete. To fill this gap, we are undertaking a Cycle 9 WFPC2 snapshot survey of a well-defined sample of late- type galaxies. However, imaging data alone cannot yield the age distribution of the clusters, which is needed to clarify whether nuclear cluster formation is a one-time event or a recurrent process. This question is important because a central mass concentration is required for some models of bulge formation. In the few cases where cluster ages could be measured from ground-based spectra, they have been found to be rather young ( <=q 10^7.5>yrs) and metal-rich. The question then is whether nuclear clusters indeed form recurrently, or whether ground-based observations are biased towards the brightest and hence youngest clusters. To address this issue, we propose to follow up our Cycle 9 program with a snapshot program of low-resolution STIS spectroscopy of the detected clusters. HST's spatial resolution is required to separate the cluster light from the underlying galaxy emission. We will use stellar population synthesis models to infer the age distribution of the clusters, and to constrain their star formation history. The combined Cycle 9 and 10 programs will provide the first systematic census of nuclear star clusters in any class of spirals. ================================================================================ Proposal Category: GO Scientific Category: Hot Stars ID: 9071 Title: Sakurai's Novalike Object: Real-Time Monitoring of a Stellar Thermal Pulse PI: Howard E. Bond PI Institution: Space Telescope Science Institute This is a continuation of a Cycle 7-9 program. Sakurai's Object (V4334 Sgr) presents a ``once-in-a-lifetime'' opportunity for real-time observations of a star undergoing a final helium thermal pulse. The star rose from obscurity to become an 11th-magnitude ``born-again'' hydrogen-deficient red giant in 1995-96, and currently it is undergoing episodes of atmospheric dust formation. If it follows the pattern that the similar object V605 Aql took early this century, it will soon begin evolving back to high temperature. During the subsequent few years, it will begin to (re)-ionize its large, faint, old planetary nebula as well as the new ejecta, and we should be able to witness the re-establishment and evolution of a fast stellar wind as the effective temperature increases. When the star does begin to heat up, we will initiate Target-of-Opportunity STIS observations to monitor the star's spectroscopic development in the UV at regular intervals, continuing over the next 3 Cycles. We will also use WFPC2 twice over the next 3 years to continue our monitoring of the expansion of the ejecta and to determine the star's proper motion. In combination with ground-based monitoring (optical, IR, and mm), we will thus produce the first detailed case study of a thermal pulse, as the star re-traces its evolution across the HR diagram from the AGB back to the hot planetary-nebula-nucleus phase. ================================================================================ Proposal Category: GO Scientific Category: Hot Stars ID: 9072 Title: Dynamical Masses of White Dwarfs from Resolved Sirius- Like Binaries PI: Howard E. Bond PI Institution: Space Telescope Science Institute In Cycle 8 we initiated a WFPC2 snapshot survey for resolved, ``Sirius-like'' systems containing hot white-dwarf companions of cooler main-sequence stars. Out of 17 systems observed to date, 8 have been resolved with WFPC2 by using UV filters. Two of the resolved systems---56 Persei and ZetaCyg ni---have predicted or known orbital periods short enough that dynamical masses can be determined for the white dwarfs within reasonable times. These would thus add to the extremely small number of white dwarfs presently having accurately and directly measured masses. We propose to image them annually in the UV with WFPC2. In addition, we will observe ZetaCyg with FGS in order to measure the absolute motion of the optical component, needed for the mass solution. We also propose to observe Sirius itself with WFPC2 over the next 3 Cycles. The resulting astrometric data will not only greatly improve the precision of the binary orbit and the dynamical mass measurements for both the main-sequence and white-dwarf components, but will also test definitively for the claimed presence of a third body in this famous system. ================================================================================ Proposal Category: GO Scientific Category: Galaxies ID: 9073 Title: Ultraluminous X-Ray Sources and Intermediate Mass Black Holes PI: Joel Bregman PI Institution: University of Michigan Ultraluminous X-ray sources (ULX) are second only to AGNs in point-source luminosity yet they have no known optical counterparts. These extraordinary X-ray objects, which radiate at the Eddington luminosity of a 30-100 M _dot object, are non-nuclear sources in normal disk galaxies. One explanation is that they are binary systems where the accreting black hole has a mass of 30- 100 M_dot , although this challenges stellar evolutionary models, which do not predict remnants larger than about 10 M _dot . Another possibility is that ULXs are intermediate mass black holes (10^3-10^4 M_dot ), acting as micro-quasars in galaxy disks and representing the link between stellar black holes (4-10 M_dot ) and supermassive black holes (10^6-10^10 M_dot ). We can distinguish between the models by identifying the optical counterparts of ULXs and measuring their colors. This would be a fundamental step in gaining an understanding of these enigmatic and possibly new astronomical objects. ================================================================================ Proposal Category: GO Scientific Category: Galaxies ID: 9074 Title: The Origin and Physics of Gamma-Ray Bursts PI: Andrew Fruchter PI Institution: Space Telescope Science Institute The rapid and accurate localization of gamma-ray bursts (GRBs) promised by the launch of HETE-2 will revolutionize our ability to study these enigmatic but highly luminous objects. We propose a program of HST and Chandra observations to capitalize on this extraordinary opportunity. The association of GRBs to star-forming galaxies now appears strong, in part because of our successful HST-based observing programs. We propose new observations that will provide the most stringent tests yet performed of the hypothesis that GRBs are powered by the collapse of massive stars. We will use STIS CCD spectroscopy to detect broad atomic features of supernovae underlying GRB optical transients, at flux levels more than a factor of three fainter than SN 1998bw. We will use UV, optical, and X-ray spectroscopy to study the local ISM around the GRB, testing whether GRBs preferentially occur in molecular clouds. Our broadband late-time imaging will further test physical models of the relativistic blast wave that produces the bright GRB afterglow, and together with our early spectroscopy will provide unique insight into the relationship between the behavior of the afterglow and the environment of the burster. ================================================================================ Proposal Category: GO Scientific Category: Cosmology ID: 9075 Title: Cosmological Parameters from Type Ia Supernovae at High Redshift PI: Saul Perlmutter PI Institution: Lawrence Berkeley Laboratory In the remaining lifetime of the HST, we have the opportunity to obtain a Hubble diagram of Type Ia supernovae (SNe Ia) that will be of longlasting value as a record of the expansion history of the universe. This record based on SNe Ia used as calibrated standard candles directly constrains the cosmological parameters. Building on our earlier HST work that has yielded increasingly high redshifts and increasingly detailed SN Ia studies, we here propose to measure: one SN Ia at z~0.5, five at z~0.85, and two beyond z~1.0. Of these, one z~0.5 and one z~1.0 SN Ia will be observed spectroscopically with STIS. These data will provide powerful constraints on SN Ia evolution and abnormal dust within or between galaxies, and can reveal all but the most contrived evolutionary effects. Accurate measurement of these high redshift SNe, possible only with the HST, will dramatically shrink the major-axis of the error ellipse in the Omega_M---Lambda plane, decoupling the measurements of Omega_M and Omega_Lambda. This will provide the first check on the CMB measurements of a spatially flat universe, and unambiguously determine whether the universe contains vacuum energy. The Hubble diagram in this redshift range is the only currently feasible way to begin constraining the physics of the ``dark energy'' that is accelerating the universe's expansion. ================================================================================ Proposal Category: GO Scientific Category: Quasar Absorption Lines and IGM ID: 9076 Title: The z = 0.93 DLA in the Gravitationally Lensed QSO HE 0512-3329: a Test of Dust Bias in DLA Samples PI: Max Pettini PI Institution: Institute of Astronomy Gregg et al have recently discovered that the bright QSO HE 0512-3329 is gravitationally lensed into two closely separated images and that the lensing galaxy is in all probability a damped LyAlpha system at z_ abs = 0.9313. Here we request two HST orbits to use STIS to record the profile of the LyAlpha absorption line with sufficient S/N to deduce the column density of H I. This observation will make it possible to measure, for the first time, the abundances of several elements---including Zn, Cr, Fe, Si, and Mn---close (2-3 kpc) to the nucleus of a galaxy at z ~eq 1. There is a suspicion that DLAs at such close impact parameters may be missing from current samples due to dust obscuration, but this obstacle is overcome in this case by the boost provided by gravitational lensing. Establishing whether the metallicity of the galaxy is close to solar, as expected, will provide the first indication of the importance of dust in biasing absorption studies of the universe at z <=q 1. In addition the resolved STIS spectra along the two sight-lines will probe the spatial structure of a DLA on small scales; no such measurement has been performed before. ================================================================================ Proposal Category: SNAP Scientific Category: ISM and Circumstellar Matter ID: 9077 Title: Survey of the LMC Planetary Nebulae PI: Richard Shaw PI Institution: Space Telescope Science Institute A SNAPSHOT survey of all known LMC planetary nebulae (PNe) is proposed to study the co-evolution of the nebulae and their central stars, and to probe the chemical enrichment history of the LMC. We will obtain STIS imaging and medium-resolution slit-less spectroscopy which will yield line fluxes and nebular morphologies in important emission lines, plus magnitudes of the central stars. From these data we will gather a harvest of information: the nebular size, morphology, ionization structure, density, and mass; and the central star temperature, luminosity, and mass. We will test the correlation found in the Galaxy of nebular bipolarity with large progenitor star mass and with chemical enrichment of the outer envelope during the AGB phase. These relationships between PN and central star evolution will be pursued in the LMC with a sample free of distance uncertainties and selection biases. The importance of this program is two-fold: We will determine the late evolutionary paths of the most common stars in a local group galaxy that, in its chemical content, stands in sharp contrast to the SMC, where a complimentary survey is already underway; and we will produce a flux-limited sample of extra-galactic PNe images and spectra that will far exceed in number the galactic PNe already observed with HST, providing an homogeneous database for testing stellar evolution and the chemical history of the LMC. ================================================================================ Proposal Category: GO Scientific Category: Hot Stars ID: 9078 Title: Flares, Magnetic Reconnections and Accretion Disk Viscosity PI: William Welsh PI Institution: San Diego State University Accretion disks are invoked to explain a host of astrophysical phenomena, from protostellar objects to AGN. And yet the mechanism allowing accretion disks to operate are completely unknown. This proposal seeks to observe the ``smoking gun'' signature of magnetically--driven viscosity in accretion disks. Magnetically--induced viscosity is a plausible and generally accepted hypothesis (for esthetic reasons), but it is completely untested. Determining the cause of accretion disk viscosity is of major significance to all accretion--disk powered systems (e.g. CVs, X--ray binaries, AGN and protostellar disks). These data will also firmly establish the importance of magnetic fields in accretion disks. Because of its known flaring properites, we will observe the accretion disk in EM Cyg simulataneously with STIS/FUV and CHANDRA. The simultaneous X-rays are absolutely necessary for the unambiguous detection of accretion disk magnetic reconnection flares. ================================================================================ Proposal Category: AR Scientific Category: AGN/Quasars ID: 9079 Title: AGN outflows: Ionization Equilibrium and Abundances in Seyfert UV absorbers PI: Nahum Arav PI Institution: UC Davis We propose to reanalyze the intrinsic absorption data from nearby Seyfert 1 galaxies, which are indicative of outflows emanating from the AGN. The main goal is to improve our understanding of the ionization equilibrium and abundances (IEA) in these outflows. To do so we will use analysis methods we developed in studying high-z quasar outflows. The quality of the HST high resolution spectroscopic data for Seyferts is very similar (both in S/N and resolution) to the Keck HIRES quasars' data we analyzed in our studies. Furthermore, our quasar outflows have similar widths and are detected in the same lines. We will concentrate on two main projects: a) Extracting more accurate column densities from the detected absorption lines. This step is a prerequisite for any attempt to determine the IEA in the flows. Currently the column densities are uncertain by a factor of a few due to insufficient treatment of partial covering factor effects. b) Extensive photoionization modeling. In addition to relying on better column density determination, we will improve upon the existing photoionization analysis by incorporating inferences from FUSE and X-ray data of these objects, using information from lower resolution HST data as well as upper limits for undetected ions in the high-resolution data and taking into account attenuation of the incident ionizing flux by flow components closer to the source. ================================================================================ Proposal Category: GO Scientific Category: ISM and Circumstellar Matter ID: 9080 Title: Transition from Non-radiative to Radiative Shocks in the Cygnus Loop PI: William P. Blair PI Institution: The Johns Hopkins University We request WFPC2 narrow band HAlpha and O III imaging of faint filaments in the northeastern Cygnus Loop that represent the location of the primary shock front as it first encounters the ISM. The primary character of these filaments is non-radiative, but certain filaments are poised at the onset of becoming radiative, providing a unique laboratory for testing shock model predictions of the development and evolution of astrophysical shock waves. We also request a STIS/MAMA far-UV spectrum cutting across one of the transition filaments that has a clean geometry (selected from the requested imagery) to study the physical scale over which the strong far-UV resonance lines of N V, C IV and He II ramp up in the post-shock flow. Reobservation of a set of HAlpha filaments first observed with HST/WFPC2 in 1997 will permit an accurate proper motion measurement which, in conjunction with existing ground-based measurements, will permit us to assess directly whether the filament has decelerated over the last 50 years. ================================================================================ Proposal Category: GO Scientific Category: Star Formation ID: 9081 Title: Accretion in the planet-forming disks of the TW Hya association PI: Nuria Calvet PI Institution: Smithsonian Astrophysical Observatory We propose to obtain STIS/MAMA high signal-to-noise, low resolution ultraviolet spectra of the only two stars in the ~ 10 Myr old TW Hya association that are still accreting to measure the mass accretion rate through their disks. With these measurements we will be able to assess the gas content in these disks which show clear signs that dust is rapidly evolving towards planetesimals and planets, and obtain crucial parameters to address the problems of planet migration and survival at 10 Myr, the time-scale for planet formation according to meteoritic and preliminary astronomical evidence. ================================================================================ Proposal Category: GO Scientific Category: ISM and Circumstellar Matter ID: 9082 Title: Expansion distances to the symbiotic Miras He 2-104 and He 2-147 PI: Romano Corradi PI Institution: Isaac Newton Group of Telescopes We propose to measure the expansion parallax of the nebulae around the binary symbiotic Miras He 2-104 (the Southern Crab) and He 2-147 by means of high resolution WFPC2/F658N images to be taken at two different epochs. Given the large outward velocities of these nebulae inferred from ground-based spectroscopy, their apparent expansion can be measured by HST imaging over timescales of only 2-3 years. For He 2-104 we have already obtained ``Epoch 1'' HST images (cf. STScI-PRC-PR99-32). Combining the angular and radial velocity expansions will straightforwardly yield the distance to the proposed targets. Knowledge of the distance to these nebulae will provide a solid contribution to a variety of research fields such as (a) the energetics of nuclear burning in symbiotic binaries containing a Mira, (b) the pulsation mode of binary Miras, and (c) the viability of Mira symbiotics as supersoft X- ray sources and potential progenitors of Type Ia supernovae. HST high resolution imaging of the nebulae combined with ground-based spectroscopy will also address the still debated issue of the formation of bipolar nebulae by collimated outflows from evolved stars. ================================================================================ Proposal Category: GO Scientific Category: Hot Stars ID: 9083 Title: Critical spectroscopic variations in Eta Carinae PI: Kris Davidson PI Institution: University of Minnesota The very massive, unstable, persistently enigmatic star Eta Carinae has implications for several branches of astrophysics. Despite a series of remarkable discoveries in previous HST data, the nature of the central object remains elusive. Fortunately, recent developments offer, for the first time, an approach that can settle a number of long-standing questions which have been obstacles to understanding this unique object. A 5.5-year spectroscopic and X-ray cycle is now well established. STIS provides the most promising and very likely the only way to test whether Eta Car is a 5.5-year binary system. If it is, STIS gives by far the best constraints on the companion star, orbit, etc., needed to assess mechanisms for past outbursts and ejecta. If binary models don't work, then the 5.5-yr effect is probably a thermal cycle which gives novel information about the star's structure. In addition to the periodicity, the unprecedented brightening found with STIS in 1999 has continued at a diminished rate and merits followup observations. We sense that these recently discovered effects offer a likely breakthrough if Eta Car can be observed repeatedly with STIS through the current 5.5-year period, 1998.0--2003.5. During HST Cycle 10 the pace is expected to increase as this object enters the phase preceding its next major ``event.'' ================================================================================ Proposal Category: GO Scientific Category: Hot Stars ID: 9084 Title: Physical Parameters of the Erupting Luminous Blue Variable NGC 2363-V1 PI: Laurent Drissen PI Institution: Universite Laval In 1996, we reported the discovery of a bright variable star in the giant extragalactic H , ii region NGC 2363. Subsequent photometry and high quality HST/STIS spectroscopy of this star, NGC 2363-V1, revealed that we are witnessing a significant event in the evolution of a massive star, namely a major eruption of a Luminous Blue Variable (LBV). A quantitative analysis of the STIS datasets gathered in 1997 and 1999 allowed us to determine the luminosity, mass loss rate, wind terminal velocity, surface temperature and even Fe content of this erupting LBV. Because such events are rare, continuous monitoring of the physical parameters of NGC 2363-V1 over the course of its present eruption will provide an invaluable set of constraints for theoretical models. We therefore propose to obtain high quality STIS spectra of this star once a year for the next three observing Cycles. ================================================================================ Proposal Category: GO Scientific Category: AGN/Quasars ID: 9085 Title: Measuring the masses of high-z quasar host galaxies PI: James Dunlop PI Institution: University of Edinburgh In recent years HST has played a major role in establishing the close link between black-hole mass and spheroid mass in both quiescent and active galaxies in the local universe. Consequently black-hole and spheroid formation/growth are now viewed as intimately related processes, and establishing the mass of quasar host galaxies as a function of redshift is now seen as a key measurement in observational cosmology ( eg Kauffmann & Haehnelt 2000). From our Cycle 7 NICMOS program we have derived the best estimate to date of the mass evolution of the hosts of both radio-quiet and radio-loud quasars out to z ~eq 2. Under the assumption of passive stellar-population evolution our results are consistent with the black-hole/spheroid population being unchanged out to z ~eq 2. However, the crucial assumption of passive evolution needs to be tested, because discovery of any substantial star- formation activity would yield a reduction in luminosity-estimated host masses at z ~eq 1 - 2, potentially bringing our results into line with the order-of- magnitude mass reduction predicted by the hierarchical models of Kauffmann & Haenhelt (2000). We thus propose WFPC2 imaging of our luminosity-matched quasar sub-samples at z ~eq 1 and z ~eq 2 which, when coupled with our NICMOS data, will yield the first reliable rest-frame U-V colours for high-z quasar hosts, and hence the first unbiased measurement of host-galaxy masses out to z ~eq 2. ================================================================================ Proposal Category: GO Scientific Category: Galaxies ID: 9086 Title: Investigating the Formation History of Spiral Galaxy Halos PI: Henry Ferguson PI Institution: Space Telescope Science Institute We propose to constrain the origin of spiral galaxy halos by studying stellar populations near the tip of the red giant branch. This will be the first systematic study of this population in external galaxies and will quadruple the sample of normal spiral galaxies for which the halo metallicity distribution function is measured. This larger sample will permit us to study the relationship between the bulge, disk, and halo components and between halos and globular systems. Such correlations will in turn provide indications as to whether the halo, bulge, and globular cluster systems built up nearly simultaneously in the early universe or were accreted over time through different kinds of merging events. ================================================================================ Proposal Category: GO Scientific Category: Galaxies ID: 9087 Title: Black Hole X-ray Transients and X-ray Binaries in M31 PI: Michael Garcia PI Institution: Smithsonian Astrophysical Observatory As part of the Chandra Guaranteed Time Observations (GTO) program, we are searching M31 for x-ray transients. A complimentary GO program to study supersoft x-ray sources in M31 has recently been approved, and it will significantly expand our ability to find x-ray transients in M31. The x-ray properties of these transient sources (spectra, variability) allow us to determine whether the accreting object is a black hole or a neutron star. We propose HST observations of these x-ray transients to determine the nature of the mass-losing star. Massive stars will show little (<2 mag) change in their UV luminosities during outbursts, while low-mass stars will show large (>5 mag) changes in their UV luminosities. By determining the nature of the primary (accreting) and secondary stars in these x-ray transients, we will have the first dataset that will allow the evolution of black hole and neutron star binaries to be studied in an external galaxy. As >70 transients in the Milky Way (MW) contain black hole primaries, we expect that a major result will be an understanding of the formation of stellar mass black holes in another galaxy. Recent HST/DD observations of one M31 x-ray transient demonstrate that these observations are entirely feasible. ================================================================================ Proposal Category: SNAP Scientific Category: Galaxies ID: 9088 Title: A Next Generation Spectral Library of Stars PI: Michael Gregg PI Institution: University of California, Davis We propose to use the low dispersion UV and optical gratings of STIS to produce a ``Next Generation'' Spectral Library of 600 stars for use in modeling the integrated light of galaxies and clusters. The library will be roughly equally divided among four metallicities, very low (Fe/H < -1.5), low (-1.5 < Fe/H < -0.5), near-solar (-0.5 < Fe/H < 0.1), and super-solar (Fe/H > 0.1), well-sampling the entire HR-diagram in each bin. Such a library will surpass all extant compilations and have lasting archival value, well into the Next Generation Space Telescope era. Because of the universal utility and community-broad nature of this venture, we waive the entire proprietary period. ================================================================================ Proposal Category: GO Scientific Category: Cool Stars ID: 9089 Title: FGS Parallaxes of Cataclysmic Variables: Understanding Their Peculiar Secondary Stars PI: Thomas Harrison PI Institution: New Mexico State University We have recently completed an HST FGS program that measured high-precision (+/- 0.5 mas) parallaxes for three dwarf novae. The true distances for all three objects turned out to be substantially larger than predicted. The results for SS Cyg alone, will challenge existing models to explain its large accretion luminosity. As part of that program we obtained infrared spectra to examine the spectral types of the secondary stars. The combination of the parallaxes, the spectra, and existing optical/IR photometry has revealed that the secondary stars of cataclysmic variables (CVs) are peculiar, and are clearly affected by close-binary star evolution. We propose a program to measure precise parallaxes for three additional CVs (WZ Sge, RU Peg, and YZ Cnc), whose orbital periods span a much larger range than explored in our previous program. This will allow us to examine how the accretion luminosity and secondary star change with orbital period. To do this will require 18 total HST orbits over two separate cycles. Twelve orbits in Cycle 10 (four per object), and six orbits in Cycle 11 (two per object). Only the FGS on HST is capable of providing timely, high-precision parallaxes on CVs of particular astrophysical interest. ================================================================================ Proposal Category: GO Scientific Category: Cool Stars ID: 9090 Title: Transition Region Emission in Very Low Mass Stars PI: Suzanne Hawley PI Institution: University of Washington The origin of the magnetic heating which produces hot outer atmospheres in late-type stars is one of the most interesting, and elusive, problems in stellar astrophysics. Our poor understanding is due in part to the lack of data for a large and varied sample of stars, which are needed to provide the basis for a general theory. Observationally, our knowledge is particularly sparse for the very low mass stars. In fact, diametrically opposed conclusions have been reached in this field: the available data has been interpreted 1.) to indicate that magnetic heating of the hot transition region and corona becomes relatively more important in stars of later spectral type (lower mass) - the pre-1999 position; and 2.) to claim that the magnetic heating is insufficient to produce these regions at all, except during flares, in very low mass objects - the current widely held view. The manifestations of magnetic activity at the stellar/brown dwarf boundary have yet to be probed in transition region diagnostics; previous IUE and HST/GHRS observations were not sensitive enough to provide constraining data. Our proposed HST/STIS observations of three very low mass stars will conclusively show if quiescent magnetic heating sufficient to produce a hot outer atmosphere still exists in these objects, or whether they are categorically different than higher mass M dwarfs. ================================================================================ Proposal Category: GO Scientific Category: Star Formation ID: 9091 Title: Evolution of Star Forming Environments in H II Regions PI: Jeff Hester PI Institution: Arizona State University There are significant difficulties with the current understanding of the YSO disks and evaporative envelopes in the Orion nebula and how these objects fit into the broader picture of star formation. These are generally imagined to be a long-lived population, yet searches have turned up few such objects anywhere but Orion. Further, the observed masses of the disks in Orion combined with their observed evaporative mass loss rates imply ages for the objects of only a few * 10^4 years. Henney and O'Dell (1999) claim that no solution is possible unless submillimeter determinations of disk masses are off by a factor of 30. We suggest instead that these objects are only 10^4 years old, and that we are catching them as they are being uncovered by the advancing ionization front located only about 2 * 10^17 cm behind the Trapezium. When a YSO is uncovered by an advancing ionization front it will pass through two short-lived stages, first as an evaporating gaseous globule (EGG) such as those seen in M 16, then as an evaporating disk such as those seen in Orion. Such objects will live for only a few * 10^4 years, and should be found only in close proximity to molecular cloud walls. We propose to test this idea by looking for EGGs and silhouette disks in two young clusters and along one molecular cloud wall. ================================================================================ Proposal Category: GO Scientific Category: ISM and Circumstellar Matter ID: 9092 Title: V605 Aql: Sakurai's older brother PI: Kenneth Hinkle PI Institution: NOAO Post-AGB stars can undergo a final episode of helium shell burning after the star has ejected a planetary nebula and has started on the white dwarf track. Starting in 1996 Sakurai's star has been observed to undergo a final helium shell flash. The same series of events occurred in V605 Aql 91 years ago. These stars both ejected a shell of gas first seen as a pseudo-photosphere and then as a thick dust envelope. The shells are expanding at sim100 km s^-1 and in the case of V605 Aql the shell now appears about 1" across. We propose to image this shell with WFPC2. The shell contains ionized material as well as dust. By combining WFPC2 and Gemini high spatial resolution infrared images we will discriminate between bipolar and lumpy models of the circumstellar shell. Since the precursor to the final flash was a white dwarf, as opposed to an AGB star with a complex structure and complex circumstellar environment, the observations will provide a test of the origins of structure in circumstellar shells and planetary nebulae. Comparison with a decade old FOC image may yield the luminosity of V605 Aql. ================================================================================ Proposal Category: GO Scientific Category: Star Formation ID: 9093 Title: Resolving Molecular Hydrogen Disks Around T Tauri Stars PI: Christopher Johns--Krull PI Institution: University of California Molecular hydrogen is believed to be the dominant constituent of circumstellar disks at radii ~ 0.1 - 5 AU around young stars. Fluoresced UV lines pumped by Ly-Alpha are bright and offer a valuable probe of H_2 in disks around young stars, with the ultimate goal being the ability to study the structure and evolution of the planet forming regions around these stars. The limited H_2 data now available for T Tauri stars (TTS) are inadequate to isolate the location of molecular hydrogen emission, though the current data suggests emission from ~ 2 AU in the disk around DF Tau. We will use deep, high resolution (E140H) STIS-FUV spectra to resolve the distinctive spectral line signature of Keplerian rotation in disks around two nearly edge on TTS. These will be the first high resolution UV spectra of any TTS and will provide the radius in the disk at which molecular hydrogen can survive. This in turn indicates the inner boundary of the ``dead zone" in TTS accretion disks which is the likely location for the formation of planets. ================================================================================ Proposal Category: GO Scientific Category: Hot Stars ID: 9094 Title: The Wind-Wind Interactions in HD 5980 PI: Gloria Koenigsberger PI Institution: UNAM-Instituto de Astronomia HD 5980 is the visually brightest object in the SMC. It contains a close eclipsing binary LBV+WR (=Star A+Star B), the only one known to exist, with the possible exception of Eta Carinae. The LBV underwent a great eruption in 1994, ejecting <10^-3 M_dot at velocities in the range of 200-800 km s^-1. After the eruption, its wind velocity has been steadily increasing, and producing a circumstellar (CSM) fast-wind/slow-wind interaction region, which has now become visible spectroscopically in the C IV and Si IV lines at an expansion velocity of -680 km s^-1. These narrow features varied over a 1 year timescale. It is likely that HD 5980 is forming an H II region analogous to the Homunculus in Eta Carinae. In addition, the wind-wind collision shocked region between the two stars currently (1999-2000) forms a shock cone that winds tightly around the WR star. The purpose of this proposal is to: a) Determine the LBV's wind velocity close to the time when it will be observed with XMM and CHANDRA; b) follow the changes in the high velocity CSM absorption features; and c) Constrain the radial velocity variability of the third component, Star C, in order to determine whether it is bound to the A+B pair. The three objectives can be achieved with just two visits, using STIS to obtain the FUV+NUV spectrum. HST is the only observatory capable of providing these data. A reduced 3 month proprietary period is proposed. ================================================================================ Proposal Category: GO Scientific Category: AGN/Quasars ID: 9095 Title: Simultaneous HST, Chandra and FUSE Observations of Intrinsic Absorbers in AGN PI: Gerard Kriss PI Institution: Space Telescope Science Institute Photoionized, warm absorbing gas is an important component of the nuclear structure of AGN. Approximately half of all low-z AGN show high-ionization UV absorption lines and X-ray warm absorbers, but the relationship of the UV- absorbing gas to the even higher ionization X-ray absorbing material is not yet understood. Only a handful of high-spectral-resolution observations with HST, Chandra or FUSE currently exist (NGC 4151, NGC 3516, NGC 3783, NGC 5548, Mrk 509). These show a diversity of kinematic structure and ionization states in the absorbers. We propose to increase significantly the sample of low-redshift AGN studied at high spectral resolution in the UV and the X-ray by obtaining simultaneous HST, Chandra, and FUSE spectra of NGC 7469 and Mrk 279. Both are bright AGN with O vi absorption resolved in recent FUSE observations. The new simultaneous observations will resolve the kinematics and ionization state of both the UV and X-ray absorbers. This will permit a definitive assessment of their relationship and give clues to their location in the nuclear region. Using the variety of ionization states and the multiple absorbing components, we will also reconstruct the ionizing spectrum. Understanding the absorbing gas and its influence on the radiation escaping from AGN has important implications for the radiative input to the IGM and the origins of the X-ray background. ================================================================================ Proposal Category: GO Scientific Category: Stellar Populations ID: 9096 Title: Objective-Prism Spectroscopy of Massive Young Clusters PI: Jesus Maiz-Apellaniz PI Institution: Space Telescope Science Institute Most of the present knowledge of the UV spectral properties of massive young clusters (MYCs) is based on IUE data with marginal spatial resolution. We propose to greatly improve the spatial information by obtaining STIS NUV-MAMA objective-prism spectroscopy in the 1300-3600 Angstrom range of three nearby extragalactic regions with a total of ~ 10 MYCs. Slitless techniques are seldom attempted on crowded clusters due to the overlap among different sources. We plan to overcome that problem by observing with two different roll angles, using comparison UV and optical images from the HST archive, and developing automatic extraction techniques based on codes already written by some of the authors. Some of the issues that will be tackled include: (i) Is there an age difference between the core and the outer parts of the clusters? (ii) What is the importance of differential extinction in the estimation of the cluster age? (iii) Is the absence of the 2175 Angstrom bump in starbursts due to geometrical effects or is it an intrinsic property of the dust? (iv) Are the properties of the dust homogeneous or do they vary with position? The STIS NUV prism is ideal for this type of study since it provides relatively higher spectral resolution for the features around 1500 Angstrom and lower resolution at longer wavelengths, where the sources are generally less intense and the background is higher. ================================================================================ Proposal Category: GO Scientific Category: Hot Stars ID: 9097 Title: The Mass-Luminosity Relationship for High Mass Stars: Resolving the `Mass Discrepancy' with HST PI: Philip Massey PI Institution: Lowell Observatory The mass-luminosity relation is well determined for intermediate-mass stars, and on-going HST observations are extending the relationship to stars of very low mass. Here we propose to obtain similar, fundamental data on the highest mass stars, where physical complications (mass-loss, mixing) make such studies a necessary check on the stellar models. Empirical checks are particularly important given the factor-of-two ``mass discrepancy" that exists in the masses inferred from stellar atmospheres, and those computed from stellar interiors. We have selected 7 nearby, early-type stars with established velocity variations characteristic of long-period binaries. We will attempt to resolve these systems using the FGS. The separations, combined with double- lined spectroscopic orbit solutions, will provide unambiguous mass determinations. Success for even one system will allow us to anchor the high- luminosity end of the mass-luminosity relationship, and resolve the mass discrepancy. ================================================================================ Proposal Category: GO Scientific Category: Hot Stars ID: 9098 Title: The Spectrum and the Light Curve of the Nearest Millisecond Pulsar PI: George Pavlov PI Institution: Pennsylvania State University PSR J0437--4715 is the nearest and the brightest millisecond (recycled) pulsar, and the only one that has been well studied at X-ray/EUV energies, where it has a strong pulsed signal. It is the most promising candidate for detecting the first optical counterpart of a millisecond pulsar. The HST has the unique ability to detect the cyclotron spectral line in the far UV from this weakly magnetized neutron star and to measure directly, for the first time, the magnetic field of a rotation-powered pulsar. The cyclotron line would be recognized by its sharp pulse profile in the FUV MAMA detector. The spectral and timing analysis of the far-UV continuum will allow us to study synchrotron radiation from the pulsar magnetosphere and thermal radiation from the surface of the neutron star. The magnetospheric and thermal components will be distinguished by their different pulse shapes and spectral slopes. ================================================================================ Proposal Category: GO Scientific Category: Galaxies ID: 9099 Title: High Spatial Resolution Spectroscopy of the Massive Globular Cluster G1 PI: R. Michael Rich PI Institution: University of California at Los Angeles We propose to obtain high spatial resolution, long-slit spectroscopy of the most luminous globular cluster in the Local Group, G1 in M31. The kinematic structure obtained with these data will provide a stringent test of whether a central black hole exists, thereby determining whether globular clusters share the same intimate connection that normal galaxies do with their black holes. The central surface brightness of the core of this cluster reaches 13.5 V mag arcsec^-2, and the core radius of the cluster is 0.9 pc; both these properties allow for detailed kinematic information using HST. If a black hole is present, and G1 falls on the black-hole mass/sigma correlation recently established for bulges and ellipticals, the mass should be 6*10^4M_dot, and the velocity dispersion should rise to 36 km s^-1. Detection of a black hole in G1 would extend the black-hole mass/sigma relationship to masses 100 times lower than the lowest mass nuclear black hole currently known, and establish a solid connection between the formation of galaxies and globular clusters. The data will also provide the basis for an excellent dynamical model of G1 and a study of stellar population gradients in this unique cluster. Parallel imaging with WFPC2 will produce a very deep color-magnitude diagram of the M31 halo field stars adjacent to G1. Short exposures of the M31 halo hints at a possible intermediate-age population, which may be revealed in deeper parallels. ================================================================================ Proposal Category: GO Scientific Category: Cool Stars ID: 9100 Title: High-Velocity Collimated Outflows and Equatorial Toroids in Cool Stars: A Study of V Hydrae and PI^1 Gru PI: Raghvendra Sahai PI Institution: Jet Propulsion Laboratory, Caltech The two cool red giant stars V Hya and PI^1 Gru show strong observational evidence for the presence of high-velocity collimated outflows and equatorial toroids, both of which have been postulated to play significant roles in the formation of bipolar planetary nebulae. However the limited resolution of existing ground-based observations makes it impossible to unambiguously identify structures which reveal the mechanism of jet formation or elucidate the cause of bipolarity. We propose HST imaging and long-slit spectroscopic observations of the circumstellar environment of V Hya and PI^1 Gru. These observations will provide the first high-resolution images at any wavelength of these key objects. We will thus obtain an unprecedentedly high-resolution glimpse of AGB stars transitioning into preplanetary nebulae, allowing us to probe the structure and kinematics of their very fast outflows and the relationship of those outflows to the structures seen in molecular line emission. Our HST study of these transition objects should elucidate the nature and history of the mass-loss processes which terminate the AGB evolution of intermediate-mass stars and begin their transition into the proto-planetary and planetary nebula phases. ================================================================================ Proposal Category: SNAP Scientific Category: ISM and Circumstellar Matter ID: 9101 Title: Toward Understanding the Bipolar Geometries of Preplanetary Nebulae with High-Velocity Polar Flows PI: Raghvendra Sahai PI Institution: Jet Propulsion Laboratory, California Institute of Technology Most planetary nebulae (PNs) show bipolar morphology, in striking contrast to the largely round shapes of the circumstellar envelopes of the AGB stars from which they evolve. Several lines of evidence, including high spatial- resolution imaging with HST, suggest that high-velocity collimated outflows occuring during the transition from AGB to the PN phase -- the preplanetary nebula (PPN) phase -- are significant agents for imposing bipolarity on the circumstellar environment. Unfortunately, kinematic data at a comparable spatial resolution has been lacking, limiting our understanding of the physical mechanisms responsible for the bipolarity. We have therefore begun a multiwavelength program, including interferometric spectral-line imaging in the radio and HST imaging, to study PPNs in detail. We find, for two bipolar PPN, that the spatio-kinematic distribution of the OH masers relative to the HST optical structure is consistent with the hypothesis that the optical lobes result from a fast outflow interacting with the slow, dense AGB wind, producing an increasing radial velocity from the equator to the poles. We propose imaging of 17 PPNs with WFPC2 for comparison with high-resolution spectral-line images (being obtained with VLA/MERLIN/ATCA), enabling us to test this hypothesis, and to understand the fast outflow and how its hydrodynamical interaction with the AGB wind produces a bipolar nebula. ================================================================================ Proposal Category: GO Scientific Category: ISM and Circumstellar Matter ID: 9102 Title: A YSO-like pulsed astrophysical jet and bipolar nebula in a dying star: WFPC2/STIS study of He2-90 PI: Raghvendra Sahai PI Institution: Jet Propulsion Laboratory We have discovered an extended, highly-collimated, bipolar jet in He2-90, an object long classified as a planetary nebula (PN). The discovery images (obtained with WFPC2/HST) show that the morphology of He2-90 does not look like that of any known PN, but resembles that of a classical young stellar object (YSO). This appears to be a unique object. We will determine the speed of the jet (only slightly inclined to the sky plane) through proper motion observations of the knots in the jet: a 2nd-epoch WFPC2 H-alphapha image will be obtained for comparison with the Sep99 discovery image. It is crucial to observe the velocity field of the flow at the highest spatial-resolution, as close as possible to the origin of the jet in order to constrain theories for how the jet is driven, and the nature of the central object. We propose to do this by mapping the jet near the central source using the long-slit, medium resolution mode of STIS. We also propose supplemental observations: low resolution STIS spectra for obtaining nebular diagnostics, coupled with narrow-band imaging with WFPC2 in emission lines such as NII, OI and OIII and continuum filters for mapping excitation variations in the nebula and jet and the extinction in the central dense dusty disk region. Coordinated Chandra X- ray observations (with ACIS-I) will be made to check the association of an EGRET >~mma-ray source which lies in the direction of He2-90. ================================================================================ Proposal Category: GO Scientific Category: Star Formation ID: 9103 Title: Resolving New Examples of, Edge-on Young Stellar Object Disks PI: Karl Stapelfeldt PI Institution: Jet Propulsion Laboratory Edge-on, optically thick circumstellar disks have been imaged by the Hubble Space Telescope in association with several nearby young stars. In these systems, the central star is occulted from direct view, large PSF artifacts are absent, and the disk reflected light is clearly seen. It is for these objects in nearby star-forming regions that HST has provided the best, highest resolution (7-10 AU) views to date of disks which may form planetary systems like our own. Comparison of edge-on disk images with scattered light models has allowed key structural parameters such as the disk outer radius, vertical scale height, radial density profile, total mass, and dust grain properties to be determined. To reveal the diversity of protoplanetary environments, it would be very valuable to identify and study additional examples of edge-on disks. The edge-on disks detected thus far share a signature characteristic: they are unusually faint in the near-infrared yet still optically visible. In a review of the literature, we have uncovered an additional eight optically visible young stars associated with nearby molecular clouds whose faintness in the near-IR suggests that they are edge-on disks seen entirely by scattered light. Three are sources of Herbig-Haro jets. We propose R and I band imaging of these eight objects, the faintest nearby T Tauri stars. ================================================================================ Proposal Category: GO Scientific Category: Star Formation ID: 9104 Title: A WFPC2 Study of Proplyds and a Protostellar Condensation at the Center of M20 PI: Farhad Yusef-Zadeh PI Institution: Northwestern University The Trifid nebula (M20) is a well-known prominent optical HII region trisected by bands of obscuring dust lanes and excited by an O7.5 star HD 164492A. Our recent study of near-IR ground-based observations of this region at J, H, K and L show all seven components of HD 164492 (A to G) identified optically. Our sub-arcsecond radio continuum VLA and ground-based observations of M20 also show free-free emission from three stellar sources (B, C and D) and a bright rim outlining a protostellar condensation (TC1) lying close to the O7V star (HD 164492A) at the center of the nebula. Based on a number of strong arguments, these stars have disks associated with them and their envelopes are photoionized externally by the UV radiation from the hot central star, HD 164492A. The proposed WFPC2 observations are intended to search for neutral protoplanetary disks ``proplyds'', to study the optically bright rim of ionized gas associated with TC1 for signs of star formation, and to make a detailed subarcsecond determination of extinction toward the dust lanes of M20 using HAlpha and 6cm data. ================================================================================ Proposal Category: GO Scientific Category: Cool Stars ID: 9105 Title: Determination of the Distances and Masses of 3 Galactic Cepheids PI: Derck Massa PI Institution: Raytheon ITSS We propose to continue a successful observing strategy which enabled us to accurately measure angular separations < 10^-2 with the FOC for binaries with Cepheid primaries and main sequence B or A star secondaries (our accuracy should improve to ~ 10^-3 with STIS). Once measurements are available at two carefully selected phases and these are combined with spectroscopic orbits, the angular information will enable the masses and distances for the binaries to be determined from Newton's laws and Euclidean geometry. The distances determinations amount to bypassing two rungs of the cosmic distance ladder: the moving-cluster distance to the Hyades and main sequence fitting of clusters containing Cepheids. The mass determinations will provide the first direct dynamical mass measurements for Cepheids, providing sorely needed quantitative information on this poorly understood stage of massive star evolution. ================================================================================ Proposal Category: GO Scientific Category: Galaxies ID: 9106 Title: The Biggest Black Holes PI: Douglas Richstone PI Institution: University of Michigan Searches for supermassive black holes in galaxy centers have led to the discoveries that (1) most or all hot galaxies contain massive dark objects at their centers, presumably black holes; (2) there is a tight correlation between the black-hole mass and the luminosity-weighted velocity dispersion of the hot component of the galaxy. This remarkable relationship suggests a strong link between black-hole formation, AGN activity, and galaxy formation, and once it is understood this link should advance our understanding of all three processes. Guided by the mbh-Sigma relation, we will search for the most massive black holes in galaxies within ~100 Mpc. Our results should (1) explore the nature of the mbh-Sigma relation for the most luminous galaxies and the most massive black holes; (2) identify the local remnants of the brightest quasars, which should have larger black-hole masses than any yet detected; (3) test whether black-hole masses depend on the nature of the central region of the host galaxy (core or power-law). High-mass black holes are difficult to detect, and thus have traditionally been under-represented in HST surveys; however, in the past decade our group has used HST photometry and spectroscopy to investigate the central regions of over 15 galaxies, and we have well-honed observational and theoretical tools for this task. ================================================================================ Proposal Category: GO Scientific Category: Galaxies ID: 9107 Title: The Fundamental Plane for Nuclear Black Holes PI: Douglas Richstone PI Institution: University of Michigan Searches for supermassive black holes in galaxy centers, conducted with HST and other telescopes, have led to the discoveries that (1) most or all hot galaxies contain massive dark objects at their centers, presumably black holes; (2) there is a remarkably tight correlation between the black-hole mass and the luminosity-weighted velocity dispersion of the hot component of the galaxy. This mbh-Sigma relation has a scatter which is <0.3 dex in mbh and consistent with zero. This relationship suggests a strong link between black- hole formation, AGN activity, and galaxy formation, and once it is understood this link should advance our understanding of all three processes. The goal of this proposal is to investigate the scatter in the mbh-Sigma relation and the role of possible second parameters, by examining a sample of galaxies at fixed velocity dispersion Sigma=200+/- 20 kms. This approach decouples the effects of a second parameter from uncertainties in the shape of the mbh-Sigma relation, and minimizes spurious correlations because all of the galaxies will be studied using the same well-tested observational and modeling techniques. The sample is chosen to explore second parameters such as environment, X-ray properties, Hubble type, luminosity profile, etc. This work thus treads a path similar to the one that took us from simple bivariate relationships among galaxy properties to the deeper concept of a fundamental plane of galaxies. ================================================================================ Proposal Category: GO Scientific Category: Hot Stars ID: 9108 Title: Observing the Next Nearby Supernova PI: John Bahcall PI Institution: Institute for Advanced Study If a neutrino-producing supernova (SN) explodes in the Galaxy, the Large or Small Magellanic Clouds, or a close member of the Local Group, it will be detected first by operating neutrino experiments: Super-Kamiokande, SNO, MACRO, and AMANDA. The supernova neutrino early warning system will notify photon observers throughout the world within an hour of the neutrino detection. Although the per-year probability of observing a neutrino SN (within 100 kpc) is small, the detection would be importantly scientifically and of widespread interest. The optical counterpart could be much brighter than normal extragalactic SNe. A bright nearby supernova detected by other means would also be of great interest and should activate this proposal. We propose unique STIS ultraviolet spectroscopic observations to measure the principal metallic lines, and hence the composition, velocity, and physical state, of the outermost atmosphere of the exploded star. In addition, we propose narrow- and broad-band imaging to provide information about the stellar environment and early morphology unobtainable from the ground. The data, especially images, will be valuable for public outreach and will be released immediately by NASA. ================================================================================ Proposal Category: GO Scientific Category: Cool Stars ID: 9109 Title: Mapping the Chromosphere of the K Supergiant in the Eclipsing Binary 31 Cygni PI: Philip Bennett PI Institution: University of Colorado Red supergiants (RSGs) are responsible for returning the greatest contribution of mass to the ISM, but this mass loss process, can not be modeled in a fundamental way because the physical mechanism responsible remains uncertain. This difficulty has profound implications for stellar population sythesis and galactic evolution. We propose to address this problem by observing the chromosphere and wind of the supergiant primary in the long-period (10.36 yr) eclipsing binary 31 Cygni. This binary has the largest orbital separation relative to primary size (and the least interaction) of the known Zeta Aur binaries. The next eclipse in 2003 will be the last available during the lifetime of HST; if this project is to be done at all, it must be started now ================================================================================ Proposal Category: GO Scientific Category: Solar System ID: 9110 Title: A Search for Kuiper Belt Object Satellites PI: Michael Brown PI Institution: Caltech The large number of collisions thought to have taken place in the primordial Kuiper belt suggests that many Kuiper belt objects (KBOs) could have suffered binary-forming collisions similar to that which formed the Pluto -- Charon binary. Detection of such KBO satellites would allow us to measure KBO masses, would help us to understand the past collisional environment of the Kuiper belt, and would give a context to the otherwise unique-seeming formation of the Pluto -- Charon binary. We propose a STIS CCD search for satellites around a large sample of KBOs for which we can obtain sufficient signal-to-noise and angular separation to robustly detect Charon-analog satellites. The time is right to invest in such a large survey: our preliminary HST search for satellites is just completing and has demonstrated a highly successful observing strategy; the number of bright KBOs has now increased to the point where a statistically meaningful sample can be observed; and many studies of KBO properties and history will benefit greatly from having a concrete knowledge of KBO masses. We are performing complementary deep searches around each of these KBOs with Keck, but only HST resolution will allow us to probe the inner ~0.5 arcseconds where we expect collisionally formed satellites analogous to Charon to appear. We have carefully constructed a program optimized to detect any such very close satellites. ================================================================================ Proposal Category: GO Scientific Category: Hot Stars ID: 9111 Title: The UV Light Echo of Shock Breakout During SN 1987A PI: Arlin Crotts PI Institution: Columbia University Light echoes (transient reflection nebulae) from SN1987A were discovered in the optical in 1988 and have been detected in the vacuum ultraviolet by IUE. The UV data would be the first ``direct'' observation of the hot spectrum emitted by a supernova shock destroying its progenitor star; unfortunately the large aperture and pointing instabilities of IUE make these data difficult to calibrate and interpret in great detail. The breakout signal has also been modified by the spectral reflectance of the echoing dust. We propose to confirm the UV detection and to disentangle the incident SN spectrum from the dust reflectance by observing the UV echo at two scattering phase angles and combining them with HST and ground-based data. Sampling two echoes at widely- spaced spectral points and two scattering angles will provide us with enough independent information to factor these separately. The resulting early UV spectrum of SN 1987A will allow a direct test of theoretical models of supernova shock propagation and breakout from a star, as well as provide an accurate input ionization spectrum for understanding the excitation and recombination of gas in the observed circumstellar nebulosity around SN1987A. This study will also strongly constrain the physical properties of interstellar dust in the Large Magellanic Cloud. ================================================================================ Proposal Category: GO Scientific Category: Solar System ID: 9112 Title: Composition of Saturn's rings, and its variation with location PI: Dale Cruikshank PI Institution: Ames Research Center Saturn's rings have been a playground for dynamicists during the two decades since Voyager, and a variety of fascinating processes and structures have been identified and studied. One surprise has been that the ring system seems to be evolving dynamically and compositionally on geologically short timescales, and might be much younger than the solar system. However, there has been very little progress in understanding the composition of the rings during this time. While water ice is known to be the dominant constituent, the reddish color of the rings requires there to be other material there. Furthermore, studies of Voyager and HST-WFPC2 color images indicate that the ring color (and presumably therefore composition) varies dramatically from region to region, and has complex correlations with ring structure. Unfortunately, these multicolor observations are incapable of identifying specific constituents spectrally. The only existing moderate spectral resolution observations, on the other hand, have been ring-averages and smear all the diverse spectral contributions together. With STIS, we propose to separate out the known spatial-spectral variability with sufficient spectral resolution to make identifications of specific constituents. This will allow us to truly study the processes responsible for compositional evolution. It will also provide an excellent preparation and foundation for planning Cassini observations of the rings. ================================================================================ Proposal Category: GO Scientific Category: Cool Stars ID: 9113 Title: Solar UV Radiation and the Origin of Life on Earth PI: Sara R. Heap PI Institution: Goddard Space Flight Center Prior to 3.5 Gyr ago when life arose on Earth, the ultraviolet emission of the early Sun was more intense than at present. This radiation helped shape the chemical environment of the early Earth and hence influenced prebiotic evolution, the origin of life, and its subsequent early development. We propose to investigate this UV emission by making an efficient, systematic study of the UV spectra of 8 stars believed to resemble the early Sun. beginitemize em We will use the observed UV flux distributions as boundary conditions in photochemical models of the Earth's atmosphere, in order to estimate the concentrations of greenhouse gases and other molecules that may have played a major role in the origin of life. em We will also use the spectra to construct semi-empirical models of the chromospheres of these young solar analogs. The chromospheric models will enable us to predict the extreme- UV emission of the early Sun and its consequences for the erosion of the early Earth's atmosphere and the altered oxidation state of the planet. em We will investigate the effect of metallicity on the UV emission and its consequences for the photochemistry of Earth-like planets. enditemize ================================================================================ Proposal Category: GO Scientific Category: Hot Stars ID: 9114 Title: SINS: The Supernova INtensive Study--Cycle 10 PI: Robert Kirshner PI Institution: Harvard College Observatory Supernovae create the chemical history of the Universe, energize the interstellar gas, stiffen the spine of the extragalactic distance scale and provide the only evidence for an accelerating universe. SINS is a program to study supernovae with HST: perfectly matched in field and scale for spatially- resolved observations of SN 1987A. There, a violent encounter is underway between the fast-moving debris and the stationary inner ring, as predicted by our team members and first observed by us. Monitoring this interaction will help solve the riddles of stellar evolution posed by the enigmatic three-ring system of SN 1987A. Our UV observations of Ly-Alpha emission reveal the present location and velocity of a remarkable reverse shock that provides a unique laboratory for studying fast shocks and a powerful tool for dissecting the structure of the vanished star. For more distant events, we propose Target-of-Opportunity observations. In addition to one bright new supernova in Cycle 10 (discovered by any search,) we propose to discover two supernovae for study in the ultraviolet at times specificed in advance, using the world's most effective automated search system: the Lick Observatory Supernova Search. SINS will study the historic SN 1987A, explore UV emission from distant supernovae, and press late-time observations of supernovae into uncharted territory of infrared catastrophes, light echos, and stellar remnants. ================================================================================ Proposal Category: GO Scientific Category: Stellar Populations ID: 9115 Title: The Evolution of Extreme Gas Rich Galaxies PI: Patricia Knezek PI Institution: Space Telescope Science Institute We propose to observe a recently discovered sample of the closest known low surface brightness (LSB), very gas-rich dwarf galaxies outside of the Local Group. These galaxies represent an extreme star formation environment, where the fuel for star formation appears plentiful, the local environment (the Centaurus A group of galaxies) provides opportunities for tidally-induced star formation, and yet star formation appears to be surpressed (by two orders of magnitude) compared to other `typical' galaxies. Our goal is to understand the star formation history in this puzzling environment of low stellar density and high gas content. By resolving the underlying stellar component with WFPC2, we will obtain critical information on the mean metallicity and star formation history of these galaxies. The HST data will be combined with a vigorous ground-based program to study the ongoing massive star formation rate and the mean age of the stellar population, through a combination of broadband (UBVRI) and narrowband (H-alphapha and S II) imaging. The combined data sets will help us understand the star formation process in these extreme gas-rich LSB galaxies, and in gaseous galaxies in general. Such knowledge is key for our comprehension of the present day role of the most common type of potentially star forming galaxies in the Universe, and may aid us in interpreting results at high redshifts on star formation in the early universe. ================================================================================ Proposal Category: GO Scientific Category: Hot Stars ID: 9116 Title: Understanding high-redshift and starburst galaxies: A UV spectroscopic survey of B-stars in the SMC PI: Daniel Lennon PI Institution: Isaac Newton Group Telescopes In Cycle 7 we successfully applied to carry out a high resolution UV spectroscopic survey of O-stars in the SMC. The primary aim of this program, GO-7437, is to construct a high quality spectral library at low metallicity in order to synthesize the UV spectra of high redshift star-forming galaxies and nearby starbursts. This program is almost completed and in the present proposal we ask to extend the survey to B-stars in the SMC. There are important reasons for doing so. Chief among these is that recent work, some of it prompted by GO-7437 results, indicates that B-stars are significant contributors to the observed UV spectrum of high redshift galaxies such as the important MS 1512-cB58. In the present survey we also propose to extend the wavelength coverage into the near-UV in order to cover the most distinguishing feature in B-star UV spectra, the Fe, iii multiplet between 1900 and 2000Angstrom . This feature is a key diagnostic of B-stars and an excellent discriminant against O-stars. The combined survey of O and B stars will constitute the definitive UV spectral library of massive stars at low metallicity and will offer powerful diagnostic capabilities in many other areas of astronomy, particularly in the area of massive star evolution and its dependence on metallicity and rotation. ================================================================================ Proposal Category: GO Scientific Category: Galaxies ID: 9117 Title: Spatially Resolved Spectroscopy of Super Star Clusters in the M82 Starbursts PI: Robert O'Connell PI Institution: University of Virginia M82 is the prototype starburst galaxy and the nearest analogue to the star forming galaxies recently identified at high redshifts. There is good evidence that M82 has experienced multiple starburst episodes over the past ~ 800 Myr. No other galaxy affords the opportunity to study both an active starburst and the subsequent post-burst phase at such close range (3.6 Mpc) and with such a wealth of complementary data from other space and ground-based telescopes. In our Cycle 1 and 7 HST imaging programs on M82, we identified numerous super star clusters, which seem to be hallmarks of intense star formation. We propose to obtain spatially-resolved STIS spectroscopy of 20 such clusters in M82's active starburst core and also in its ``fossil'' starburst region (of age >~ 200 Myr) as a means of tracing the history of star formation and its propagation. With the spatially-resolved spectra, we will be able to study the internal structure of the clusters, evidence for internal mass segregation, their interaction with their surroundings (including M82's superwind), and the character of the bright, diffuse non-cluster populations. ================================================================================ Proposal Category: GO Scientific Category: Cosmology ID: 9118 Title: Tracing the Cosmic Ex