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Optical and Ultraviolet Analyses of ZZ Ceti Stars and Study of the Atmospheric Convective Efficiency in DA White Dwarfs
Fontaine, G.; Bergeron, P.; Wesemael, F. +3 more
New high signal-to-noise optical spectrophotometry is presented for 22 ZZ Ceti stars. The atmospheric parameters (Teff log g) and the mass are derived for each object using new model atmospheres and synthetic spectra calculated within the mixing-length theory, as well as recent published mass-radius relationships. Various parameterizati…
The Gaseous Extent of Galaxies and the Origin of Lyman-Alpha Absorption Systems: A Survey of Galaxies in the Fields of Hubble Space Telescope Spectroscopic Target QSOs
Bowen, David V.; Lanzetta, Kenneth M.; Webb, John K. +1 more
We present initial results of an imaging and spectroscopic survey of faint galaxies in fields of Hubble Space Telescope spectroscopic target QSOs. The primary objectives of the survey are (1) to determine the incidence, extent, and covering factor of extended gaseous envelopes of luminous galaxies and (2) to determine the fraction of Lyα absorptio…
WFPC2 Studies of the Crab Nebula. I. HST and ROSAT Imaging of the Synchrotron Nebula
Casertano, Stefano; Ballester, Gilda E.; Crisp, David +18 more
We present images of the Crab synchrotron nebula obtained with the Wide Field and Planetary Camera 2 (WFPC2) on board the Hubble Space Telescope. These data are compared with ROSAT HRI images, and with 0."5 resolution Canada-France-Hawaii Telescope (CFHT) images previously published by van den Bergh & Pritchet (1989). These data strengthen the…
Canada-France Redshift Survey: Hubble Space Telescope Imaging of High-Redshift Field Galaxies
Crampton, David; Lilly, S. J.; Hammer, F. +3 more
Hubble Space Telescope B and I images are presented of 32 galaxies with secure redshifts in the range 0.5 < z < 1.2 from the Canada-France Redshift Survey, a complete sample of galaxies with 17.5 <= IAB <= 22.5. These galaxies exhibit the same range of morphological types as seen locally, i.e., ellipticals, spirals, and irregulars. The…
The Central Region in M100: Observations and Modeling
Knapen, J. H.; de Jong, R. S.; Beckman, J. E. +2 more
We present new high-resolution observations of the central region in the late-type spiral galaxy M100 (NGC 4321) supplemented by three-dimensional numerical modeling of stellar and gas dynamics, including star formation (SF). Near-infrared imaging has revealed a small bulge of 4" effective diameter; a 60" radial length stellar bar of moderate stre…
Deuterium and the Local Interstellar Medium Properties for the Procyon and Capella Lines of Sight
Ayres, Thomas R.; Savage, Blair D.; Brown, Alexander +3 more
We present Goddard High-Resolution Spectrograph observations of the interstellar H I and D I Lyα lines and the Mg II and Fe II resonance lines formed along the lines of sight toward the nearby stars Procyon (3.5 pc, l = 214°, b = 13°) and Capella (12.5 pc, l = 163°, b = 5°). New observations of Capella were obtained at orbital phase 0.80, when the…
The Intermediate Stellar Mass Population in R136 Determined from Hubble Space Telescope Planetary Camera 2 Images
Holtzman, Jon A.; Lynds, Roger; Light, Robert M. +3 more
We have analyzed Hubble Space Telescope (HST) images of the compact, luminous star cluster R136 in the LMC that were taken with the refurbished HST and new Wide Field/Planetary Camera. These images allow us to examine the stellar population in a region of unusually intense star formation at a scale of 0.01 pc. We have detected stars to 23.5 in F55…
The Evolution of C/O in Dwarf Galaxies from Hubble Space Telescope FOS Observations
Terlevich, E.; Terlevich, R.; Garnett, D. R. +5 more
We present UV observations of seven H II regions in low-luminosity dwarf irregular galaxies and the Magellanic Clouds obtained with the Faint Object Spectrograph on the Hubble Space Telescope (HST) in order to measure the C/O abundance ratio in the interstellar medium (ISM) of those galaxies. We measure both O III] 1666 A and C III] 1909 A in our …
The Morphological Mix of Field Galaxies to M I = 24.25 mag (b J approximately 26 mag) from a Deep Hubble Space Telescope WFPC2 Image
Keel, William C.; Driver, Simon P.; Windhorst, Rogier A. +3 more
We determine the morphological mix of field galaxies down to mI ~= 24.25 mag (mB ~ 26.0 mag) from a single ultradeep Hubble Space Telescope wide field planetary camera (WFPC2) image in both the V606 and the I814 filters. In total, we find 227 objects with mI <= 24.5 mag and classify these into three types: ellipticals (16%), early-type spirals …
Hubble Space Telescope Observations of the SN 1987A Triple Ring Nebula
Casertano, Stefano; Ballester, Gilda E.; Crisp, David +16 more
We have observed SN 1987A with the optically corrected WFPC2 on the Hubble Space Telescope both in emission lines and in the UV and optical continuum. The previously observed outer nebular structure is shown to be part of two closed unresolved loops. These loops were flash-ionized by the supernova itself. They are not caused by limb brightening of…