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Omega, Age, and H_0 Implications of Recent Hubble Space Telescope Data in the Coma Cluster
Baum, William A.
This paper presents a way of finding mutually consistent values of Omega_M, t_0, and H_0. This approach is illustrated using recent Coma Cluster distance data, together with recent Hipparcos data for RR Lyrae stars. The age of the universe is derived by two completely independent methods, both linked to the RR Lyrae stars. The two methods can be m…
Hubble Space Telescope Spectra of 3C 279: A Lyman Limit System at Low Redshift
Stocke, John T.; Blades, J. Chris; Penton, Steve +2 more
We present Hubble Space Telescope (HST) Faint Object Spectrograph spectra of the blazar 3C 279 obtained during two recent optical outbursts of this source, maximizing the sensitivity to weak foreground absorption systems at far-UV wavelengths for this sight line. Eighteen absorption systems were detected above an observed 3 sigma limiting equivale…
Parallaxes and Proper Motions of Prototypes of Astrophysically Interesting Classes of Stars
Kundu, Arunav; Trimble, Virginia
Hipparcos data are presented for 13 stars belonging to six different evolutionary types that present various puzzles. There are three FK Comae stars, one Wolf-Rayet binary, the ``galloping giant'' FG Sagittae, two high-velocity B stars, two runaway T Tauri stars, and four cataclysmic variables. Most of the numbers are of limited statistical signif…
The Centers of Early-Type Galaxies with HST. IV. Central Parameter Relations.
Gebhardt, Karl; Richstone, Douglas; Kormendy, John +7 more
We analyze Hubble Space Telescope surface-brightness profiles of 61 elliptical galaxies and spiral bulges (hereafter "hot" galaxies). The profiles are parameterized by break radius rβand break surface brightness 1β These are combined with central velocity dispersions, total luminosities, rotation velocities, and isophote shap…
Reddening and Star Formation in Starburst Galaxies
Calzetti, Daniela
The reddening properties and the star formation history of a sample of 19 starburst galaxies are investigated using multiwavelength spectroscopy and infrared broad band photometry. New photometric data in the J, H, and K bands of the central starburst regions are supplemented with previously published spectra, covering the wavelength range 0.12-2.…
The Panchromatic Starburst Intensity Limit at Low and High Redshift
Lehnert, Matthew D.; Heckman, Timothy M.; Meurer, Gerhardt R. +2 more
The integrated bolometric effective surface brightness S_e distributions of starburst are investigated for samples observed in 1. the rest frame ultraviolet (UV), 2. the far-infrared and \Hα, and 3. 21cm radio continuum emission. For the UV sample we exploit a tight empirical relationship between UV reddening and extinction to recover the bolometr…
M-Subdwarfs: Spectroscopic Classification and the Metallicity Scale
Gizis, John E.
We present a spectroscopic classification system for M-dwarfs and M-subdwarfs based on quantitative measures of TiO and CaH features in the region lambda lambda 6200 - 7400 Angstroms. Our sample of cool stars covers the range from solar metallicity stars to the most extreme subdwarfs known. Using synthetic spectra computed by Allard and Hauschildt…
Low-Mass Binaries and the Stellar Luminosity Function
Gizis, John E.; Reid, I. Neill
We present a new investigation of the influence of unresolved binaries on the form deduced for the stellar luminosity function from photometric parallax surveys. We have compiled a catalogue of photometry and binary statistics for stars known to be north of -30° declination and within 8 parsecs of the Sun, and have used these stars as a reference …
Evolution of the Galaxy Population Based on Photometric Redshifts in the Hubble Deep Field
Yee, H. K. C.; Lin, H.; Sawicki, M. J.
This paper presents the results of a photometric redshift study of galaxies in the Hubble Deep Field (HDF). The method of determining redshifts from broadband colors is described, and the dangers inherent in using it to estimate redshifts, particularly at very high z, are discussed. In particular, the need for accurate high-z spectral energy distr…
Younger and Brighter - New Distances to Globular Clusters Based on HIPPARCOS Parallax Measurements of Local Subdwarfs
Reid, I. Neill
We have used new parallax measurements, obtained by the Hipparcos satellite, of fifteen nearby, metal-poor stars to re-define the subdwarf main-sequence. All of these stars have parallaxes determined to an accuracy of at least 12%. Comparing these measurements against previous ground-based data for nine stars reveals a systematic offset of 5%, in …