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Date and Time of the Query: 2019-05-26 T18:28:37 PDT
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For refcode 2001AJ....122.2318B:
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2001AJ....122.2318B HIGH AND LOW SURFACE BRIGHTNESS GALAXIES IN THE LOCAL UNIVERSE. V. OPTICAL AND H I PROPERTIES VALORIE BURKHOLDER AND CHRIS IMPEY Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721; veburkholder@west.raytheon.com, cimpey@as.arizona.edu AND DAVID SPRAYBERRY W. M. Keck Observatory, 65-1120 Mamalahoa Highway, Kamuela, HI 96743; dsprayberry@keck.hawaii.edu Received 2001 April 18; accepted 2001 July 25 ABSTRACT Using optical spectra of the nuclei of 250 galaxies chosen from the Automated Plate Measuring Facility (APM) survey of UK Schmidt plates, we derive synthetic B-V and V-R colors, estimates of reddening from Balmer decrements, metallicity via oxygen abundance, and star formation rate from the H{alpha} luminosity. We also present mass-to-light ratios and gas mass fractions from 21 cm H I measurements of 238 APM survey galaxies, 101 of which also have optical spectra. This sample of galaxies spans a large range in surface brightness, from high surface brightness irregular galaxies down to the kind of low surface brightness (LSB) galaxies that are missing from most magnitude-limited catalogs. The generally blue global colors are best explained by a combination of low metallicity and active star formation, primarily because of the tremendous scatter in metallicity versus B-V. Optical spectra show the presence of G and K main-sequence stars in the nuclei of these galaxies, and the stellar mass-to-light ratios and gas mass fractions show the galaxies as a whole to be gas-rich. LSB galaxies are most likely to experience sporadic low levels of star formation over gigayear timescales. Key words: galaxies: abundances - galaxies: fundamental parameters - galaxies: general - galaxies: ISM - galaxies: nuclei - galaxies: stellar content
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