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Date and Time of the Query: 2019-05-26 T06:03:54 PDT
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For refcode 1989ApJ...347..875S:
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Copyright by American Astronomical Society. Reproduced by permission
1989ApJ...347..875S OXYGEN ABUNDANCES IN NEARBY DWARF IRREGULAR GALAXIES EVAN D. SKILLMAN Astronomy Department, University of Texas R. C. KENNICUTT Steward Observatory, University of Arizona AND P. W. HODGE Astronomy Department, University of Washington Received 1988 September 22; accepted 1989 June 19 ABSTRACT Oxygen abundances are obtained by optical spectrophotometry of H II regions in seven nearby dwarf irregular galaxies. All of these yield oxygen abundances of less than 1/10 of the solar value, and most are in the range of 3%-5% of the solar value. This suggests that observations of nearby dwarf galaxies may provide an effective means for studying the chemical evolution of low-mass galaxies and, possibly, the primordial helium abundance. In one case, a planetary nebula (PN) was discovered. A strong correlation is found between the oxygen abundances and absolute magnitudes for nearby irregular galaxies. This correlation will be useful for estimating abundances of irregular galaxies without observable H II regions, and possibly as a distance indicator for irregular galaxies with known abundances. It is inferred from this relationship that infall is no more important in irregular galaxies with extremely large H I halos than in typical irregular galaxies. Dwarf ellipticals closely adhere to the abundance-luminosity relationship defined by irregulars. The similar abundance-luminosity relationships may be taken as support of the popular theory that dwarf ellipticals are formed by stripping the gaseous component of dwarf irregular galaxies. Subject headings: galaxies: abundances - nebulae: H II regions - nebulae: planetary
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