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H. Lee, E. K. Grebel (Max-Planck-Institute for Astronomy), P. W. Hodge (Astronomy Dept., University of Washington)
As part of an ongoing survey of dwarf galaxies within the Local Volume (< 5~Mpc), extensive photometric and spectroscopic observations are being conducted with the HST and ground-based telescopes. New optical spectroscopic data have been obtained of H~II regions in 17 southern dwarf irregular galaxies, including those in the Centaurus~A group, the Sculptor group, the Local Group, and the field. A majority of the dwarfs are metal-poor with oxygen abundances, 12+log(O/H), in the range between 7.4 and 8.0 (approximately 5% to 20% of solar). ESO358-G060 has an oxygen abundance comparable to that of the second most metal-poor dwarf galaxy known (SBS0335-052). Oxygen abundances for dwarfs in the present sample are consistent with the metallicity-luminosity relationship defined by nearby dwarf irregulars. However, upon comparison with the nearby sample, a number of objects in the present sample have lower MH I/LB values at a given abundance and luminosity. These objects may be in fact gas-poor, have strong bursts whose luminosities are biasing MH I/LB, and/or are evolving as ``closed boxes'' with oxygen yields one-tenth of the solar value.
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Bulletin of the American Astronomical Society, 34, #4
© 2002. The American Astronomical Soceity.