The Oxygen Abundance of Nearby Galaxies from Sloan Digital Sky Survey Spectra
Abstract
We have derived the oxygen abundance for a sample of nearby galaxies in the Data Release 5 of the Sloan Digital Sky Survey (SDSS) which possess at least two independent spectra of one or several HII regions with a detected [OIII]4363 auroral line. Since, for nearby galaxies, the [OII]3727 nebular line is out of the observed wavelength range, we propose a method to derive (O/H)ff abundances using the classic Te method coupled with the ff relation. (O/H)7325 abundances have also been determined, based on the [OII]7320,7330 line intensities, and using a small modification of the standard Te method. The (O/H)ff and (O/H)7325 abundances have been derived with both the one- and two-dimensional t2 - t3 relations. It was found that the (O/H)ff abundances derived with the parametric two-dimensional t2 - t3 relation are most reliable. Oxygen abundances have been determined in 29 nearby galaxies, based on 84 individual abundance determinations in HII regions. Because of our selection methods, the metallicity of our galaxies lies in the narrow range 8.2 < 12 + log (O/H) < 8.4. The radial distribution of oxygen abundances in the disk of the spiral galaxy NGC 4490 is determined for the first time.
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