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A. Y. Kniazev, E. K. Grebel (MPIA), L. Hao, M. A. Strauss (Princeton U.)
The SDSS spectroscopic database, which will ultimately contain spectra of one million galaxies, provides an ideal resource for searches for extremely low-metallicity galaxies. Using the current version of the database we studied 135,000 galaxy spectra to calculate the oxygen abundance. We used only spectra in which the [OIII] 4363 Å\ line was detected. Among this vast number of galaxies, we discovered only one new extremely metal-poor galaxy: SDSS~J0519+0007. It has an oxygen abundance of only 12+log(O/H) = 7.45 ±0.02 or 1/30 of our Sun. This makes it the sixth galaxy in the short list of very metal-poor galaxies, and the first one discovered with SDSS data. We derived abundances of O, Ne, Ar, N, S, and He for SDSS~J0519+0007. Abundance ratios for \alpha-elements for this galaxy are in good agreement with the mean values for other very metal-deficient blue compact galaxies (except for nitrogen). The broad low-contrast component in the H\alpha emission line indicates the presence of fast motions in this galaxy. We also detect the characteristic blue bump, a signature of Wolf-Rayet stars, in the SDSS spectrum. SDSS~J0519+0007 is a new low-metallicity dwarf galaxy with a luminosity of MB ~-18 mag (redshift 0.044). This is more than 3 mag brighter than any previously known galaxy of such low metallicity and indicates that such objects may span a total range of luminosities of more than 6 magnitudes.
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Bulletin of the American Astronomical Society, 34
© 2002. The American Astronomical Soceity.