Oxygen Abundance Distribution in a New Well-Selected Sample of Blue Compact Galaxies

Abstract

We present first results of spectrophotometry with the 6-m Russia telescope of a new sample of BCGs. The candidates were found on the digitized objective-prism photoplates of the Hamburg Quasar Survey by selecting objects with a high probability to be strong [Ont] λ5007 Å emitters. The intensity of the [010] λ4363 Å line was measured in all observed galaxies, allowing to determine directly the temperature in the Ho regions and to derive their oxygen abundances. In the sample log(0/H)+12 varies in the range of 7.6 to 8.4. A complete sample of 46 BCGs with an EW([0III])_λ5007 ≥ 100 Å was constructed and used for statistical analysis. This sample and related volume limited subsamples were used to derive the observed distribution of 0/H. Using evolutionary synthesis models of star-formation bursts, we corrected the observed distribution for observational selection effects due to different values of EW(Hβ). This is a first attempt to reconstruct the real metallicity distribution among BCGs at modern epoch. An interesting additional result is a very high fraction of certain and probable WR galaxies in our sample.

Partially supported by the LOC and INTAS grant No. 97-0033.

Partially supported by the LOC and RFBR grant No. 00-02-26667.