Star formation and chemical abundances in the blue compact galaxy ESO338-IG04.

Abstract

The blue compact galaxy ESO 338 - IG04, which is undergoing a burst of star formation, is luminous for its type and has extremely blue colors. Attention is given to new broadband UBVIR photometry, spectroscopy, and both direct photographic and CCD observations of this galaxy, together with the reanalysis of a low resolution IUE spectrum. In H-alpha, three prominent central condensations and a spiral arm structure are revealed. Although hot stars are noted to be the most important ionization source, small amounts of shock-heated gas may be present. As an aid in the analysis of the stellar content, a simple model of the color evolution of a metal-poor galaxy is used. During the last two years, the galaxy seems to have brightened considerably, especially in the V band.