The star formation history of early-type galaxies

Abstract

The UV light is an effective tracer for young stars. Base on the recent GALEX UV data of nearby, bright early-type galaxies, we find that 30% of them show a UV flux that is too strong to explain without invoking a 1-3% (in total stellar mass) star formation rate in the last billion years. This implies that low-level residual star formation was common during the last few billion years even in bright, early-type galaxies. We discuss the implications for the formation and evolution of early-type galaxies. This article is a summary of our recent work (Yi et al. 2005; Schawinski et al. 2006; Kaviraj et al. 2006).