Energy Distributions and the Formation Times of Spheroidal Populations

Abstract

I review recent progress in exploring the formation times of spheroidal stellar populations (elliptical galaxies and large spiral bulges) using spectrophotometric techniques. A quickly growing body of evidence shows that although massive spheroids can form at early times, there are strong environmental dependencies, and major transitions in star formation histories and even morphologies are detectable to surprisingly small redshifts (z ~ 0.2). These features are consistent with neither the strict monolithic collapse nor hierarchical merging scenarios. Restframe UV observations are a promising means of improving our understanding of spheroid evolution.