The stellar ages of elliptical galaxies

Integrated broad-band colors and metallic lines cannot discriminate clearly between the effects of age and Z in old stellar populations. Such data are more sensitive to Z than to age. The H beta feature provides a way to brea k this degeneracy. New measurements indicate that the mean stellar ages of typical E galaxy nuclei are fairly young, ranging from 2 to similar to 12 G yr. The outer parts of E galaxies are both older and more metal-poor than n uclei, consistent with the formation of E galaxies via mergers and starburs ts. Age effects contribute strongly to the classic color-line strength sequ ence of E galaxies.