AAO Lecture Theatre

William Harris

The Ages of Elliptical Galaxies - William Harris Colloquium

Elliptical galaxies are complex mixes of stellar populations which probably formed from a combination of early starbursts and later satellite accretions and mergers. A powerful way to determine the internal age distribution of their stars and the enrichment history is by direct matching of the color-magnitude data for their halo stars to model distributions. Although this method is well understood in theory, it has become possible to apply in practice to E galaxies only because of superb new deep HST data. I will discuss the results we are finding for a range of small-to-large ellipticals including M32 in the Local Group, NGC 5128 in Centaurus, and NGC 3377 and 3379 in the Leo group. The answers emerging from our study reveal a surprisingly varied mix of histories.