Continuum Colors of Galaxy Populations in Rich Clusters

James Schombert
Univ. of Oregon

Karl Rakos
Univ. of Vienna

This is an ongoing project (from the mid-1980's) to use the narrow band Stromgren system (uvby) for the study of the stellar populations and color evolution of galaxies. Our observations have focused on three areas of study: 1) estimate the mean metallicity and age of nearby cluster ellipticals as a function of mass (luminosity), 2) color evolution of the red population in clusters (ellipticals) with redshift, and 3) characterizing the Butcher-Oemler effect in intermediate redshift clusters.

The last five years has seen a burst of high resolution spectra which use various lines (Fe 5341, Mg b, H-beta) to determine the mean metallicity and age of the underlying stellar population (Trager et al 2001, Kunschter et al 2001). However, spectroscopic measurements have several difficulties in their interpretation:

We have followed a parallel path to the spectroscopic studies by focusing on those regions of the SED in galaxies which are relatively free of line effects (continuum) and special regions where line effects are cumulative.