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:
- variations of different elements (the alpha element problem)
- HB effects on the H-beta index
- spectroscopic measurements are limited to the bright core regions, and only nearby
clusters
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.
