Multiple and Strong Luminosity Evolution in the Population of Elliptical Galaxies**The project supported by National Natural Science Foundation of China

Abstract

The traditional single burst and passive evolution model for elliptical galaxies should not be accepted. In this paper we demonstrate further by comparison of the model predictions with the observed B–K color distribution of galaxies, that the internal extinction by dust cannot save the traditional scenario for ellipticals either. Hence we do not agree with Zepf's (S.E. Zepf, Nature 390 (1997) 377) argument that such a scenario could still survive if ellipticals might have formed in dusty starburst environments. Furthermore, we have also found that the luminosity evolution within the population of ellipticals should be strong, complicated or multiple, which is not favored by our previous study of number counts for ellipticals. The conflicting results simply suggest that the pure luminosity evolution model should not be accepted, and hence the number evolution for ellipticals is a straightforward inference. Our conclusions hold in any one of the three cosmological models, i.e., flat, open, or -dominated, under consideration.