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Evolution of the colour-magnitude relation of early-type galaxies in distant clusters

T. Kodama·N. Arimoto·A. J. Barger·A. Aragon-Salamanca
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Abstract

We present a thorough quantitative analysis of the evolution of the colour-magnitude relation for early-type galaxies in 17 distant clusters with redshifts 0.31 < z < 1.27 using the Kodama & Arimoto (1997) evolutionary model for elliptical galaxies. The model is calibrated to reproduce the colour- magnitude relation for Coma ellipticals at z ~ 0 and gives the evolution of the slope and zero-point as a function of redshift. We find no significant differences between the colour-magnitude relations of the clusters in our sample. The slopes can be reproduced by a single model sequence in which all elliptical galaxies are assumed to be equally old (the maximum age difference allowed for the brightest 3 magnitudes is only 1 Gyr) and to have mean stellar metallicities which vary as a function of galaxy luminosity. The zero-points of the colour-magnitude relations constrain the epoch of major star formation in early-type galaxies to z_f>2-4. This study provides two important constraints for any model of the formation of rich clusters: the uniformity of the ages of the stellar populations in the early-type galaxies and the universality of the metallicity sequence of these galaxies as a function of galaxy mass.

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T. Kodama, N. Arimoto, A. J. Barger, A. Aragon-Salamanca. 1998-02-18. Evolution of the colour-magnitude relation of early-type galaxies in distant clusters. https://arxiv.org/abs/astro-ph/9802245

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