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Evolution of Cluster Early-Type Galaxies

P. G. van Dokkum·M. Franx·D. D. Kelson·G. D. Illingworth·D. Fabricant
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Abstract

The slow evolution of the M/L ratios, colors, and line strengths of cluster early-type galaxies to z=1 suggests that their stars were formed at very high redshift. At the same time, morphological studies of distant clusters indicate significant evolution in the early-type galaxy population. Striking evidence for strong morphological evolution in clusters is the discovery of a large number of red merger systems in the cluster MS 1054-03 at z=0.83. The presence of these mergers is qualitatively consistent with predictions from hierarchical galaxy formation models, and is direct evidence against an early collapse for all early-type galaxies. In most of the mergers there is no evidence for strong star formation. Therefore the mean stellar ages of the merger products will be much older than the ``assembly age'', and do not violate the constraints on the star formation epoch of early-type galaxies imposed by the color-magnitude relation and the Fundamental Plane.

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P. G. van Dokkum, M. Franx, D. D. Kelson, G. D. Illingworth, D. Fabricant. 2000-12-05. Evolution of Cluster Early-Type Galaxies. https://arxiv.org/abs/astro-ph/0012090

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