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Paper: Spectral evolution of cluster galaxies
Volume: 10, Evolution of the Universe of Galaxies: Edwin Hubble Centennial Symposium
Page: 200
Authors: Dressler, Alan; Gunn, James E.
Abstract: There is strong evidence for spectral evolution of galaxies in rich clusters since z is approximately equal to 0.5. Studies of 14 clusters at z in the range between 0.20 and 0.55 by several different groups have consistently revealed a higher incidence of galaxies active in star formation compared to similar low-z clusters. Detection of spectral characteristics rare in present-epoch galaxies suggest that this enhanced star formation may have occurred in bursts, perhaps triggered by the first interaction of a gas-rich galaxy with the hot intracluster gas. As such this type of activity may be mainly the result of environmental influence rather than pure galactic evolution with cosmic time. However, new observations of the amplitude of the 4000 A break obtained by Dressler and Gunn indicate that by z greater than approximately 0.7 even the reddest (presumably oldest) cluster galaxies show evidence of evolution. This places a limit of the bulk of star formation z in the range between 2 and 5 for these galaxies.
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