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Date and Time of the Query: 2019-07-15 T23:46:01 PDT
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For refcode 1990AJ.....99..530B:
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1990AJ.....99..530B THE STELLAR POPULATIONS OF EARLY-TYPE GALAXIES AS A FUNCTION OF THEIR ENVIRONMENT RICHARD G. BOWER AND RICHARD S. ELLIS Department of Physics, University of Durham, Durham DH 1 3LE, United Kingdom JAMES A. ROSE Department of Physics and Astronomy, University of North Carolina, Chapel Hill, North Carolina 27599 RAY M. SHARPLES Anglo-Australian Observatory, P.0. Box 296, Epping NSW 2121, Australia Received 21 July 1989;revised 2 November 1989 ABSTRACT We have used gravity-sensitive spectral indices in the blue spectral region to study the mean stellar surface gravity of early-type galaxies in a variety of galaxian environments. We confirm earlier work that the mean surface gravity in integrated light is high for isolated and Virgo Cluster E/S0 galaxies, but find evidence to suggest that the mean surface gravity for similar galaxies in rich clusters is significantly lower. This indicates that galaxies in dense environments may be older on average than their counterparts in lower-density regions. Possible selection effects and systematic errors are discussed. We conclude that star formation in galaxies was truncated at an earlier epoch (on average) in dense environments, but note that the strength of our result would be weakened if there were large "age" gradients within these galaxies.
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