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Astron. Astrophys. 320, 41-53 (1997)

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Origin of the colour-magnitude relation of elliptical galaxies

Tadayuki Kodama 1 and Nobuo Arimoto 1, 2, 3

1 Institute of Astronomy, University of Tokyo, Mitaka, Tokyo 181, Japan
2 Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge, CB3 0HA, UK
3 Department of Physics, University of Durham, South Road, Durham, DH1 3LE, UK

Received 11 June 1996 / Accepted 13 September 1996


Evolutionary models of elliptical galaxies are constructed by using a new population synthesis code. Model parameters are calibrated to reproduce the observed colour-magnitude (CM) relation of Coma ellipticals in [FORMULA] vs. [FORMULA] diagram. The SEDs are degenerated in stellar age and metallicity. An attempt is performed to break this degeneracy, by simulating evolution of the CM relation of elliptical galaxies, based on the two alternative interpretations; i.e., the CM relation reflects different mean stellar age or various stellar metallicity. A confrontation with the CM diagrams of E/S0 galaxies in the two distant clusters Abell 2390 ([FORMULA]) and Abell 851 ([FORMULA]) reinsures previous contentions that the CM relation is primarily a metallicity effect. This conclusion does not depend either on the model parameters, or on the cosmological parameters adopted.

Key words: galaxies: elliptical – galaxies: evolution – galaxies: formation – galaxies: photometry – galaxies: stellar content

Send offprint requests to: T. Kodama

© European Southern Observatory (ESO) 1997

Online publication: July 3, 1998