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Astron. Astrophys. 358, 535-546 (2000)


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Self-enrichment in [FORMULA] Centauri

C. Ikuta and N. Arimoto

Institute of Astronomy, School of Science, University of Tokyo, Mitaka, Tokyo 181-8588, Japan

Received 2 July 1999 / Accepted 19 November 1999

Abstract

The origin of abundance spreads observed in [FORMULA] Centauri is studied in the context of the self-enrichment scenario. Five chemical evolution models are constructed and are compared with empirical metallicity distribution of [FORMULA] Cen. After a series of simulations, it is found that neither of closed-box, outflow, nor infall models can reproduce the empirical metallicity distribution of [FORMULA] Cen, while a modified outflow model with a bimodal initial mass function (IMF) gives a metallicity distribution that fits closely to the empirical ones. In the modified outflow model, long-lived stars are assumed to form after the first explosion of type II supernovae (SNII) in a proto-cloud. The modified outflow model involves gas infall at the very first chemical evolution. Thus we conclude that self-enrichment causes the abundance dispersion in [FORMULA] Cen. A success of the outflow model with the bimodal IMF implies that low mass stars in a globular cluster (GC) should have formed in the gas already enriched by the first generation of SNII.

This scenario, originally proposed by Cayrel (1986), can explain a lack of globular clusters with [Fe/H][FORMULA] in the Milky Way Galaxy.

Key words: Galaxy: globular clusters: general – Galaxy: globular clusters: individual: ! Centauri – stars: abundances – stars: Population II – galaxies: abundances – galaxies: evolution

Send offprint requests to: C. Ikuta

© European Southern Observatory (ESO) 2000

Online publication: June 8, 2000

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