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

Self-enrichment in 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 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 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 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 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] 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

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Contents

• 1. Introduction
• 2. The observed metallicity distribution
• 3. Theoretical metallicity distribution
  • 3.1. Closed box and outflow models
  • 3.2. Infall model
  • 3.3. Models with a bimodal IMF
    • 3.3.1. Bimodal IMF
    • 3.3.2. Model involving infall
• 4. Discussion
  • 4.1. Abundance gradient
  • 4.2. Enrichment in GCs
• 5. Conclusion
• Acknowledgements
• References

© European Southern Observatory (ESO) 2000

Online publication: June 8, 2000
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