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Astron. Astrophys. 350, 38-48 (1999)


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Two-component model for the chemical evolution of the Galactic disk

R.X. Chang 1,2,3, J.L. Hou 1,2,3, C.G. Shu 1,2,3 and C.Q. Fu 1,2,3

1 Shanghai Astronomical Observatory, Chinese Academy of Sciences, Shanghai, 200030, P.R. China
2 National Astronomical Observatories, Chinese Academy of Sciences, P.R. China
3 United Lab for Optical Astronomy, Chinese Academy of Sciences, P.R. China

Received 30 September 1998 / Accepted 26 May 1999

Abstract

In the present paper, we introduce a two-component model of the Galactic disk to investigate its chemical evolution. It is assumed that the formation of the thick and thin disks occurs in two main accretion episodes with both infall rates being Gaussian. Both the pre-thin and post-thin scenarios for the formation of the thick disk are considered. The best fit is obtained through [FORMULA]-test between the models and the new observed metallicity distribution function of G dwarfs in the solar neighbourhood (Hou et al. 1998). Our results show that, the predictions of both the pre-thin and post-thin model agree well with the new observed G-dwarf metallicity distribution, i.e., it is difficult to conclude which one is better when based on current observational constraints. However, the present-day local density of the thick disk, required for the pre-thin model to get the best fit, is larger than most of results from star counts, yet this disagreement does not exist for the post-thin model. From this point of view, it would seem that the post-thin model is more viable. Finally, other comparisons between model predictions and observations are given.

Key words: Galaxy: abundances – Galaxy: evolution – Galaxy: formation – Galaxy: structure

Send offprint requests to: R.X. Chang (crx@center.shao.ac.cn)

© European Southern Observatory (ESO) 1999

Online publication: September 24, 1999

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