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Astron. Astrophys. 362, 921-936 (2000)

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Abundance gradients and their evolution in the Milky Way disk

J.L. Hou 1,2,3,4, N. Prantzos 2 and S. Boissier 2

1 Shanghai Astronomical Observatory, CAS, Shanghai, 200030, P.R. China (hjlyx@center.shao.ac.cn)
2 Institut d'Astrophysique de Paris, 98bis, Bd. Arago, 75014 Paris, France (prantzos@iap.fr)
3 National Astronomical Observatories, CAS, P.R. China
4 Joint Lab of Optical Astronomy, CAS, P.R. China

Received 16 May 2000 / Accepted 26 July 2000

Abstract

Based on a simple, but fairly successful, model of the chemical evolution of the Milky Way disk, we study the evolution of the abundances of the elements He, C, N, O, Ne, Mg, Al, Si, S, Ar and Fe. We use metallicity dependent yields for massive stars with and without mass loss. We find that most observed abundance profiles are correctly reproduced by massive star yields, but C and N require supplementary sources. We argue that massive, mass losing stars can totally account for the abundance profile of C, while intermediate mass stars are the main source of N; in both cases, some conflict with corresponding data on extragalactic HII regions arises, at least if current observations in the Galaxy are taken at face value. The observed behaviour of Al is marginally compatible with current massive star yields, which probably overestimate the "odd-even" effect. We also find that the adopted "inside-out" formation scheme for the Milky Way disk produces abundance profiles steeper in the past. The corresponding abundance scatter is smaller in the inner disk than in the outer regions for a given interval of Galactic age.

Key words: stars: abundances – nuclear reactions, nucleosynthesis, abundances – Galaxy: abundances – Galaxy: evolution

Send offprint requests to: N. Prantzos

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© European Southern Observatory (ESO) 2000

Online publication: October 30, 2000
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