The [Zn/Fe] – [Fe/H] trend for disk and halo stars

Free access article

Issue		A&A Volume 425, Number 2, October II 2004


Page(s)		697 - 705
Section		Stellar atmospheres
DOI		http://dx.doi.org/10.1051/0004-6361:20047191

A&A 425, 697-705 (2004)
DOI: 10.1051/0004-6361:20047191

The [Zn/Fe] - [Fe/H] trend for disk and halo stars

Y. Q. Chen¹, P. E. Nissen² and G. Zhao¹

¹ National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012, PR China
e-mail: [cyq;zg]@bao.ac.cn
² Institute of Physics and Astronomy, University of Aarhus, 8000 Aarhus C, Denmark
e-mail: pen@phys.au.dk

(Received 4 February 2004 / Accepted 17 June 2004)

Abstract
Zn abundances, derived from a model atmosphere analysis of the $\lambda$ 6362.35 Å $\ion{Zn}{i}$ line, are presented for 44 thin disk, 10 thick disk and 8 halo dwarf stars in the metallicity range $-1.0 < \mbox{\rm [Fe/H]}< +0.2$ . It is found that [Zn/Fe] in thin disk stars shows a slight increasing trend with decreasing metallicity reaching a value $\mbox{\rm [Zn/Fe]}\simeq +0.1$ at $\mbox{\rm [Fe/H]}= -0.6$ . The thick disk stars in the metallicity range $-0.9 < \mbox{\rm [Fe/H]}< -0.6$ have an average $\mbox{\rm [Zn/Fe]}\simeq +0.15$ dex, whereas five alpha-poor and Ni-poor halo stars in the same metallicity range have $\mbox{\rm [Zn/Fe]}\simeq 0.0$ dex. These results indicate that Zn is not an exact tracer of Fe as often assumed in abundance studies of damped Lyman-alpha systems (DLAs). A better understanding of the nucleosynthesis of Zn is needed in order to obtain more detailed information on the past history of star formation in DLAs from e.g. the observed sulphur/zinc ratio.

Key words: stars: abundances -- stars: atmospheres -- Galaxy: evolution -- Galaxy: solar neighbourhood -- galaxies: high-redshift

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