Journal Article

Two groups within the thick disc of the Milky Way?

Laura M. Stanford and David L. Lambert

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 424, issue 3, pages 2118-2129
Published in print August 2012 | ISSN: 0035-8711
Published online August 2012 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2012.21364.x
Two groups within the thick disc of the Milky Way?

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Abstract

Compositions of F and G dwarf stars in two groups of thick disc stars are presented. The groups identified by Schuster et al. have mean characteristics ([Fe/H], V(rot), Age, ) of (−0.7 dex, 120 km s−1, 12.5 Gyr, 62 km s−1) and (−0.4, 160, 10.0, 45.8). Abundances for 23 elements obtained from high-resolution spectra are presented for 59 stars in the metal-rich group and 27 stars in the metal-poor group. The run of abundance ratios [X/Fe] versus [Fe/H] for the two groups define a single relation for each element (designated as X) with no intrinsic scatter and without a measurable discontinuity at −0.6 < [Fe/H] < −0.5, the metallicity at which the two groups overlap. The relations [X/Fe] versus [Fe/H] are those determined previously for thick disc stars. It is suggested that these two groups and the thick disc as a whole have a common origin in terms of prior chemical evolution.

Keywords: stars: abundances; Galaxy: disc

Journal Article.  3591 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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