Two groups within the thick disc of the Milky Way?
Article first published online: 10 JUL 2012
© 2012 The Authors Monthly Notices of the Royal Astronomical Society © 2012 RAS
Monthly Notices of the Royal Astronomical Society
Volume 424, Issue 3, pages 2118–2129, 11 August 2012
How to Cite
Stanford, L. M. and Lambert, D. L. (2012), Two groups within the thick disc of the Milky Way?. Monthly Notices of the Royal Astronomical Society, 424: 2118–2129. doi: 10.1111/j.1365-2966.2012.21364.x
- Issue published online: 1 AUG 2012
- Article first published online: 10 JUL 2012
- Manuscript Accepted: 22 MAY 2012
- Manuscript Received: 22 MAY 2012
- Robert A. Welch Foundation of Houston, TX. Grant Number: F-634
- stars: abundances;
- Galaxy: disc
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.