The Galactic Disk-Halo transition - Evidence from Stellar Abundances
arXiv:0807.3831 · doi:10.1017/S1743921308027452
Abstract
New information on the relations between the Galactic disks, the halo, and satellite galaxies is being obtained from elemental abundances of stars having metallicities in the range -1.5 < [Fe/H] < -0.5. The first results for a sample of 26 halo stars and 13 thick-disk stars observed with the ESO VLT/UVES spectrograph are presented. The halo stars fall in two distinct groups: One group (9 stars) has [alpha/Fe]= 0.30 +-0.03 like the thick-disk stars. The other group (17 stars) shows a clearly deviating trend ranging from [alpha/Fe]= 0.20 at [Fe/H]= -1.3 to [alpha/Fe]= 0.08 at [Fe/H]= -0.8. The kinematics of the stars are discussed and the abundance ratios Na/Fe, Ni/Fe, Cu/Fe and Ba/Y are applied to see if the low-alpha stars are connected to the thin disk or to Milky Way satellite galaxies. Furthermore, we compare our data with simulations of chemical abundance distributions in hierarchically formed stellar halos in a LambdaCDM Universe.
6 pages, 6 figures. To appear in proceedings of the IAU Symposium No. 254 "The Galaxy Disk in Cosmological Context", Copenhagen 9-13 June 2008, Eds. J. Andersen, J.Bland-Hawthorn & B. Nordstrom, Cambridge University Press
References in corpus (7)
- Elemental Abundance Survey of The Galactic Thick Disk
- alpha-, r-, and s-process element trends in the Galactic thin and thick disks
- The exotic chemical composition of the Sagittarius dwarf Spheroidal galaxy
- Chemical Abundance Distributions of Galactic Halos and their Satellite Systems in a Lambda CDM Universe
- Complexity on Small Scales III: Iron and alpha Element Abundances in the Carina Dwarf Spheroidal Galaxy
- Chemical abundances in LMC stellar populations I. The Inner disk sample Based on observations collected at the VLT UT2 telescope
- uvby-βphotometry of high-velocity and metal-poor stars XI. Ages of halo and old disk stars