The assembly of the halo system of the Milky Way as revealed by SDSS/SEGUE – The CEMP star connection

¹ National Optical Astronomy Observatory, Tucson, AZ, USA
² Michigan State University and JINA, E. Lansing, MI, USA
³ Macquarie University, Sydney, Australia
⁴ INAF - Osservatorio Astronomico di Torino, Italy

^a e-mail: beers@noao.edu

Abstract

In recent years, massive new spectroscopic data sets, such as the over half million stellar spectra obtained during the course of SDSS (in particular its sub-survey SEGUE), have provided the quantitative detail required to formulate a coherent story of the assembly and evolution of the Milky Way. The disk and halo systems of our Galaxy have been shown to be both more complex, and more interesting, than previously thought. Here we concentrate on the halo system of the Milky Way. New data from SDSS/SEGUE has revealed that the halo system comprises at least two components, the inner halo and the outer halo, with demonstrably different characteristics (metallicity distributions, density distributions, kinematics, etc.). In addition to suggesting new ways to examine these data, the inner/outer halo dichotomy has enabled an understanding of at least one long-standing observational result, the increase of the fraction of carbon-enhanced metal-poor (CEMP) stars with decreasing metallicity.