Abstract

Recent evidence that the Galactic halo have been formed by accretion of sub-galactic fragments comes from the analysis of Carollo et al. (2007, 2010), based on a large sample of calibration stars from the Sloan Digital Sky Survey (SDSS) DR5 and SDSS SEGUE DR7 . Carollo et al. argued for the existence of at least a two-component halo. In their view, the Galactic halo comprises two broadly overlapping structural components, an inner and an outer halo. These components exhibit different spatial density profiles, stellar orbits, velocity ellipsoids and stellar metallicities. I will present the general properties of the two stellar halo components, and evidence that they may have experienced a distinct chemical enrichment at early epochs of the Galaxy’s formation, through an analysis of the Carbon-Enhanced Metal-Poor (CEMP) stars in the inner- and outer-halo populations.