CHEMICAL ABUNDANCES OF THE MILKY WAY THICK DISK AND STELLAR HALO. I. IMPLICATIONS OF α/Fe FOR STAR FORMATION HISTORIES IN THEIR PROGENITORS

We present the abundance analysis of 97 nearby metal-poor (-3. 3-2. These results favor the scenarios that the MW thick disk formed through rapid chemical enrichment primarily through Type II supernovae of massive stars, while the stellar halo has formed at least in part via accretion of progenitor stellar systems having been chemically enriched with different timescales.