Kinematics of Metal-poor Stars in the Galaxy. III. Formation of the Stellar Halo and Thick Disk as Revealed from a Large Sample of Nonkinematically Selected Stars

(Abbreviated) We present a detailed analysis of the space motions of 1203solar-neighborhood stars with metal abundances [Fe/H] <= -0.6, on the basis ofa recently revised and supplemented catalog of metal-poor stars selectedwithout kinematic bias (Beers et al. 2000). This sample, having availableproper motions, radial velocities, and distance estimates for stars with a widerange of metal abundances, is by far the largest such catalog to be assembledto date. Unlike essentially all previous kinematically selected catalogs, themetal-poor stars in our sample exhibit a diverse distribution of orbitaleccentricities, e, with no apparent correlation between [Fe/H] and e. Thisdemonstrates, clearly and convincingly, that the evidence offered by Eggen,Lynden-Bell, and Sandage (1962) for a rapid collapse of the Galaxy, an apparentcorrelation between the orbital eccentricity of halo stars with metallicity, isbasically the result of their proper-motion selection bias. However, even inour non-kinematically selected sample, we have identified a small concentrationof high-e stars at [Fe/H] = -1.7, which may originate, in part, from infallinggas during the early formation of the Galaxy. The implications of our resultsfor the formation of the Galaxy are also discussed, in particular in thecontext of the currently favored CDM theory of hierarchical galaxy formation.