Key points are not available for this paper at this time.
The authors present the metallicity distribution perpendicular to the Galactic plane, to distances of order 2 kpc. This has been derived by comparison of new photometry and existing spectroscopic samples of stars in situ and local samples of kinematically selected stars. The metallicity distribution the authors find is best characterized by a sum of three independent components, each with a well-defined mean abundance and little or no gradient in this mean, but with very different spatial density distributions. These components are identified as the Galactic thin disk, the Galactic thick disk, and the Galactic extreme spheroid. The relative number of stars in the solar vicinity in each of these populations are very approximately 0.2:1.0:0.02:0.001 for the young disk, the old disk, thick disk, and spheroid, respectively. The thick disk is shown to have kinematic properties intermediate between the thin disk and spheroid. The consequences of these results for theories of Galaxy formation are briefly discussed.
Gilmore et al. (Tue,) studied this question.