In addition to optical photometry of unprecedented quality , the Sloan Digital Sky Survey ( SDSS ) is also producing a massive spectroscopic database .
We discuss determination of stellar parameters , such as effective temperature , gravity and metallicity from SDSS spectra , describe correlations between kinematics and metallicity , and study their variation as a function of the position in the Galaxy .
We show that stellar parameter estimates by Beers et al .
show a good correlation with the position of a star in the g - r vs . u - g color-color diagram , thereby demonstrating their robustness as well as a potential for photometric parameter estimation methods .
Using Beers et al .
parameters , we find that the metallicity distribution of the Milky Way stars at a few kpc from the galactic plane is bimodal with a local minimum at [ Z / Z _ { \odot } ] \sim - 1.3 .
The median metallicity for the low-metallicity [ Z / Z _ { \odot } ] < -1.3 subsample is nearly independent of Galactic cylindrical coordinates R and z , while it decreases with z for the high-metallicity [ Z / Z _ { \odot } ] > -1.3 sample .
We also find that the low-metallicity sample has \sim 2.5 times larger velocity dispersion and that it does not rotate ( at the \sim 10 km/s level ) , while the rotational velocity of the high-metallicity sample decreases smoothly with the height above the galactic plane .