SDSS Spectroscopic Survey of Stars

Résumé du livre

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-?] -1.3. The median metallicity for the low-metallicity [Z/Z-?] -1.3 sample. We also find that the low-metallicity sample has 2.5 times larger velocity dispersion and that it does not rotate (at the 10 km/s level), while the rotational velocity of the high-metallicity sample decreases smoothly with the height above the galactic plane.