SEGUE: A SPECTROSCOPIC SURVEY OF 240,000 STARS WITH<i>g</i>= 14-20

The Sloan Extension for Galactic Understanding and Exploration (SEGUE) Survey obtained ≈240,000 moderateresolution (R ~ 1800) spectra from 3900 Å to 9000 Å of fainter Milky Way stars (14.0 &lt; g &lt; 20.3) of a wide&#13;\nvariety of spectral types, both main-sequence and evolved objects, with the goal of studying the kinematics and&#13;\npopulations of our Galaxy and its halo. The spectra are clustered in 212 regions spaced over three quarters of the&#13;\nsky. Radial velocity accuracies for stars are σ(RV) ~ 4 km s^(−1) at g &lt; 18, degrading to σ(RV) ~ 15 km s^(−1)&#13;\nat g ~ 20. For stars with signal-to-noise ratio &gt;10 per resolution element, stellar atmospheric parameters are estimated, including metallicity, surface gravity, and effective temperature. SEGUE obtained 3500 deg^2 of additional&#13;\nugriz imaging (primarily at low Galactic latitudes) providing precise multicolor photometry (σ(g, r, i) ~ 2%),&#13;\n(σ(u, z) ~ 3%) and astrometry (≈0".1) for spectroscopic target selection. The stellar spectra, imaging data, and&#13;\nderived parameter catalogs for this survey are publicly available as part of Sloan Digital Sky Survey Data Release 7.