The century survey galactic halo project. III. A complete 4300 DEG ² survey of blue horizontal branch stars in the metal-weak thick disk and inner halo

We present a complete spectroscopic survey of 2414 2MASS-selected blue horizontal branch (BHB) candidates selected over 4300 deg² of the sky. We identify 655 BHB stars in this non-kinematically selected sample. We calculate the luminosity function of field BHB stars, and find evidence for very few hot BHB stars in the field. The BHB stars located at a distance from the Galactic plane |Z| < 4 kpc trace what is clearly a metal-weak thick disk population, with a mean metallicity of [Fe/H] = -1.7, a rotation velocity gradient of dv_rot/d|Z| = -28 3.4 km s^-1 in the region |Z| < 6 kpc, and a density scale height of h_Z = 1.26 0.1 kpc. The BHB stars located at 5 < |Z| < 9 kpc are a predominantly inner-halo population, with a mean metallicity of [Fe/H] = -2.0 and a mean Galactic rotation of -4 31 km s^-1. We infer the density of halo and thick disk BHB stars is 104 37 kpc^-3 near the Sun, and the relative normalization of halo to thick-disk BHB stars is 4 1% near the Sun.