TY - JOUR
T1 - 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
AU - Brown, Warren R.
AU - Beers, Timothy C.
AU - Wilhelm, Ronald
AU - Prieto, Carlos Allende
AU - Geller, Margaret J.
AU - Kenyon, Scott J.
AU - Kurtz, Michael J.
PY - 2008/2/1
Y1 - 2008/2/1
N2 - 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 dvrot/d|Z| = -28 3.4 km s-1 in the region |Z| < 6 kpc, and a density scale height of hZ = 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.
AB - 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 dvrot/d|Z| = -28 3.4 km s-1 in the region |Z| < 6 kpc, and a density scale height of hZ = 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.
KW - Galaxy: halo
KW - Galaxy: stellar content
KW - Stars: early type
KW - Stars: horizontal-branch
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U2 - 10.1088/0004-6256/135/2/564
DO - 10.1088/0004-6256/135/2/564
M3 - Article
AN - SCOPUS:46249084265
SN - 0004-6256
VL - 135
SP - 564
EP - 574
JO - Astronomical Journal
JF - Astronomical Journal
IS - 2
ER -