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Author Brown, Warren R. ♦ Beers, Timothy C. ♦ Wilhelm, Ronald ♦ Prieto, Carlos Allende ♦ Geller, Margaret J. ♦ Kenyon, Scott J. ♦ Kurtz, Michael J.
Source CiteSeerX
Content type Text
File Format PDF
Subject Domain (in DDC) Computer science, information & general works ♦ Data processing & computer science
Subject Keyword Bhb Star ♦ Mean Metallicity ♦ Thick-disk Bhb Star ♦ Hot Bhb Star ♦ Thick Disk Bhb ♦ Luminosity Function ♦ Density Scale Height ♦ Field Bhb Star ♦ Relative Normalization ♦ Metal-weak Thick Disk Population ♦ Galactic Plane ♦ Inner-halo Population ♦ Rotation Velocity Gradient ♦ Mean Galactic Rotation ♦ 2mass-selected Blue Horizontal Branch ♦ Kpc Trace ♦ Complete Spectroscopic Survey
Abstract 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.
Educational Role Student ♦ Teacher
Age Range above 22 year
Educational Use Research
Education Level UG and PG ♦ Career/Technical Study