THE CENTURY SURVEY GALACTIC HALO PROJECT. III. A COMPLETE 4300 DEG2SURVEY OF BLUE HORIZONTAL BRANCH STARS IN THE METAL-WEAK THICK DISK AND INNER HALO

2007/11/19 by Warren R. Brown, Timothy C. Beers, Ronald Wilhelm +4 · 59 citations
Physics and Astronomy · #Astronomy #Astronomy and Astrophysical Research #Astrophysics #Astrophysics and Star Formation Studies #Galactic halo #Galactic plane #Galaxy #Halo #Horizontal branch #Luminosity #Luminosity function #Metallicity #Physics #Population #Sky #Stars #Stellar, planetary, and galactic studies #Thick disk #astro-ph

paper · pdf · doi:10.1088/0004-6256/135/2/564

published in The Astronomical Journal 135(2), 564-574 (Institute of Physics) · 12 pages in emulateapj format, accepted for publication in February AJ

arxiv created 2007/11/19 · openalex publication_date 2008/01/15 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05

Abstract

We present a complete spectroscopic survey of 2414 2MASS-selected blue horizontal branch (BHB) candidates selected over 4300 deg 2 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.

Citations

• The Field of Streams: Sagittarius and Its Siblings
• The Century Survey Galactic Halo Project. I. Stellar Spectral Analysis
• The Origins and Evolutionary Status of B Stars Found Far from the Galactic Plane. I. Composition and Spectral Features
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• The QUEST RR Lyrae Survey. II. The Halo Overdensities in the First Catalog
• Galactic structure studies from the Beijing-Arizona-Taiwan-Connecticut survey
• The Two Micron All Sky Survey (2MASS)
• A Simplex Method for Function Minimization
• The Second US Naval Observatory CCD Astrograph Catalog (UCAC2)

Cited by

• Targeting Bright Metal-poor Stars in the Disk and Halo Systems of the Galaxy