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

Warren R. Brown, Timothy C. Beers, Ronald Wilhelm, Carlos Allende Prieto, Margaret J. Geller, Scott J. Kenyon, Michael J. Kurtz

Research output: Contribution to journalArticlepeer-review

47 Scopus citations

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.

Original languageEnglish
Pages (from-to)564-574
Number of pages11
JournalAstronomical Journal
Volume135
Issue number2
DOIs
StatePublished - Feb 1 2008

Keywords

  • Galaxy: halo
  • Galaxy: stellar content
  • Stars: early type
  • Stars: horizontal-branch

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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