The Identification of BHB Stars Using GALEX and other photometry

Abstract

Halo samples that have no kinematic bias have been successfully isolated by photometric observations. We show that the near-UV (NUV) magnitude of the GALEX All-Sky Survey can be used, together with Johnson BV magnitudes in a (NUV-V)_0 vs. (B-V)_0 plot, to distinguish blue horizontal branch (BHB) from other A stars of the same B-V color for 12<V<18. In addition, we use SDSS gr magnitudes in a (NUV - r)_0 vs. (g-r)_0 plot for 14<r<18. The faint limit will be extended by ~3 magnitudes for the GALEX Medium-Deep Survey. Attempts to use NUV in conjunction with 2MASS magnitudes and ROTSE m_r magnitudes did not prove useful. The (NUV - V)_0 vs. (B-V)_0 plot was used to examine BHB star candidates of varying quality near the South Galactic Pole. We conclude that the addition of the GALEX NUV significantly adds to the reliabilty with which these stars can be identified.

arXiv commentAccepted for publication in ApJ Letters

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• Constraints on the Magellanic Clouds' Interaction from the Distribution of OB Stars and the Kinematics of Giants
• The Identification of RR Lyrae and Delta Scuti Stars from Variable GALEX Ultraviolet Sources
• A Stellar Population Synthesis Model for the Study of Ultraviolet Star Counts of the Galaxy
• The BHB stars in the Survey Fields of Rodgers et al. (1993): New Observations and Comparisons with other Recent Surveys
• Multiwavelength study of nearly face-on low surface brightness disk galaxies