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Paper: Field Horizontal-Branch Stars as Tracers of Distances to High Velocity Clouds
Volume: 166, Stromlo Workshop on High-Velocity Clouds
Page: 39
Authors: Beers, Timothy C.
Abstract: Field Horizontal-Branch (FHB) stars in the halo of the Galaxy are luminous, numerous, and have distances which can, in principle, be estimated with accuracies on the order of 10%. As such, they provide nearly ideal probes of the distances to the High Velocity Clouds (assuming they reside) in the halo of the Galaxy. The HK objective-prism survey of Beers and collaborators has identified over 10,000 candidate FHB stars in the apparent magnitude range 11.5 < B < 15.5, which explore distances between 1.5 and 10 kpc from the Sun. The recently-completed Hamburg/ESO prism survey provides candidate FHB stars which reach to apparent magnitudes B ~17.0, exploring distances up to 25 kpc from the Sun. Techniques have been developed which enable accurate estimation of the physical parameters (T_eff, log g, and [Fe/H]) for FHB (and other A-type) stars , a necessary first step in obtaining distance determinations, based on medium-resolution spectroscopy and broadband UBV photometry. What is required presently is a dedicated program of spectroscopy and photometry for FHB/A stars in the directions of prominent High Velocity Clouds.
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