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[21.10] Horizontal-Branch Stars as Probes of Structure in the Halo of the Milky Way

B. Marsteller, T.C. Beers (Michigan State University), N. Christlieb (Hamburger Sternwarte, Germany), C. Thom (Swinburn Univ., Australia)

In the past decade, increasing larger samples of field stars in the Milky Way have been used to constrain the shape and dynamics of the halo and thick-disk populations, to estimate the mass of the Milky Way, and to search for the presence of coherent streams of stars likely arising from shredded dwarf galaxies such as Sagittarius and Canis Major. Horizontal-branch stars, owing to their large numbers, intrinsic luminosity, and distinctive spectroscopic appearance, are proving to be particularly useful probes.

Here we report on a search for the presence of structure based on a new sample of 8321 candidate horizontal-branch stars selected from the Hamburg/ESO (HES) objective-prism survey (see Christlieb et al. 2004). This sample has been ``cleaned'' from potentially large contamination by higher gravity A-type stars, such as halo blue stragglers, through the application of an automatic classification procedure based on the flux-calibrated HES prism plates. The mean distance to the candidate horizontal-branch stars in this catalog is 10 kpc from the Sun, but it includes stars as distant as 30 kpc.

This work received partial funding support from grant PHY 02-16783 Physics Frontier Centers/JINA: Joint Institute for Nuclear Astrophysics, awarded by the US National Science Foundation.

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Bulletin of the American Astronomical Society, 36 5
© 2004. The American Astronomical Society.