EDP Sciences
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Volume 431, Number 1, February III 2005
Page(s) 143 - 148
Section Galactic structure, stellar clusters and populations
DOI http://dx.doi.org/10.1051/0004-6361:20041830

A&A 431, 143-148 (2005)
DOI: 10.1051/0004-6361:20041830

The stellar content of the Hamburg/ESO survey

III. Field horizontal-branch stars in the Galaxy
N. Christlieb1, T. C. Beers2, C. Thom3, R. Wilhelm4, S. Rossi5, C. Flynn6, L. Wisotzki7 and D. Reimers1

1  Hamburger Sternwarte, Universität Hamburg, Gojenbergsweg 112, 21029 Hamburg, Germany
    e-mail: [nchristlieb;dreimers]@hs.uni-hamburg.de
2  Department of Physics & Astronomy and JINA: Joint Institute for Nuclear Astrophysics, Michigan State University, East Lansing, MI 48824, USA
    e-mail: beers@pa.msu.edu
3  Centre for Astrophysics and Supercomputing, Swinburne University of Technology, Hawthorn, VIC 3122, Australia
    e-mail: cthom@astro.swin.edu.au
4  Department of Physics, Texas Tech University, Lubbock, TX 79409, USA
    e-mail: ron.wilhelm@ttu.edu
5  Departamento de Astronomia Instituto de Astronomia, Geofísica e Ciências Atmosféricas, Universidade de São Paulo, 05508-900 São Paulo SP, Brazil
    e-mail: rossi@astro.iag.usp.br
6  Tuorla Observatory, University of Turku, Väisäläntie 20, 21500 Piikkiö, Finland
    e-mail: cflynn@utu.fi
7  Astrophysikalisches Institut Potsdam, An der Sternwarte 16, 14482 Potsdam, Germany
    e-mail: lutz@aip.de

(Received 11 August 2004 / Accepted 20 October 2004 )

We present a sample of 8321 candidate Field Horizontal-Branch (FHB) stars selected by automatic spectral classification in the digital data base of the Hamburg/ESO objective-prism survey. The stars are distributed over 8225 square degrees of the southern sky, at $\vert b\vert \gtrsim 30\,\deg$. The average distance of the sample, assuming that they are all FHB stars, is 9.8 kpc, and distances of up to $\sim $30 kpc are reached. Moderate-resolution spectroscopic follow-up observations and UBV photometry of 125 test sample stars demonstrate that the contamination of the full candidate sample with main-sequence A-type stars is <16%, while it would be up to 50% in a flux-limited sample at high galactic latitudes. Hence more than $\sim $ 6800 of our FHB candidates are expected to be genuine FHB stars. The candidates are being used as distance probes for high-velocity clouds and for studies of the structure and kinematics of the Galactic halo.

Key words: stars: horizontal-branch -- Galaxy: halo -- Galaxy: kinematics and dynamics -- surveys -- methods: statistical

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