The stellar content of the Hamburg / ESO survey ⋆ III . Field horizontal - branch stars in the Galaxy

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 |b| 30 deg. The average distance of the sample, assuming that they are all FHB stars, is 9.8 kpc, and distances of up to ∼ 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 ∼ 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.