Astronomy and Astrophysics – Astrophysics
Scientific paper
2004-04-16
Mon.Not.Roy.Astron.Soc.352:285,2004
Astronomy and Astrophysics
Astrophysics
16 pages, 15 figures. Accepted for publication in MNRAS
Scientific paper
10.1111/j.1365-2966.2004.07921.x
This is the second in a series of papers presenting a new calculation of the mass of the Galaxy based on radial velocities and distances for a sample of faint 16 < B < 21.3 field blue horizontal-branch (BHB) stars. We present accurate BV CCD photometry and spectra for 142 candidate A-type stars selected from ub_jr photometry of UK Schmidt telescope plates in six high-Galactic-latitude fields. Classification of these candidates produces a sample of 60 BHB stars at distances of 11-52 kpc from the Sun (mean 28 kpc), with heliocentric line-of-sight velocities accurate to 15 km/s, and distance errors < 10%. We provide a summary table listing coordinates and velocities of these stars. The measured dispersion of the radial component of the Galactocentric velocity for this sample is 108+-10 km/s, in agreement with a recent study of the distant halo by Sirko and coworkers. Measurements of the Ca II K line indicate that nearly all the stars are metal-poor with a mean [Fe/H] = -1.8 with dispersion 0.5. Subsequent papers will describe a second survey of BHBs to heliocentric distances 70 < R < 125 kpc and present a new estimate of the mass of the Galaxy.
Clewley Lee
Evans Wyn N.
Hewett Paul C.
Norris John. E.
Warren Stephen J.
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