The Similarity of the Halo Field K Giant Population by the Globular Cluster System of our Galaxy

Extract

Line-of-sight velocities and improved metal abundance estimates are available for a representative sample of 58 giants located by an objective prism survey (Ratnatunga and Freeman 1985), in a 20 square degree field near SA 127 (1 = 272, b = +39). These in-situ K-giants of the outer regions of our galactic halo give a direct comparison of the field population with the globular cluster system. Fig. 1 illustrates the distribution of line-of-sight velocity with abundance for the sample of giant stars in SA 127. The mean and dispersion of the sample appears to be discontinuous at [FeH] ~ −0.8. Fig. 2 shows the distribution of [Fe/H] with distance from the Sun for the same stars. The metal stronger giants (filled symbols) represent a population of stars up to 6 kpc above the plane of the disk and have a velocity dispersion of about 50 km/s. In contrast, the metal weaker giants have a typical halo dispersion of about 120 km/s.