Kinematics of K giants in the outer galactic halo.

The authors describe a technique for finding field K giants in the outer galactic halo, 10 - 40 kpc from the galactic center. A sample of over 150 distant halo giants was located from an automated objective-prism survey of three high galactic latitude fields, each of 20 square degrees. Radial velocities of these giants show that (1) the outer halo is at most slowly rotating and (2) the line-of-sight velocity dispersion in our two best studied fields is approximately constant with distance from the Sun. The data on the run of velocity dispersion with distance in the halo fits well to a simple kinematical model in which the components of the velocity dispersion in cylindrical polar coordinates (with origin at the galactic center) remain constant everywhere, and equal to the anisotropic values seen in the solar neighborhood.