Globular clusters and the potential well of the Galaxy

The structure and dynamics of the Galactic globular-cluster (GC) system are studied, using a sample of 68 objects, at apparent Galactocentric distances of from 2 to 40 kpc, for which measured velocities and reliable distances are available. Constant-eccentricity and Eddington-like models are discussed. It is found that GC velocities are not strongly biased in the radial direction in the region within the solar circle, and that the data are well characterized by an isotropic velocity distribution. The low velocity dispersion of the GC system makes it probable that the characteristic Galactic rotation velocity at solar radius is less than 220 km/sec, while the increase in dispersion with radius demands a flat or rising 'effective' Galactic-rotation curve from 2 to 30 kpc.