GLOBAL KINEMATICS OF THE GLOBULAR-CLUSTER M15

We present velocities for 230 stars in the outer parts of the globular cluster M15 measured with the Hydra multifiber spectrograph on the 3. 5 m WIYN telescope. A new Bayesian technique is used for analyzing the data. The mean velocity of the cluster is -106.9 +/- 0.3 km s(-1). Ro tation with an amplitude of 1.5 +/- 0.4 km s(-1) and a position angle of 125 degrees +/- 19 degrees is observed, and a model including rotat ion is marginally favored over one without rotation. The velocity disp ersion decreases from the center out to about 7' and then appears to i ncrease slightly. This behavior is strikingly different from the conti nued decline of velocity dispersion with increasing radius that is exp ected in an isolated cluster. We interpret this as an indication of he ating of the outer part of M15 by the Galactic tidal field.