Radial velocities in Be 44, Be 81, and NGC 6802

These clusters are of intermediate age (1-3Gyr), located within the solar Galactocentric radius, and have no previous radial velocity measurements. We find mean radial velocities of -9.6{+/-}3.0km/s, 48.1{+/-}2.0km/s, and 12.4{+/-}2.8km/s for Be 44, Be 81, and NGC 6802, respectively.

We present an analysis of radial velocities of 134 open clusters of a wide range of ages using data obtained in this study and the literature. Assuming the system of clusters rotates about the Galactic center with a constant velocity, we find older clusters exhibit a slower rotation and larger line-of-sight (LOS) velocity dispersion than younger clusters. The gradual decrease in rotational velocity of the cluster system with age is accompanied by a smooth increase in LOS velocity dispersion, which we interpret as the effect of heating on the open cluster system over time.