An Internal Motion Analysis of the Open Cluster M35

The dynamical state of M35 is examined, based upon the proper-motion data of Cudworth and McNamara and Sekiguchi. Mass segregation is present, and its origin is discussed in regard to the mass concentrations observed in the very young cluster NGC 6530. It is suggested that the mass concentrations observed within young objects might be the precursors of similar concentrations observed in intermediate-age clusters. Equipartition of energy among the various mass stars is examined, with the result that the internal rms velocity is found to be essentially independent of stellar mass. This is in agreeemnt with that expected from models incorporating the effects of a galactic tidal field but differs from the relation found by Jones for the Pleiades and Praesepe. The anomalous velocity-mass relation within those clusters is suggested to be caused by a mixture of uneven precision proper motions. The ratio of the M35 radial and tangential velocity dispersions as a function of distance from the cluster center indicates that its orbital motions can be characterized by an isotropic distribution. The anisotropy claimed to exist with the Pleiades is discussed. A possible scenario describing the dynamical evolution of open star clusters is given, along with an explanation for the suspected deficiency of low-mass stars within these objects.