Absolute Proper And Space Motions Of Globular Clusters

Abstract

Absolute proper motions of ten globular clusters with respect to the Hipparcos system are presented. Our new data led to orbits in the Milky Way with smaller apogalactic distances. They are therefore in better agreement with the actual distribution of the globular clusters in the Milky Way. The kinematics of our clusters with respect to the metallicity is discussed. Key words: reference stars; kinematics of globular clusters. 1. INTRODUCTION Globular clusters are important tracers of the chemical evolution and dynamics of the Milky Way. Of special interest are the kinematics of globular clusters, which, however, require accurate absolute proper motions of these objects. We have started a program for the determination of space motions of globular clusters (e.g. Geffert 1987, Brosche et al. 1991) using plates of our refractor in combination with extragalactic calibrated proper motions of stars determined on plates of the Lick astrograph. Several other groups were also active in the deter..