A proper motion survey. I. hyades and UMa moving groups

Abstract

We analyze the results of a proper motion survey in a couple of ESO R 5° X 5° fields, finding evidence for faint (and primarily red) members of the Hyades and UMa moving groups. By the velocity ellipsoid of the Hyades and UMa streams and technique described by Méndez & Ruiz [AJ, 103, 911 (1992) we estimate number densities and nonbiased velocity dispersions for each moving group.Our results suggest that the Hyades moving group extends at least 96 pc in the solid angle covered by our survey, while the UMa moving group shws a decrease in density past 36 pc, indicating that we are looking beyond it. The large tangenital velocity dispersion for both moving groups suggest on the other hand that they are not gravitationaly bound.