On the common origin of the AB Dor moving group and the Pleiades cluster

Abstract

AB Dor is the nearest identified moving group. As with other such groups, the age is important for understanding of several key questions. It is important, for example, in establishing the origin of the group and also in comparative studies of the properties of planetary systems, eventually surrounding some of the AB Dor group members, with those existing in other groups. For AB Dor two rather different estimates for its age have been proposed: a first one, of the order of 50 Myr, by Zuckerman and coworkers from a comparison with Tucana/Horologium moving group and a second one of about 100-125 Myr by Luhman and coworkers from color-magnitude diagrams (CMD). Using this last value and the closeness in velocity space of AB Dor and the Pleiades galactic cluster, Luhman and coworkers suggested coevality for these systems. Because strictly speaking such a closeness does not still guarantee coevality, here we address this problem by computing and comparing the full 3D orbits of AB Dor, Pleiades, alpha Persei and IC 2602. The latter two open clusters have estimated ages of about 85-90 Myr and 50 Myr. The resulting age 119 $\pm$ 20 Myr is consistent with AB Dor and Pleiades being coeval. Our solution and the scenario of open cluster formation proposed by Kroupa and collaborators suggest that the AB Dor moving group may be identified with the expanding subpopulation (Group I) present in this scenario. We also discuss other related aspects as iron and lithium abundances, eventual stellar mass segregation during the formation of the systems and possible fraction of debris discs in AB Dor group.