How Common can the Origin of Clusters Cha I, Cha II, ϵ Cha and η Cha be?

Abstract

The trajectories of the groupings η Cha, ϵ Cha and Cha I, Cha II, constructed backward in time, have been studied. We concluded that the hypothesis about the joint formation of all four of these clusters from one molecular cloud cannot be completely excluded. However, 10–15 Myr ago, all these four clusters were located at approximately the same height above the plane of the Galaxy. Thus, the gas-dust clouds from which all these four clusters were formed were located on one broad front. It is possible that the appearance of the Cha I, Cha II, ϵ Cha and η Cha clusters may be associated with the impact on such a front of shock waves formed after supernova explosions in the Scorpius–Centaurus association. New estimates of the kinematic ages of the clusters Cha I and Cha II are obtained as 0.12 ± 0.19 and 0.05 ± 0.15, respectively. It is shown that the minimum size of the Cha I-north and Cha I-south clusters corresponded to the time of 0.55 ± 0.24 Myr and 0.04 ± 0.18 Myr ago, respectively, and approximately 1.5 Myr ago the distance between the trajectories of these two groupings was minimal.