2021MNRAS.508.3748P

We analysed the largest Small Magellanic Cloud (SMC) cluster sample (32) with proper motions and radial velocity measurements, from which we obtained their space velocity components. By adopting as a reference, the recent best-fitting rotating disc of SMC star clusters as a function of the position angle, we computed their residual velocity vectors, and compared their magnitudes (ΔV) with that of a cluster with residual velocity components equal to the velocity dispersions along the three independent SMC rotating disc axes of motion (ΔV = 60 km s^–1). We found that clusters that belong to SMC tidally induced structures have ΔV > 50 km s^–1, which suggests that space velocities of clusters in the process of escaping the rotating disc kinematics are measurably different. Studied clusters pertaining to a northern branch of the Magellanic Bridge, the main Magellanic Bridge, the Counter-Bridge, and the West Halo give support these findings. NGC 121, the oldest known SMC cluster, does not belong to any SMC tidal feature, and has ΔV = 64 km s^–1, slightly above the boundary between bound and kinematically perturbed clusters.