Residual velocities of Small Magellanic Cloud star clusters

ANDRÉS E. PIATTI

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 2021 vol. 508 p. 3748 - 3753

0035-8711

We analyzed 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-fitted rotating disc of SMC star clusters as a function of the position angle, we computed their residual velocity vectors, and compared their magnitudes (∆V ) with that of a cluster with residual velocity components equal to the velocity dispersions along the three inde- pendent SMC rotating disc axes of motion (∆V = 60 km/s). We found that clusters that belong to SMC tidally induced structures have ∆V > 50 km/s, 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 Mag- ellanic Bridge, the main Magellanic Bridge, the Counter-Bridge and the West halo give support to these findings. NGC 121, the oldest known SMC cluster, does not belong to any SMC tidal feature, and has ∆V = 64 km/s, slightly above the boundary between bound and kinematically perturbed clusters.