SCYON Abstract

Received on: 25 09 2021

Residual velocities of Small Magellanic Cloud star clusters

Authors:A. E. Piatti 1,2
Affiliations:(1) Instituto Interdisciplinario de Ciencias Básicas (ICB), CONICET UNCUYO, Mendoza, Argentina; (2) Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina
Accepted by: Monthly Notices of the Royal Astronomical Society
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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 ($\Delta$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 ($\Delta$V = 60 km/s). We found that clusters that belong to SMC tidally induced structures have $\Delta$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 $\Delta$V = 64 km/s, slightly above the boundary between bound and kinematically perturbed clusters.


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