Kinematics of young star clusters in the outer northeastern region of the Small Magellanic Cloud

¹ Instituto Interdisciplinario de Ciencias Básicas (ICB), CONICET-UNCuyo, Padre J. Contreras 1300, M5502JMA, Mendoza, Argentina
² Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Godoy Cruz 2290, C1425FQB Buenos Aires, Argentina

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Received: 6 December 2025
Accepted: 23 January 2026

Abstract

It has recently been suggested that the magnitude of the interaction between galaxies could be measured from the level of kinematic disturbance of their outer regions with respect to the innermost ones. In this work, I proved that the outer northeastern region of the Small Magellanic Cloud (SMC), a relatively recent stellar structure with a tidal origin from the interaction with the Large Magellanic Cloud (LMC), is imprinted by a residual velocity pattern. I obtained mean radial velocities (RVs) of star clusters formed in situ from GEMINI GMOS spectra, which, added to derived mean proper motions and heliocentric distances, allowed me to compute their 3D space-velocity components. These space velocities are different from those that the clusters would have if they instead rotated with the galaxy in an orderly fashion; i.e., their residual velocities are larger than the upper limit for an object pertaining to the SMC’s main body rotation disk. The level of kinematic disturbance depends on the SMC rotation disk adopted; galaxy rotation disks traced using relatively old objects are discouraged. The resulting kinematic disturbance arises in younger and older stellar populations, so the epoch of close interaction between both Magellanic Clouds cannot be uncovered on the basis of the kinematics behavior of stellar populations in the outer SMC regions.