Kinematics of young star clusters in the outer north-eastern region of the Small Magellanic Cloud

TL;DR

This study reveals that the outer north-eastern region of the Small Magellanic Cloud exhibits residual velocity patterns indicating kinematic disturbance from galaxy interactions, analyzed through star cluster velocities and proper motions.

Contribution

It provides the first detailed 3D kinematic analysis of star clusters in the outer SMC, demonstrating residual velocities indicative of tidal disturbance from galaxy interactions.

Findings

Outer SMC shows residual velocities larger than expected from rotation.

Kinematic disturbance affects both young and old stellar populations.

Interaction epoch cannot be determined solely from outer SMC stellar kinematics.

Abstract

It has been suggested since recent time 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. Here, I proved that the outer north-eastern region of the Small Magellanic Cloud (SMC), a relatively recent stellar structure with a tidal origin from the interaction with the Large Magellanic Cloud, is imprinted by a residual velocity pattern. I obtained from GEMINI GMOS spectra mean radial velocities of star clusters formed in situ, which added to derived mean proper motions and heliocentric distances, allowed to compute their 3D space velocity components. These space velocities differentiate from those that the clusters would have if they instead orderly rotated with the galaxy, i.e., their residual velocities are larger than the upper limit for an object pertaining to the SMC 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 that the epoch of close interaction between both Magellanic Clouds cannot be uncovered on the basis of the kinematics behavior of stellar populations populating the outer SMC