Kinematic complexity around NGC$\,$419: resolving the proper motion of the cluster, the Small Magellanic Cloud and the Magellanic Bridge

TL;DR

This study uses high-precision Hubble Space Telescope proper motions to disentangle the complex kinematics of stars around NGC 419, revealing distinct motions of the cluster, Small Magellanic Cloud, and Magellanic Bridge, enabling detailed dynamical analysis.

Contribution

First high-precision proper motion measurements resolve the kinematic complexity of stellar populations near NGC 419, separating cluster, SMC, and Magellanic Bridge motions for the first time.

Findings

Resolved the proper motions of NGC 419, SMC, and Magellanic Bridge stars.

Separated the kinematic components allowing for decontaminated color-magnitude diagrams.

Measured the absolute proper motions of the three components.

Abstract

We present $\it{Hubble}$ $\it{Space}$ $\it{Telescope}$ proper motions in the direction of the star cluster NGC$\,$419 in the Small Magellanic Cloud. Because of the high precision of our measurements, for the first time it is possible to resolve the complex kinematics of the stellar populations located in the field, even along the tangential direction. In fact, the proper motions we measured allow us to separate cluster stars, which move on average with ($\mu_{\alpha}\cos\delta^{\rm NGC\,419}, \mu_{\delta}^{\rm NGC\,419}$) = ($+0.878\pm0.055$, $-1.246\pm0.048$) mas yr$^{-1}$, from those of the Small Magellanic Cloud and those belonging to a third kinematic feature that we recognise as part of the Magellanic Bridge. Resolving such a kinematic complexity enables the construction of decontaminated colour-magnitude diagrams, as well as the measurement of the absolute proper motion of the three separate components. Our study therefore sets the first steps towards the possibility of dynamically investigating the Magellanic system by exploiting the resolved kinematics of its stellar clusters.