The VMC survey -- XLV. Proper motion of the outer LMC and the impact of the SMC

TL;DR

This study uses stellar proper motions from VISTA and Gaia data, combined with machine learning, to analyze the outer LMC's kinematics and the impact of the SMC, revealing signs of SMC debris and altered rotation.

Contribution

Introduces a new machine learning method for star classification and provides detailed kinematic analysis of the LMC's outer regions influenced by the SMC.

Findings

Detection of SMC debris in the LMC's outer regions.

Slower rotation in the southeast of the LMC.

Evidence of stars moving opposite to expected rotation due to SMC interaction.

Abstract

The Large Magellanic Cloud (LMC) is the most luminous satellite galaxy of the Milky Way and owing to its companion, the Small Magellanic Cloud (SMC), represents an excellent laboratory to study the interaction of dwarf galaxies. The aim of this study is to investigate the kinematics of the outer regions of the LMC by using stellar proper motions to understand the impact of interactions, e.g. with the SMC about 250 Myr ago. {We calculate proper motions using multi-epoch $K_\mathrm{s}$-band images from the VISTA survey of the Magellanic Clouds system (VMC). Observations span a time baseline of 2$-$5 yr. We combine the VMC data with data from the Gaia early Data Release 3 and introduce a new method to distinguish between Magellanic and Milky Way stars based on a machine learning algorithm. This new technique enables a larger and cleaner sample selection of fainter sources as it reaches below the red clump of the LMC. We investigate the impact of the SMC on the rotational field of the LMC and find hints of stripped SMC debris. The south east region of the LMC shows a slow rotational speed compared to the overall rotation. $N$-body simulations suggest that this could be caused by a fraction of stripped SMC stars, located in that particular region, that move opposite to the expected rotation.