A comprehensive kinematic model of the LMC disk from star clusters and field stars using Gaia DR3: Tracing the disk characteristics, rotation, bar, and the outliers

TL;DR

This study presents a detailed 2D kinematic model of the LMC disk using Gaia DR3 data, revealing differences between star clusters and field stars, and evidence of perturbations from interactions with the SMC.

Contribution

First comprehensive 2D kinematic analysis of the LMC disk using star clusters, highlighting variations with age and evidence of recent dynamical disturbances.

Findings

Clusters and field stars have different kinematic centers and disk parameters.

Large residual motions suggest perturbations from the bar and spiral arms.

Detected non-circular motions likely caused by recent LMC-SMC collision.

Abstract

The internal kinematics of the Large Magellanic Cloud (LMC) disk have been modeled by several studies using different tracers with varying coverage, resulting in a range of parameters. Here, we modeled the LMC disk using 1705 star clusters and field stars, based on a robust Markov Chain Monte Carlo (MCMC) method, using the Gaia DR3 data. The dependency of model parameters on the age, coverage, and strength of the clusters are also presented. This is the first comprehensive 2D kinematic study using star clusters. Red clump (RC) stars and young main-sequence stars are also modeled for comparison. The clusters and field stars are found to have distinctly different kinematic centers, disk inclination, position angle of the line of nodes, and scale radius. We also note a significant radial variation of the disk parameters. Clusters and young stars are found to have a large residual proper motion and a relatively large velocity dispersion when compared to the RC field population, which could be due to perturbation from the bar and spiral arms. We traced the presence of large residual proper motion and non-circular motion among clusters likely to be due to the bar and detected a decrease in the scale radius as a result of the possible evolution of the bar. The kinematically deviant clusters point to a spatio-temporal disturbance in the LMC disk, matching with the expected impact factor and time of the recent collision between the LMC and the Small Magellanic Cloud.