# Two kinematically distinct old globular cluster populations in the Large Magellanic Cloud

## TL;DR

This study uses Gaia DR2 data to identify two distinct kinematic populations of old globular clusters in the LMC, revealing differences in their motion and spatial distribution, suggesting a common formation process.

## Contribution

It uncovers two kinematically distinct old globular cluster populations in the LMC using Gaia data, linking their dynamics to possible simultaneous halo and disc formation.

## Key findings

- Two kinematic groups with different velocities and spatial distributions.
- Clusters with smaller vertical velocities are part of the LMC disc.
- Clusters with larger velocities form a spherical component.

## Abstract

We report results of proper motions of 15 known Large Magellanic Cloud (LMC) old globular clusters (GCs) derived from the Gaia DR2 data sets. When these mean proper motions are gathered with existent radial velocity measurements to compose the GCs' velocity vectors, we found that the projection of the velocity vectors onto the LMC plane and those perpendicular to it tell us about two distinct kinematic GC populations. Such a distinction becomes clear if the GCs are split at a perpendicular velocity of 10 km/s (absolute value). The two different kinematic groups also exhibit different spatial distributions. Those with smaller vertical velocities are part of the LMC disc, while those with larger values are closely distributed like a spherical component. Since GCs in both kinematic-structural components share similar ages and metallicities, we speculate with the possibility that their origins could have occurred through a fast collapse that formed halo and disc concurrently.