Modeling the recent interactions between the Magellanic Clouds and Milky Way

TL;DR

This study models the past 2.5 billion years of interactions between the Milky Way and its Magellanic Cloud satellites using N-body simulations and genetic algorithms, revealing key interaction events and their effects on galaxy structures.

Contribution

It introduces a novel combination of genetic algorithms with N-body simulations to accurately reconstruct the orbital history of the Magellanic Clouds.

Findings

Identified two major close interactions 940 Myr and 140 Myr ago.

Reproduced observed features like the LMC disc warp and SMC tidal expansion.

Showed the recent interaction caused global ripples in the LMC disc.

Abstract

The Large and Small Magellanic Clouds (LMC and SMC, respectively) are the largest satellite galaxies of the Milky Way (MW) and their interactions with each other have given rise to multiple stellar substructures in their periphery as well as the gaseous Magellanic Stream. To better understand the origin of the stellar substructures and constrain their past orbit, we model the past 2.5 Gyr of the interactions between the MW and the LMC and SMC using N-body simulations. Due to the strong interactions, analytical orbit integrations are insufficient to analyze the past galaxy orbits accurately. Therefore, we use a genetic algorithm in combination with N-body simulations to determine the LMC and SMC initial positions and velocities 2.5 Gyr ago that result in the Magellanic Clouds (MCs) arriving near their observed locations and velocities at the current time. After running ~8,000 simulations, our best matching model includes two close interactions between the MCs (940 Myr and 140 Myr ago) and reproduces some observed features of the MCs, including the LMC disc warp, a ring-shaped overdensity in the LMC, the tidal expansion of the SMC, and a greater distance dispersion on the eastern side of the SMC. The LMC disc warp is caused by the most recent interaction with the SMC, which occurred ~140 Myr before the present. The interaction causes global ripples in the LMC disc with a mean amplitude of 1.3 kpc.