The Tidal Origin of the Magellanic Stream and the Possibility of a Stellar Counterpart

TL;DR

This paper presents an N-body model demonstrating that the Magellanic Stream originated from tidal interactions between the Magellanic Clouds and the Milky Way, revealing new insights into their orbital history and stellar structures.

Contribution

The study introduces a detailed N-body simulation showing the tidal origin of the Magellanic Stream and explores the stellar counterpart, based on recent proper motion data and orbital analysis.

Findings

The Magellanic Stream was formed by tidal forces during a close encounter 2 Gyr ago.

The model reproduces the bifurcation of the MS into two filaments.

An extended stellar spheroid of the SMC may produce a stellar stream similar to the gaseous MS.

Abstract

We present an N-body model that reproduces the morphology and kinematics of the Magellanic Stream (MS), a vast neutral hydrogen (HI) structure that trails behind the Large and Small Magellanic Clouds (LMC and SMC, respectively) in their orbit about the Milky Way. After investigating 8 million possible orbits consistent with the latest proper motions, we adopt an orbital history in which the LMC and SMC have only recently become a strongly interacting binary pair. We find that their first close encounter 2 Gyr ago provides the necessary tidal forces to disrupt the disk of the SMC and thereby create the MS. The model also reproduces the on-sky bifurcation of the two filaments of the MS, and we suggest that a bound association with the Milky Way is required to reproduce the bifurcation. Additional HI structures are created during the tidal evolution of the SMC disk, including the Magellanic Bridge, the "Counter-Bridge", and two branches of leading material. Insights into the chemical evolution of the LMC are also provided, as a substantial fraction of the material stripped away from the SMC is engulfed by the LMC. Lastly we compare three different N-body realizations of the stellar component of the SMC, which we model as a pressure-supported spheroid motivated by recent kinematical observations. We find that an extended spheroid is better able to explain the stellar periphery of the SMC, and the tidal evolution of the spheroid may imply the existence of a stellar stream akin to the gaseous MS.