Lessons from the Magellanic System and its modeling

TL;DR

This paper evaluates models explaining the Magellanic Stream, finding that a 'ram-pressure plus collision' model better reproduces observed properties and predicts recent features, suggesting a low mass for the Magellanic Clouds.

Contribution

The study demonstrates that the 'ram-pressure plus collision' model effectively explains the Magellanic Stream's properties and recent observations, outperforming tidal models.

Findings

The 'ram-pressure plus collision' model reproduces the Stream's complex features.

Tidal models cannot account for the observed filaments and gas mass.

A low mass for the Magellanic Clouds is favored for Stream formation.

Abstract

The prominent Magellanic Stream that dominates the HI sky provides a tantalizing number of observations that potentially constrains the Magellanic Clouds and the Milky Way outskirts. Here we show that the 'ram-pressure plus collision' model naturally explain these properties, and is able to predict some of the most recent observations made after the model was made. These include the complexity of the stellar populations in the Magellanic Bridge, for which kinematics, ages, and distances are well measured, and the North Tidal Arm, for which the model predicts its formation from the Milky Way tidal forces. It appears that this over-constrained model provides a good path to investigate the Stream properties. This contrasts with tidal models that reproduce only half of the Stream's main properties, in particular a tidal tail cannot reproduce the observed inter-twisted filaments, and its gas content is not sufficiently massive to provide the large amount of HI and HII gas associated to the Stream. Despite the efforts made to reproduce the large amounts of gas brought by the Clouds, it seems that no viable solution for the tidal model could be foreseen. Since the 'ram-pressure plus collision' model has not succeeded for a Large Magellanic Cloud mass above 2 $\times10^{10}$ $M_{\odot}$, we conjecture that a low mass is required to form the Stream.