The Effect of Drag from the Galactic Hot Halo on the Magellanic Stream and Leading Arm

TL;DR

This study investigates how drag from the Galactic hot halo influences the formation and observed properties of the Magellanic Stream and Leading Arm, improving agreement with observations through numerical simulations.

Contribution

The paper introduces the inclusion of drag effects in tidal formation models of the Magellanic Stream and Leading Arm, offering new insights into their dynamics and structure.

Findings

Drag improves model alignment with observed kinematics.

Drag reproduces the Magellanic Stream's column density gradient.

Drag enhances the formation of the MS bifurcation.

Abstract

We study the effect of drag induced by the Galactic hot halo on the two neutral hydrogen (HI) cloud complexes associated with the Large and Small Magellanic Clouds: the Magellanic Stream (MS) and the Leading Arm (LA). In particular, we adopt the numerical models of previous studies and re-simulate the tidal formation of the MS and LA with the inclusion of a drag term. We find that the drag has three effects which, although model-dependent, may bring the tidal formation scenario into better agreement with observations: correcting the LA kinematics, reproducing the MS column density gradient, and enhancing the formation of MS bifurcation. We furthermore propose a two-stage mechanism by which the bifurcation forms. In general, the inclusion of drag has a variety of both positive and negative effects on the global properties of the MS and LA, including their on-sky positions, kinematics, radial distances, and column densities. We also provide an argument which suggests that ram pressure stripping and tidal stripping are mutually exclusive candidates for the formation of the MS and LA.