The small-scale Structure of the Magellanic Stream as a Foundation for Galaxy Evolution

TL;DR

This paper investigates the small-scale structure and evolution of the Magellanic Stream, highlighting its complex gas dynamics, interactions with the Milky Way, and implications for galaxy evolution and star formation.

Contribution

It provides new insights into the small-scale structures and kinematics of the Magellanic Stream through recent HI observations and hydrodynamic analysis.

Findings

The northern MS has a larger spatial extent than previously known.

Small-scale structures and turbulence influence the survival of cool gas in the MS.

The MS shows little evidence of star formation despite abundant cool gas.

Abstract

The Magellanic Stream (MS) is the nearest example of a gaseous trail formed by interacting galaxies. While the substantial gas masses in these kinds of circumgalactic structures are postulated to represent important sources of fuel for future star formation, the mechanisms whereby this material might be accreted back into galaxies remain unclear. Recent neutral hydrogen (HI) observations have demonstrated that the northern portion of the MS, which probably has been interacting with the Milky Way's hot gaseous halo for close to 1000~Myr, has a larger spatial extent than previously recognized, while also containing significant amounts of small-scale structure. After a brief consideration of the large-scale kinematics of the MS as traced by the recently-discovered extension of the MS, we explore the aging process of the MS gas through the operation of various hydrodynamic instabilities and interstellar turbulence. This in turn leads to consideration of processes whereby MS material survives as cool gas, and yet also evidently fails to form stars. Parallels between the MS and extragalactic tidal features are briefly discussed with an emphasis on steps toward establishing what the MS reveals about the critical role of local processes in determining the evolution of these kinds of systems.