The Geometry and Dynamical Role of Stellar Wind Bubbles in Photoionised HII Regions

TL;DR

This study uses 3D radiative magnetohydrodynamic simulations to explore how stellar winds influence the structure and dynamics of HII regions, finding winds have a minor role compared to photoionisation but create complex, chaotic bubble geometries.

Contribution

It provides the first detailed 3D simulations of wind bubbles in turbulent molecular clouds, highlighting their chaotic shapes and limited impact relative to radiation feedback.

Findings

Winds contribute about 10% of radial momentum compared to photoionisation.

Wind bubbles are highly aspherical and chaotic with chimneys and plumes.

Radiation pressure is negligible in the studied systems.

Abstract

Winds from young massive stars contribute a large amount of energy to their host molecular clouds. This has consequences for the dynamics and observable structure of star-forming clouds. In this paper, we present radiative magnetohydrodynamic simulations of turbulent molecular clouds that form individual stars of 30, 60 and 120 solar masses emitting winds and ultraviolet radiation following realistic stellar evolution tracks. We find that winds contribute to the total radial momentum carried by the expanding nebula around the star at 10 % of the level of photoionisation feedback, and have only a small effect on the radial expansion of the nebula. Radiation pressure is largely negligible in the systems studied here. The 3D geometry and evolution of wind bubbles is highly aspherical and chaotic, characterised by fast-moving "chimneys" and thermally-driven "plumes". These plumes can sometimes become disconnected from the stellar source due to dense gas flows in the cloud. Our results compare favourably with the findings of relevant simulations, analytic models and observations in the literature while demonstrating the need for full 3D simulations including stellar winds. However, more targeted simulations are needed to better understand results from observational studies.