The geometry and dynamical role of stellar wind bubbles in photoionized H ii regions

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.

PHANGS–ALMA: Arcsecond CO(2–1) Imaging of Nearby Star-forming Galaxies

“…The density, turbulence, and self-gravity may also determine how the new-born stars cluster (e.g., Kruijssen 2012;Hopkins 2013;Krumholz & McKee 2020;Grudić et al 2021). The local gas (column) density distribution may also interact with sources of stellar feedback to determine whether a cloud is disrupted or not and how much gas and radiation leaves the system (e.g., Thompson et al 2005;Walch et al 2015;Geen et al 2016;Raskutti et al 2016Raskutti et al , 2017Thompson & Krumholz 2016;Kim et al 2018Kim et al , 2019Reissl et al 2018;Geen et al 2021). Because the timescale, efficiency, and spatial clustering of star formation and feedback have a qualitative impact on the GMC-scale gas properties (e.g., Hopkins et al 2013;Gentry et al 2017;, star formation, stellar feedback, and GMC properties form a complex, multiscale system with many types of physics at play.…”

Stellar winds and photoionization in a spiral arm

“…With efficient cooling, the expansion of the bubble is driven by the ram pressure of the free-streaming wind colliding with the mixed shell. This has been found to occur in simulations of turbulent clouds by Geen et al (2021) and Lancaster et al (2021a). This extreme case permits simpler implementations of feedback in the form of momentum-conserving winds (Dale & Bonnell 2008).…”

“…Dale et al 2005;Mellema et al 2006;Peters et al 2010;Arthur et al 2011;Walch et al 2012;Colín et al 2013;Geen et al 2015;Howard et al 2016;Gavagnin et al 2017;Ali et al 2018;Kim et al 2018;Zamora-Avilés et al 2019;Vandenbroucke & Wood 2019;Bending et al 2020;Fukushima et al 2020;Sartorio et al 2021). However, fewer studies have focused on stellar winds (Dale & Bonnell 2008;Rogers & Pittard 2013;Rey-Raposo et al 2017;Offner & Liu 2018;Wareing et al 2018), particularly in combination with radiation (Dale et al 2014;Ngoumou et al 2015;Haid et al 2018;Geen et al 2021). Winds are a difficult problem to solve computationally due to the extreme temperatures (10 7 K) and velocities (10 3 km s −1 ) involved, as well the radiative processes required to model the cooling of hot, shocked gas (and the spatial resolution needed to resolve this).…”

How to inflate a wind-blown bubble

“…Another possibility is to inject mass, momentum and energy evenly into all cells (Geen et al 2021). The procedure is:…”

“…(iv) Although not explicitly stated by Geen et al (2021), in order to conserve energy the internal energy density of the cell must become e int,new = e tot,new − 0.5ρ new v 2 new . In this scenario, the stationary flow develops so that the density and pressure within the injection region increase with radius (in contrast to method ei where these quantities decline), and the velocity of gas within the injection region is everywhere equal to the wind speed (like the fixed speed overwrite procedure in Sec.…”