Efficiently Cooled Stellar Wind Bubbles in Turbulent Clouds. II. Validation of Theory with Hydrodynamic Simulations

In a companion paper, we develop a theory for the evolution of stellar wind-driven bubbles in dense, turbulent clouds. This theory proposes that turbulent mixing at a fractal bubble/shell interface leads to highly efficient cooling, in which the vast majority of the input wind energy is radiated awa...

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Bibliographic Details
Published in:The Astrophysical journal 2021-06, Vol.914 (2), p.90
Main Authors: Lancaster, Lachlan, Ostriker, Eve C., Kim, Jeong-Gyu, Kim, Chang-Goo
Format: Article
Language:English
Subjects:
Astrophysics
Bubbles
Cloud formation
Clouds
Cooling
Eddy diffusion
Energy dissipation
Energy loss
Fractals
Molecular clouds
Momentum
Star & galaxy formation
Star clusters
Star formation
Stellar evolution
Stellar wind bubbles
Stellar winds
Turbulent diffusion
Turbulent mixing
Wind effects
Wind power
Young star clusters
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Summary:In a companion paper, we develop a theory for the evolution of stellar wind-driven bubbles in dense, turbulent clouds. This theory proposes that turbulent mixing at a fractal bubble/shell interface leads to highly efficient cooling, in which the vast majority of the input wind energy is radiated away. This energy loss renders the majority of the bubble evolution momentum driven rather than energy driven, with expansion velocities and pressures orders of magnitude lower than in the classical Weaver et al. solution. In this paper, we validate our theory with three-dimensional, hydrodynamic simulations. We show that extreme cooling is not only possible, but is generic to star formation in turbulent clouds over more than three orders of magnitude in density. We quantify the few free parameters in our theory, and show that the momentum exceeds the wind input rate by only a factor . We verify that the bubble/cloud interface is a fractal with dimension . The measured turbulent amplitude ( ) in the hot gas near the interface is shown to be consistent with theoretical requirements for turbulent diffusion to efficiently mix and radiate away most of the wind energy. The fraction of energy remaining after cooling is only , decreasing with time, explaining observations that indicate low hot-gas content and weak dynamical effects of stellar winds.
ISSN:0004-637X
1538-4357
DOI:10.3847/1538-4357/abf8ac