Role of Cosmic Ray Streaming and Turbulent Damping in Driving Galactic Winds

TL;DR

This study investigates how cosmic ray streaming and turbulence-driven damping influence galactic winds, revealing that turbulence suppresses cosmic ray streaming, leading to more extended gas distributions and affecting star formation and wind mass loading.

Contribution

It introduces a realistic model of cosmic ray streaming suppression due to turbulence, improving understanding of galactic wind dynamics in magnetized interstellar media.

Findings

Turbulent damping causes more extended gas and cosmic ray distributions.

Star formation rate increases with turbulence level.

Wind mass loading decreases as turbulence strength increases.

Abstract

Large-scale galactic winds driven by stellar feedback are one phenomenon that influences the dynamical and chemical evolution of a galaxy, redistributing material throughout the circumgalatic medium. Non-thermal feedback from galactic cosmic rays (CRs) -high-energy charged particles accelerated in supernovae and young stars - can impact the efficiency of wind driving. The streaming instability limits the speed at which they can escape. However, in the presence of turbulence, the streaming instability is subject to suppression that depends on the magnetization of turbulence given by its Alfv\'en Mach number. While previous simulations that relied on a simplified model of CR transport have shown that super-Alfv\'enic streaming of CRs enhances galactic winds, in the present paper we take into account a realistic model of streaming suppression. We perform three-dimensional magnetohydrodynamic simulations of a section of a galactic disk and find that turbulent damping dependent on local magnetization of turbulent interstellar medium (ISM) leads to more spatially extended gas and CR distributions compared to the earlier streaming calculations, and that scale-heights of these distributions increase for stronger turbulence. Our results indicate that the star formation rate increases with the level of turbulence in the ISM. We also find that the instantaneous wind mass loading is sensitive to local streaming physics with the mass loading dropping significantly as the strength of turbulence increases.