Evidence for supernova feedback sustaining gas turbulence in nearby star-forming galaxies

TL;DR

This study demonstrates that supernova feedback, with a coupling efficiency of about 1%, can sustain the observed turbulence in the cold gas of nearby star-forming galaxies by accounting for increased dissipation timescales due to gas disc flaring.

Contribution

It introduces the idea that disc thickness and flaring extend turbulence dissipation timescales, reducing the energy needed from supernovae to sustain turbulence.

Findings

SN feedback with ~1% energy coupling sustains turbulence.

Gas disc flaring increases turbulence dissipation timescale.

Theoretical predictions align with observational data.

Abstract

HI and CO observations indicate that the cold gas in galaxies is very turbulent. However, the turbulent energy is expected to be quickly dissipated, implying that some energy source is needed to explain the observations. The nature of such turbulence was long unclear, as even the main candidate, supernova (SN) feedback, seemed insufficient. Other mechanisms have been proposed, but without reaching a general consensus. The key novelty of our work is considering that the gas disc thickness and flaring increase the dissipation timescale of turbulence, thus reducing the energy injection rate required to sustain it. In excellent agreement with the theoretical expectations, we found that the fraction of the SN energy (a.k.a. SN coupling efficiency) needed to maintain the cold gas turbulence is $\sim 1$%, solving a long-standing conundrum.