The major mechanism to drive turbulence in star-forming galaxies

TL;DR

This study uses integral field spectroscopy to analyze the drivers of turbulence in star-forming galaxies, finding that both gravitational instability and stellar feedback contribute significantly, with feedback alone being insufficient.

Contribution

It provides observational evidence that turbulence in high-redshift, high-SFR galaxies results from combined effects of gravitational transport and stellar feedback, challenging models that consider feedback alone.

Findings

Both transport and feedback are needed to explain turbulence.

Stellar feedback alone under-predicts observed velocity dispersions.

Gravitational instability significantly contributes to turbulence.

Abstract

Two competing models, gravitational instability-driven transport and stellar feedback, have been proposed to interpret the high velocity dispersions observed in high-redshift galaxies. We study the major mechanisms to drive the turbulence in star-forming galaxies using a sample of galaxies from the xCOLD GASS survey, selected based on their star-formation rate (SFR) and gas fraction to be in the regime that can best distinguish between the proposed models. We perform Wide Field Spectrograph (WiFeS) integral field spectroscopic (IFS) observations to measure the intrinsic gas velocity dispersions, circular velocities and orbital periods in these galaxies. Comparing the relation between the SFR, velocity dispersion, and gas fraction with predictions of these two theoretical models, we find that our results are most consistent with a model that includes both transport and feedback as drivers of turbulence in the interstellar medium. By contrast, a model where stellar feedback alone drives turbulence under-predicts the observed velocity dispersion in our galaxies, and does not reproduce the observed trend with gas fraction. These observations therefore support the idea that gravitational instability makes a substantial contribution to turbulence in high redshift and high SFR galaxies.