# The SAMI Galaxy Survey: energy sources of the turbulent velocity dispersion in spatially-resolved local star-forming galaxies

## TL;DR

This study examines the energy sources behind turbulent motions in ionised gas within local star-forming galaxies, revealing that factors beyond star formation feedback, such as gravity and galactic shear, likely drive turbulence.

## Contribution

It provides observational evidence that additional mechanisms besides feedback influence turbulence in star-forming galaxies, challenging existing models.

## Key findings

- Velocity dispersion is flat across SFR surface densities.
- Many galaxies show higher dispersion than feedback models predict.
- Gravity and galactic shear may contribute to turbulence.

## Abstract

We investigate the energy sources of random turbulent motions of ionised gas from H$\alpha$ emission in eight local star-forming galaxies from the Sydney-AAO Multi-object Integral field spectrograph (SAMI) Galaxy Survey. These galaxies satisfy strict pure star-forming selection criteria to avoid contamination from active galactic nuclei (AGN) or strong shocks/outflows. Using the relatively high spatial and spectral resolution of SAMI, we find that -- on sub-kpc scales our galaxies display a flat distribution of ionised gas velocity dispersion as a function of star formation rate (SFR) surface density. A major fraction of our SAMI galaxies shows higher velocity dispersion than predictions by feedback-driven models, especially at the low SFR surface density end. Our results suggest that additional sources beyond star formation feedback contribute to driving random motions of the interstellar medium (ISM) in star-forming galaxies. We speculate that gravity, galactic shear, and/or magnetorotational instability (MRI) may be additional driving sources of turbulence in these galaxies.