  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.
