What controls the ionized gas turbulent motions in dwarf galaxies?

Using three-dimensional (3D) spectroscopy with a scanning Fabry-Perot interferometer, we study the kinematics of ionized gas in 59 nearby dwarf galaxies. Combining our results with data from the literature, we provide a global relation between the gas velocity dispersion σ and the star formation rate (SFR) and Hα luminosity for galaxies with a very broad range of star formation rates: SFR = 0.001-300 M_⊙ yr^-1. We find that the SFR-σ relation for the combined sample of dwarf galaxies, star-forming, local luminous and ultraluminous infrared galaxies can be fitted in the form σ ∝ SFR^{5.3 ± 0.2}. This implies that the slope of the L-σ relation inferred from a sample of rotation-supported disc galaxies (including mergers) is similar to the L-σ relation of individual giant H II regions. We present arguments that the velocity dispersion of the ionized gas does not reflect virial motions in the gravitational potential of dwarf galaxies and instead is determined mainly by the energy injected into the interstellar medium by ongoing star formation.