Regulation of star formation by large-scale gravitoturbulence

A simple model for star formation based on supernova (SN) feedback and gravitational heating via the collapse of perturbations in gravitationally unstable discs reproduces the Schmidt-Kennicutt relation between the star formation rate (SFR) per unit area, ςSFR, and the gas surface density, ςg, remarkably well. The gas velocity dispersion, σg, is derived self-consistently in conjunction with ςSFR and is found to match the observations. Gravitational instability triggers 'gravitoturbulence' at the scale of the least stable perturbation mode, boosting σg at Σg ≥ Σgthr=50 M\odot, pc-2, and contributing to the pressure needed to carry the disc weight vertically. ςSFR is reduced to the observed level at Σg ≥ Σgthr, whereas at lower surface densities, SN feedback is the prevailing energy source. Our proposed star formation recipes require efficiencies of the order of 1 per cent, and the Toomre parameter, Q, for the joint gaseous and stellar disc is predicted to be close to the critical value for marginal stability for Σg ≥ Σgthr, spreading to lower values and larger gas velocity dispersion at higher ςg.