Large-scale Turbulent Driving Regulates Star Formation in High-redshift Gas-rich Galaxies

Abstract : The question of what regulates star formation is a long standing issue. To investigate this issue, we run simulations of a kiloparsec cube section of a galaxy with three kinds of stellar feedback: the formation of HII regions, the explosion of supernovae, and the UV heating. We show that stellar feedback is sufficient to reduce the averaged star formation rate (SFR) to the level of the Schmidt- Kennicutt law in Milky-Way like galaxies but not in high-redshift gas rich galaxies suggesting that another type of support should be added. We investigate whether an external driving of the turbulence such as the one created by the large galactic scales could diminish the SFR at the observed level. Assuming that the Toomre parameter is close to 1 as suggested by the observations, we infer a typical turbulent forcing that we argue should be applied parallel to the plane of the galactic disc. When this forcing is applied in our simulations, the SFR within our simulations closely follows the Schmidt- Kennicutt relation. We found that the velocity dispersion is strongly anisotropic with the velocity dispersion alongside the galactic plane being up to 10 times larger than the perpendicular velocity.