Towards simulating star formation in turbulent high-z galaxies with mechanical supernova feedback

To better understand the impact of supernova (SN) explosions on the evolution of galaxies, we perform a suite of high-resolution (12 pc), zoom-in cosmological simulations of a Milky Way-like galaxy at z = 3 with adaptive mesh refinement. We find that SN explosions can efficiently regulate star formation, leading to the stellar mass and metallicity consistent with the observed mass-metallicity relation and stellar mass-halo mass relation at z ∼ 3. This is achieved by making three important changes to the classical feedback scheme: (i) the different phases of SN blast waves are modelled directly by injecting radial momentum expected at each stage, (ii) the realistic time delay of SNe is required to disperse very dense gas before a runaway collapse sets in, and (iii) a non-uniform density distribution of the interstellar medium (ISM) is taken into account below the computational grid scale for the cell in which an SN explodes. The simulated galaxy with the SN feedback model shows strong outflows, which carry approximately 10 times larger mass than star formation rate, as well as smoothly rising circular velocity. Although the metallicity of the outflow depends sensitively on the feedback model used, we find that the accretion rate and metallicity of the cold flow around the virial radius is impervious to SN feedback. Our results suggest that understanding the structure of the turbulent ISM may be crucial to assess the role of SN and other feedback processes in galaxy formation theory.