Pumping Iron: How Turbulent Metal Diffusion Impacts Multiphase Galactic Outflows

Most numerical simulations of galaxy formation and evolution are unable to properly resolve the turbulent cascade at or below the resolution scale and turbulence models are required to capture the motion of eddies on those unresolved scales. We investigate the impact of turbulent metal diffusion on multiphase outflows originating from dwarf galaxies (M_halo ∼ 10¹⁰−10¹¹ M_⊙). We use our state-of-the-art numerical model for the formation of single stars and nonequilibrium cooling and chemistry. We run the simulations at a resolution of ∼4 M_⊙, and resolve individual supernova explosions in terms of hot phase and momentum input. We find that the mass, energy, and metal loading factors are only weakly affected by the inclusion of a metal diffusion model. The metal enrichment factor at low altitudes above the galactic disk is higher by around 20% when the metal diffusion model is included. Specifically, we find more efficient cooling in the cold interstellar medium, due to more efficient metal mixing that leads to shorter cooling times of the warm gas, which becomes available more quickly for star formation. The most striking effect of the metal diffusion model is that, without metal diffusion, there is more rapid cooling in the hot phase and a reduced sound speed by a factor of 2. Specifically, we find that the hot phase is more metal enriched in the case without metal diffusion leading to more rapid overcooling of that phase, which is consistent with the higher sound speed we find in the runs with metal diffusion.