SIMBA: Cosmological simulations with black hole growth and feedback

We introduce the SIMBA simulations, the next generation of the MUFASA cosmological galaxy formation simulations run with GIZMO's meshless finite mass hydrodynamics. SIMBA includes updates to MUFASA's sub-resolution star formation and feedback prescriptions, and introduces black hole growth via the torque-limited accretion model of Anglés-Alcázar et al. from cold gas and Bondi accretion from hot gas, along with black hole feedback via kinetic bipolar outflows and X-ray energy. Ejection velocities are taken to be ∼103 km s-1 at high Eddington ratios, increasing to ∼8000 km s-1 at Eddington ratios below 2 per cent, with a constant momentum input of 20L/c. SIMBA further includes an on-the-fly dust production, growth, and destruction model. Our SIMBA run with (100h -1 Mpc)3 and 10243 gas elements reproduces numerous observables, including galaxy stellar mass functions at z = 0-6, the stellar mass- star formation rate main sequence, HI and H2 fractions, the mass-metallicity relation at z ∼ 0, 2, star-forming galaxy sizes, hot gas fractions in massive haloes, and z = 0 galaxy dust properties. However, SIMBA also yields an insufficiently sharp truncation of the z = 0 mass function, and too-large sizes for low-mass quenched galaxies. We show that SIMBA's jet feedback is primarily responsible for quenching massive galaxies.