We investigate the scaling relation between black hole (BH) and stellar mass (M• − M*), diagnosing the residual Δlog(M•/M⊙) (Δ) in this relation to understand the coevolution of galaxies and BHs in the cosmological hydrodynamic simulation SIMBA. We show that SIMBA reproduces the observed M• − M* relation well, with little difference between central and satellite galaxies. By using the median value to determine the residuals, we find that the residual correlates with galaxy cold gas content, star formation rate, colour, and BH accretion properties. Both torque and Bondi models implemented in SIMBA contribute to this residual, with torque accretion playing a major role in high-redshift and low-mass galaxies, while Bondi (including BH mergers) dominates at low redshift and massive galaxies. By dividing the sample into two populations (Δ > 0 and Δ IMBA.
Ma et al. (Fri,) studied this question.