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ABSTRACT In large-scale hydrodynamical cosmological simulations, the fate of massive galaxies is mainly dictated by the modelling of feedback from active galactic nuclei (AGNs). The amount of energy released by AGN feedback is proportional to the mass that has been accreted on to the black holes (BHs), but the exact subgrid modelling of AGN feedback differs in all simulations. While modern simulations reliably produce populations of quiescent massive galaxies at z ≤ 2, it is also crucial to assess the similarities and differences of the responsible AGN populations. Here, we compare the AGN populations of the Illustris, TNG100, TNG300, Horizon-AGN, EAGLE, and SIMBA simulations. The AGN luminosity function (LF) varies significantly between simulations. Although in agreement with current observational constraints at z = 0, at higher redshift the agreement of the LFs deteriorates with most simulations producing too many AGNs of $$L_{\rm x, 2\!-\!10 \, keV}\sim 10^{43\!-\!44}\, \rm erg\, s^{-1}$$. AGN feedback in some simulations prevents the existence of any bright AGN with $$L_{\rm x, 2\!-\!10 \, keV}\geqslant 10^{45}\rm \,erg\, s^{-1}$$ (although this is sensitive to AGN variability), and leads to smaller fractions of AGN in massive galaxies than in the observations at z ≤ 2. We find that all the simulations fail at producing a number density of AGN in good agreement with observational constraints for both luminous ($$L_{\rm x, 2\!-\!10 \, keV}\sim 10^\text{43-45}\, \rm erg\, s^{-1}$$) and fainter ($$L_{\rm x, 2\!-\!10 \, keV}\sim 10^\text{42-43}\, \rm erg\, s^{-1}$$) AGNs and at both low and high redshifts. These differences can aid us in improving future BH and galaxy subgrid modelling in simulations. Upcoming X-ray missions (e.g. Athena, AXIS, and LynX) will bring faint AGNs to light and new powerful constraints. After accounting for AGN obscuration, we find that the predicted number density of detectable AGNs in future surveys spans at least one order of magnitude across the simulations, at any redshift. 

ABSTRACT We perform a consistent comparison of the mass and mass profiles of massive (M⋆ > 1011.4 M⊙) central galaxies at z ∼ 0.4 from deep Hyper Suprime-Cam (HSC) observations and from the Illustris, TNG100, and Ponos simulations. Weak lensing measurements from HSC enable measurements at fixed halo mass and provide constraints on the strength and impact of feedback at different halo mass scales. We compare the stellar mass function (SMF) and the Stellar-to-Halo Mass Relation (SHMR) at various radii and show that the radius at which the comparison is performed is important. In general, Illustris and TNG100 display steeper values of α where $$M_{\star } \propto M_{\rm vir}^{\alpha }$$. These differences are more pronounced for Illustris than for TNG100 and in the inner rather than outer regions of galaxies. Differences in the inner regions may suggest that TNG100 is too efficient at quenching in situ star formation at Mvir ≃ 1013 M⊙ but not efficient enough at Mvir ≃ 1014 M⊙. The outer stellar masses are in excellent agreement with our observations at Mvir ≃ 1013 M⊙, but both Illustris and TNG100 display excess outer mass as Mvir ≃ 1014 M⊙ (by ∼0.25 and ∼0.12 dex, respectively). We argue that reducing stellar growth at early times in $$M_\star \sim 10^{9-10} \, \mathrm{M}_{\odot }$$ galaxies would help to prevent excess ex-situ growth at this mass scale. The Ponos simulations do not implement AGN feedback and display an excess mass of ∼0.5 dex at r < 30 kpc compared to HSC which is indicative of overcooling and excess star formation in the central regions. The comparison of the inner profiles of Ponos and HSC suggests that the physical scale over which the central AGN limits star formation is r ≲ 20 kpc. Joint comparisons between weak lensing and galaxy stellar profiles are a direct test of whether simulations build and deposit galaxy mass in the correct dark matter haloes and thereby provide powerful constraints on the physics of feedback and galaxy growth. Our galaxy and weak lensing profiles are publicly available to facilitate comparisons with other simulations. 

ABSTRACT The past decade has seen significant progress in understanding galaxy formation and evolution using large-scale cosmological simulations. While these simulations produce galaxies in overall good agreement with observations, they employ different sub-grid models for galaxies and supermassive black holes (BHs). We investigate the impact of the sub-grid models on the BH mass properties of the Illustris, TNG100, TNG300, Horizon-AGN, EAGLE, and SIMBA simulations, focusing on the MBH − M⋆ relation and the BH mass function. All simulations predict tight MBH − M⋆ relations, and struggle to produce BHs of $$M_{\rm BH}\leqslant 10^{7.5}\, \rm M_{\odot }$$ in galaxies of $$M_{\star }\sim 10^{10.5}\!-\!10^{11.5}\, \rm M_{\odot }$$. While the time evolution of the mean MBH − M⋆ relation is mild ($$\rm \Delta M_{\rm BH}\leqslant 1\, dex$$ for 0 $$\leqslant z \leqslant$$ 5) for all the simulations, its linearity (shape) and normalization varies from simulation to simulation. The strength of SN feedback has a large impact on the linearity and time evolution for $$M_{\star }\leqslant 10^{10.5}\, \rm M_{\odot }$$. We find that the low-mass end is a good discriminant of the simulation models, and highlights the need for new observational constraints. At the high-mass end, strong AGN feedback can suppress the time evolution of the relation normalization. Compared with observations of the local Universe, we find an excess of BHs with $$M_{\rm BH}\geqslant 10^{9}\, \rm M_{\odot }$$ in most of the simulations. The BH mass function is dominated by efficiently accreting BHs ($$\log _{10}\, f_{\rm Edd}\geqslant -2$$) at high redshifts, and transitions progressively from the high-mass to the low-mass end to be governed by inactive BHs. The transition time and the contribution of active BHs are different among the simulations, and can be used to evaluate models against observations.