Supermassive black holes in cosmological simulations I: MBH − M⋆ relation and black hole mass function

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 ≤ z ≤ 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 (log10 fEdd ≥ −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.

Subaru High-z Exploration of Low-luminosity Quasars (SHELLQs). XIII. Large-scale Feedback and Star Formation in a Low-luminosity Quasar at z = 7.07 on the Local Black Hole to Host Mass Relation

“…Further observations of galaxies hosting less massive SMBHs are necessary to confirm this picture statistically. As the coevolution relation is the end product of the complex growth of galaxies and SMBHs, a statistical measurement of this relation at the early universe (see also, e.g., Suh et al 2020;Setoguchi et al 2021) would help constrain the relative cosmological importance of various feeding and feedback processes (Habouzit et al 2021). We also need high-resolution observations sensitive to detailed dynamics, as well as wide-area deep observations sensitive to the surrounding environments, to reveal the driving mechanism of the rapid growth of galaxies and SMBHs in the early universe.…”

Quasar clustering at redshift 6

“…In order to better probe the exact epoch and search volume of our observational QSO sample, we carried out a census of bright AGN pairs at z = 6 in the Illustris-TNG300 (hereafter TNG300) and L-Galaxies 2020 galaxy evolution models. TNG300 (Pillepich et al 2018;Springel et al 2018;Naiman et al 2018;Marinacci et al 2018;Nelson et al 2018) is a magneto-hydrodynamical simulation run in a (205 h −1 Mpc) 3 box, using a Bondi-Hoyle-Lyttleton BH accretion model with no boost factor but an assumed BH seed mass of 8 × 10 5 M (see Habouzit et al 2021). L-Galaxies 2020 (Henriques et al 2020) is a semi-analytic model run on the larger (480 h −1 Mpc) 3 Millennium-I box (Springel et al 2005), but with a more simplified phenomenological model of quasar-and radio-mode BH accretion and no BH seed mass (see Croton et al 2006).…”

“…Currently, cosmologicalscale simulations typically either focus on quasar properties below z ∼ 5 due to improved statistics (e.g., DeGraf & Sijacki 2017;Bhowmick et al 2019;Habouzit et al 2021) or above z ∼ 7 due to reduced computational limitations (e.g., DiMatteo et al 2017;Tenneti et al 2019;Marshall et al 2020). Zoom-in simulations of halos containing QSOs at z ∼ 6−7 have been performed (e.g.,Costa et al 2014;Lupi et al 2019); however, they do not readily provide statistics on large scales.…”

The black hole population in low-mass galaxies in large-scale cosmological simulations

“…Such simulations have been successful at producing galaxies in good agreement with the properties of observed galaxies. Nevertheless, discrepancies among the simulations exist and arise from the use of different galaxy and BH subgrid physics (Habouzit et al 2021). The formation of BHs in these simulations does not follow the theoretical prescriptions of BH formation mechanisms.…”