Concordance between observations and simulations in the evolution of the mass relation between supermassive black holes and their host galaxies

TL;DR

This study compares observed and simulated relations between supermassive black hole mass and host galaxy stellar mass across redshifts, finding good agreement in scatter and highlighting the importance of feedback models.

Contribution

It provides a comprehensive comparison of observations and multiple simulations, revealing the role of feedback mechanisms and the importance of observational sensitivity in studying black hole-galaxy relations.

Findings

Simulations predict scatter similar to observations across redshifts.

Horizon-AGN and TNG best match observed relations at different redshifts.

Feedback models influence the tightness of the black hole-galaxy mass relation.

Abstract

We carry out a comparative analysis of the relation between the mass of supermassive black holes (BHs) and the stellar mass of their host galaxies at $0.2<z<1.7$ using well-matched observations and multiple state-of-the-art simulations (e.g., Massive Black II, Horizon-AGN, Illustris, TNG and a semi-analytic model). The observed sample consists of 646 uniformly-selected SDSS quasars ($0.2 < z < 0.8$) and 32 broad-line active galactic nuclei (AGNs; $1.2<z<1.7$) with imaging from Hyper Suprime-Cam (HSC) for the former and Hubble Space Telescope (HST) for the latter. We first add realistic observational uncertainties to the simulation data and then construct a simulated sample in the same manner as the observations. Over the full redshift range, our analysis demonstrates that all simulations predict a level of intrinsic scatter of the scaling relations comparable to the observations which appear to agree with the dispersion of the local relation. Regarding the mean relation, Horizon-AGN and TNG are in closest agreement with the observations at low and high redshift ($z\sim$ 0.2 and 1.5, respectively) while the other simulations show subtle differences within the uncertainties. For insight into the physics involved, the scatter of the scaling relation, seen in the SAM, is reduced by a factor of two and closer to the observations after adopting a new feedback model that considers the geometry of the AGN outflow. The consistency in the dispersion with redshift in our analysis supports the importance of both quasar- and radio-mode feedback prescriptions in the simulations. Finally, we highlight the importance of increasing the sensitivity (e.g., using the James Webb Space Telescope), thereby pushing to lower masses and minimizing biases due to selection effects.