Population synthesis of active galactic nuclei based on the radiation-regulated unification model

Vollständiger Abstract

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X-ray surveys of active galactic nuclei (AGNs) provide direct constraints on the properties of individual AGNs, such as their emission, obscuration, and accretion rate. Previous AGN population synthesis models have not addressed such properties self-consistently. For this study, we used a simulation-based inference (SBI) approach to constrain the geometrical and physical properties of the AGN population. We performed numerical simulations with our ray-tracing code, , which allows the self-consistent modelling of the X-ray emission of AGNs with flexible circumnuclear and source geometries. We created our synthetic population by sampling the intrinsic active black hole mass function (BHMF) and Eddington ratio distribution function (ERDF) of local AGNs, and we constructed a geometry based on the radiation-regulated model, along with Eddington-ratio-dependent emission spectra. Using the -simulated emission of the AGN population, we aimed to simultaneously reproduce the cosmic X-ray background (CXB), differential AGN number counts, and several observed absorption properties of local AGNs, such as the fraction of in bins of log( ), the Compton-thick fraction as a function of the limiting flux, and the number of obscured and unobscured AGNs as a function of the Eddington ratio. With this approach, we tested the consistency of the radiation-regulated model with a very comprehensive set of X-ray observables, while constraining the size and density of the dusty torus and the evolution of the local AGN population. We derive an intrinsic Compton-thick fraction of 40 RefleX RefleX and find that a simple evolutionary prescription controlling the active fraction of supermassive black holes is sufficient for our synthetic population to reproduce the CXB. Finally, we compare the inferred dusty torus structure to observations and examine the dependence of the covering factor on Eddington ratio, the observed correlation between reflection and obscuration, and the BHMFs and ERDFs of obscured and unobscured AGNs.