A Bayesian approach to the halo galaxy – supermassive black hole connection through cosmic time

Aims. The evolution of dark matter halos, galaxies, and supermassive black holes are deeply interdependent. We study whether this co-evolution can be qualitatively understood by connecting the evolution of a dark matter structure with simple empirical prescriptions for baryonic processes. Methods. We established expressions for the (star-forming) galaxy stellar mass function, galaxy UV luminosity function, active black hole mass function, and quasar bolometric luminosity function by assuming a direct and physically motivated relationship between the properties of galaxies and supermassive black holes, and the mass of their host halo. We calibrated the baryonic prescriptions using a fully Bayesian approach to reproduce observed population statistics. The derived parameterisations were then utilised to investigate the connection between galaxy and black hole characteristics and how these characteristics change with redshift. Results. The galaxy stellar mass – UV luminosity relation, black hole mass – stellar mass relation, black hole mass – AGN luminosity relation, and redshift evolution of these quantities obtained from the model are qualitatively consistent with observations. Based on these results, we present upper limits on the expected number of sources for z = 5 up to z = 15 for scheduled JWST and Euclid surveys, thus showcasing that empirical models can offer qualitative predictions at a high redshift in a fast, easy, and flexible manner that complements more computationally expensive approaches.