The origin of the JWST supermassive black holes

We present a new semi-analytical model for the evolution of galaxies and supermassive black holes (SMBHs) that is based on the extended Press-Schechter formalism and phenomenological modelling of star formation. The model yields black-hole-mass – stellar mass relations that reproduce both the JWST and pre-JWST observations. If the efficiency for BH mergers is high, the JWST data prefer light seeds, while the pre-JWST data prefer heavy seeds. The fit improves for a smaller merger efficiency, 𝒪(0.1), for which both data prefer heavy seeds, while also accommodating the pulsar-timing-array gravitational-wave background data.