Abstract

Active galactic nuclei (AGN) in the early Universe are thought to be prominent sources of energy and ionizing photons that affected the growth of their host galaxy and environment. However, how the supermassive black holes (SMBHs) that fuel these AGN grew to the observed high masses already at high redshifts and the overall effects of their feedback are still unclear. Observations of high-redshift SMBH progenitors or lower-mass AGN will thus help characterize the evolution of SMBHs and their impact on the surroundings. With the launch of the JWST, fainter objects at high redshifts can now be detected, including lower-mass AGN. To assess AGN effects, we start with an analytical model of SMBHs to study the maximal and most optimistic global AGN feedback. The model does not overproduce the known observations and provides an upper limit to AGN radiation. We then assess the observability of low luminosity AGN using a cosmological simulation to provide a realistic environment for black hole growth in the early Universe. The SMBH seeds placed in the cosmological environment do not significantly accrete and grow to reach masses that can be observed with the JWST under conditions of standard Bondi-Hoyle accretion, as energy input from stellar feedback prevents efficient gas accretion onto the black holes. To be observed with the JWST, rarer but still physically feasible growth regimes, involving Eddington or super-Eddington accretion, would be required. Alternatively, AGN observability may be boosted under even rarer conditions of extreme gravitational lensing.