高红移黑洞和类星体光度函数的演化
The assembly of black hole mass and high-z quasar luminosity functions
The early evolution of the quasar luminosity function (QLF) and black hole mass function (BHMF) encodes key information on the physics determining the radiative and accretion processes of supermassive black holes (BHs) in high-z quasars. Multiple-band quasar surveys have constrained the QLF shape at high-z, yet it remains challenging to develop a theoretical model that explains its redshift evolution associated with BH growth self-consistently. Based on a semi-analytical model for the BH formation and growth, we model the evolution of QLF and BHMF where the early BH population experiences multiple accretion bursts, in each of which a constant Eddington ratio is assigned following a Schechter distribution function. Our best-fit model to reproduce the observed QLF and BHMF at z>6 suggests that several episodes of moderate super-Eddington accretion occur and each of them lasts for ~20-30 Myr. We find that the observed Eddington-ratio distribution function is skewed to a log-normal shape owing to detection limits of quasar surveys, which offers a benchmark for future observational tests. At lower redshifts z~5-4, the best-fit parameters indicate that the BH growth is stunted, especially in the high-mass end, which leads to a saturation of BHMF at M>10^10 Msun. These results will be unveiled by future deep and wide surveys with the James Webb Space Telescope, Nancy Roman Space Telescope, and Euclid.
