Reconstruction of Cosmic Black Hole Growth and Mass Distribution from Quasar Luminosity Functions at $z>4$: Implications for Faint and Low-mass Populations in JWST

Understand

The evolution of the quasar luminosity function (QLF) is fundamental to understanding the cosmic evolution of black holes (BHs) through their accretion phases.

• In the era of the James Webb Space Telescope (JWST), Euclid, and Nancy Grace Roman Space Telescope, their unprecedented detection sensitivity and wide survey area can unveil the low-luminosity quasar and low-mass BH population, and provide new insights into quasar host galaxies.
• We present a theoretical model describing BH growth from initial seeding at $z>20$ to $z\sim 4$,incorporating the duration of accretion episodes, the distribution of Eddington ratios, and the mass dependency of BH accretion rates.
• By constraining the model parameters with the observed QLFs at $4\leq z\leq6$ across a wide UV luminosity range ($-29<M_{\rm 1450}<-24$), we find that the high-redshift BH population grows rapidly at $z\gtrsim6$, and decelerates the pace in subsequent epochs.