AGN radiative feedback in the early growth of massive black holes

TL;DR

This paper investigates how radiation pressure on dust from active galactic nuclei influences the early growth of massive black holes, showing that such feedback can drive outflows consistent with high-redshift quasar observations.

Contribution

It introduces a model of AGN radiative dusty feedback affecting early black hole growth, highlighting its role in galactic outflows at high redshifts.

Findings

Outflow energetics are modest, with momentum flux $ ot p \\lesssim L/c$ and kinetic power $ ot E_k \\lesssim 10^{-3} L$.

Radiation pressure-driven outflows follow exponential trends during black hole growth.

Feedback effects are significant in powering early galactic outflows, aligning with observations of high-redshift quasars.

Abstract

Growing observational evidence confirms the existence of massive black holes ($M_{BH} \sim 10^9 M_{\odot}$), accreting at rates close to the Eddington limit, at very high redshifts ($z \gtrsim 6-7$) in the early Universe. Recent observations indicate that the host galaxies of the first quasars are chemically evolved systems, containing unexpectedly large amounts of dust. Such a combination of high luminosities and large dust content should form favourable physical conditions for radiative dusty feedback. We explore the impact of the active galactic nucleus (AGN) feedback, driven by radiation pressure on dust, on the early growth of massive black holes. Assuming Eddington-limited exponential black hole growth, we find that the dynamics and energetics of the radiation pressure-driven outflows also follow exponential trends at late times. We obtain modest outflow energetics (with momentum flux $\dot{p} \lesssim L/c$ and kinetic power $\dot{E}_{k} \lesssim 10^{-3} L$), comparable with available observations of quasar-driven outflows at very high redshifts, but significantly lower than typically observed in local quasars and predicted by wind energy-driven models. AGN radiative dusty feedback may thus play an important role in powering galactic outflows in the first quasars in the early Universe.