# Quenching of supermassive black hole growth around the apparent maximum mass

## TL;DR

This study investigates the relationship between supermassive black hole mass and radio-loudness in quasars, suggesting that growth quenching occurs around a maximum mass of approximately 10^{10} solar masses, linked to accretion flow transitions.

## Contribution

It provides observational evidence connecting black hole mass thresholds with increased radio-loudness, supporting theories of growth quenching via accretion flow changes.

## Key findings

- Radio-loud quasar fraction increases above 10^{9.5} solar masses.
- Higher fraction of low Eddington ratio RL quasars above the mass threshold.
- Supports scenario of growth suppression near maximum SMBH mass.

## Abstract

Recent quasar surveys have revealed that supermassive black holes (SMBHs) rarely exceed a mass of $M_{\rm BH} \sim {\rm a~few}\times10^{10}~M_{\odot}$ during the entire cosmic history. It has been argued that quenching of the BH growth is caused by a transition of a nuclear accretion disk into an advection dominated accretion flow, with which strong outflows and/or jets are likely to be associated. We investigate a relation between the maximum mass of SMBHs and the radio-loudness of quasars with a well-defined sample of $\sim 10^5$ quasars at a redshift range of $0<z<2$, obtained from the Sloan Digital Sky Surveys DR7 catalog. We find that the number fraction of the radio-loud (RL) quasars increases above a threshold of $M_{\rm BH} \simeq 10^{9.5}~M_{\odot}$, independent of their redshifts. Moreover, the number fraction of RL quasars with lower Eddington ratios (out of the whole RL quasars), indicating lower accretion rates, increases above the critical BH mass. These observational trends can be natural consequences of the proposed scenario of suppressing BH growth around the apparent maximum mass of $\sim 10^{10}~M_{\odot}$. The ongoing VLA Sky Survey in radio will allow us to estimate of the exact number fraction of RL quasars more precisely, which gives further insights to understand quenching processes for BH growth.