# Supermassive black holes at high redshifts

## TL;DR

A new MeV telescope survey will detect over 1000 blazars up to redshift 6, enabling insights into early supermassive black hole formation, jet emission regions, and accretion-spin interactions.

## Contribution

The paper proposes that a next-generation MeV telescope can significantly advance understanding of supermassive black holes and jet physics at high redshifts.

## Key findings

- Detection of >1000 MeV blazars up to z=6
- Probing black hole formation and growth mechanisms
- Locating emission regions in powerful blazars

## Abstract

MeV blazars are the most luminous persistent sources in the Universe and emit most of their energy in the MeV band. These objects display very large jet powers and accretion luminosities and are known to host black holes with a mass often exceeding $10^9 M_{\odot}$. An MeV survey, performed by a new generation MeV telescope which will bridge the entire energy and sensitivity gap between the current generation of hard X-ray and gamma-ray instruments, will detect $>$1000 MeV blazars up to a redshift of $z=5-6$. Here we show that this would allow us: 1) to probe the formation and growth mechanisms of supermassive black holes at high redshifts, 2) to pinpoint the location of the emission region in powerful blazars, 3) to determine how accretion and black hole spin interplay to power the jet.