# On the formation of the first quasars

## TL;DR

This paper reviews theoretical models explaining how the first supermassive black holes and their host galaxies rapidly formed and evolved by redshift z>6, addressing their growth and chemical maturity.

## Contribution

It provides a comprehensive overview of current models on the formation and evolution of early quasars and their host galaxies at high redshift.

## Key findings

- Supermassive black holes (>10^9 Msun) existed at z>6.
- Host galaxies had metallicities and dust similar to local galaxies.
- Models highlight conditions for seed black hole formation and growth.

## Abstract

Observations of the most luminous quasars at redshift z>6 reveal the existence of numerous supermasssive black holes (>10^9 Msun) already in place about twelve billion years ago. In addition, the interstellar medium of the galaxies hosting these black holes are observed to be chemically mature systems, with metallicities (Z>Zsun) and dust masses (>10^8 Msun) similar to that of more evolved, local galaxies. The connection between the rapid growth of the first supermassive black holes and the fast chemical evolution of the host galaxy is one of the most puzzling issues for theoretical models. Here we review state-of-the-art theoretical models that focus on this problem with particular emphasis on the conditions that lead to the formation of quasar seeds and their subsequent evolution at z>6.