The odd couple: quasars and black holes

TL;DR

This paper discusses quasars powered by supermassive black holes, their prevalence in galaxies, and explores the relationship between black hole mass and galaxy properties, highlighting unresolved questions about their formation and influence.

Contribution

It reviews the current understanding of quasar energy sources, black hole presence in galaxies, and the correlation between black hole and galaxy properties, emphasizing open research questions.

Findings

Quasars are powered by supermassive black holes.

Most galaxies host central black holes of varying masses.

Black hole mass correlates with galaxy properties.

Abstract

Quasars emit more energy than any other objects in the universe, yet are not much bigger than the solar system. We are almost certain that quasars are powered by giant black holes of up to $10^{10}$ times the mass of the Sun, and that black holes of between $10^6$ and $10^{10}$ solar masses---dead quasars---are present at the centers of most galaxies. Our own galaxy contains a black hole of $4.3\times10^6$ solar masses. The mass of the central black hole appears to be closely related to other properties of its host galaxy, such as the total mass in stars, but the origin of this relation and the role that black holes play in the formation of galaxies are still mysteries.