The role of quasars in galaxy formation

TL;DR

This paper explores the potential active role of quasars and radio jets in galaxy formation by inducing star formation, challenging the traditional view that they mainly quench star formation in massive galaxies.

Contribution

It presents evidence supporting the idea that radio jets can promote star formation during galaxy formation, a novel perspective contrasting with previous assumptions of quenching effects.

Findings

Discovery of an ultra-luminous infrared galaxy triggered by a radio jet.

Observation of offset between molecular gas and quasars in several systems.

Evidence suggesting radio jets can induce star formation in galaxy formation processes.

Abstract

We discuss evidence that quasars, and more generally radio jets, may have played an active role in the formation stage of galaxies by inducing star formation, i.e. through positive feedback. This mechanism first proposed in the 70's has been considered as anecdotic until now, contrary to the opposite effect that is generally put forward, the quenching of star formation in massive galaxies to explain the galaxy bimodality, downsizing and the universal black hole mass over bulge stellar mass ratio. This suggestion is based on the recent discovery of an ultra-luminous infrared galaxies, i.e. an extreme starburst, which appears to be triggered by a radio jet from the QSO HE0450-2958 at z=0.2863, together with the finding in several systems of an offset between molecular gas and quasars, which may be explained by the positive feedback effect of radio jets on their local environment.