Jet-induced star formation in gas-rich galaxies

TL;DR

This study uses high-resolution simulations to show that AGN jets can trigger star formation in gas-rich high-redshift galaxies by compressing the interstellar medium, leading to significant new stellar populations.

Contribution

First detailed simulation of jet-induced star formation in a high-redshift galaxy's gas-rich disk, revealing positive feedback effects of AGN jets.

Findings

Jet activity creates a blast wave that compresses and cools the ISM.

Formation of a ring- or disc-shaped young star population.

Up to 10^10 solar masses of stars formed due to jet activity.

Abstract

Feedback from active galactic nuclei (AGN) has become a major component in simulations of galaxy evolution, in particular for massive galaxies. AGN jets have been shown to provide a large amount of energy and are capable of quenching cooling flows. Their impact on the host galaxy, however, is still not understood. Subgrid models of AGN activity in a galaxy evolution context so far have been mostly focused on the quenching of star formation. To shed more light on the actual physics of the "radio mode" part of AGN activity, we have performed simulations of the interaction of a powerful AGN jet with the massive gaseous disc (10^11 solar masses) of a high-redshift galaxy. We spatially resolve both the jet and the clumpy, multi-phase interstellar medium (ISM) and include an explicit star formation model in the simulation. Following the system over more than 10^7 years, we find that the jet activity excavates the central region, but overall causes a significant change to the shape of the density probability distribution function and hence the star formation rate due to the formation of a blast wave with strong compression and cooling in the ISM. This results in a ring- or disc-shaped population of young stars. At later times, the increase in star formation rate also occurs in the disc regions further out since the jet cocoon pressurizes the ISM. The total mass of the additionally formed stars may be up to 10^10 solar masses for one duty cycle. We discuss the details of this jet-induced star formation (positive feedback) and its potential consequences for galaxy evolution and observable signatures.