Global Preventive Feedback of Powerful Radio Jets on Galaxy Formation

TL;DR

Giant radio lobes from massive galaxies exert magnetic pressure that hinders gas accretion in nearby halos, significantly impacting galaxy formation and star formation rates since redshift 2, especially in dense environments.

Contribution

This study provides observationally grounded evidence that radio jet feedback influences galaxy formation by magnetic pressure, a factor often neglected in simulations.

Findings

Halos up to 10^{11-12} Msun are hindered by radio feedback at z=2.

Radio feedback may explain the decline in star formation since z=2-3.

The flattening of the UV luminosity function around z~2 is linked to this feedback.

Abstract

Firmly anchored on observational data, giant radio lobes from massive galaxies hosting supermassive black holes can exert a major negative feedback effect, by endowing the intergalactic gas with significant magnetic pressure hence retarding or preventing gas accretion onto less massive halos in the vicinity. Since massive galaxies that are largely responsible for producing the giant radio lobes, this effect is expected to be stronger in more overdense large-scale environments, such as proto-clusters, than in underdense regions, such as voids. We show that by redshift $z=2$ halos with masses up to $(10^{11-12}, 10^{12-13})\msun$ are significantly hindered from accreting gas due to this effect for radio bubble volume filling fraction of $(1.0, 0.2)$, respectively. Since the vast majority of the stars in the universe at $z<2-3$ form precisely in those halos, this negative feedback process is likely one major culprit for causing the global downturn in star formation in the universe since. It also provides a natural explanation for the rather sudden flattening of the slope of the galaxy rest-frame UV luminosity function around $z\sim 2$. A cross-correlation between proto-clusters and Faraday rotation measures may test the predicted magnetic field. Inclusion of this external feedback process in the next generation of cosmological simulations may be imperative.