Cosmic evolution of radio-AGN feedback: confronting models with data

Abstract

Radio-mode feedback is a key ingredient in galaxy formation and evolution models, required to reproduce the observed properties of massive galaxies in the local Universe. We study the cosmic evolution of radio-AGN feedback out to $z\sim 2.5$ using a sample of 9485 radio-excess AGN. We combine the evolving radio luminosity functions with a radio luminosity scaling relationship to estimate AGN jet kinetic powers and derive the cosmic evolution of the kinetic luminosity density, $\hat{I}{\text{c◯}}_{\mathrm{kin}}$ (i.e. the volume-averaged heating output). Compared to all radio-AGN, low-excitation radio galaxies (LERGs) dominate the feedback activity out to $z\sim 2.5$, with both these populations showing a constant heating output of $\hat{I}{\text{c◯}}_{\mathrm{kin}}\approx 4-5\times 10^{32}\mathrm{W}\mathrm{Mp}{\mathrm{c}}^{-3}$ across $0.5<z<2.5$. We compare our observations to predictions from semi-analytical and hydrodynamical simulations, which broadly match the observed evolution in $\hat{I}{\text{c◯}}_{\mathrm{kin}}$, although their absolute normalisation varies. Comparison to the Semi-Analytic Galaxy Evolution (SAGE) model suggests that radio-AGN may provide sufficient heating to offset radiative cooling losses, providing evidence for a self-regulated AGN feedback cycle. We integrate the kinetic luminosity density across cosmic time to obtain the kinetic energy density output from AGN jets throughout cosmic history to be $\sim 10^{50}\mathrm{J}\mathrm{Mp}{\mathrm{c}}^{-3}$. Compared to AGN winds, the kinetic energy density from AGN jets dominates the energy budget at $z\lesssim 2$; this suggests that AGN jets play an important role in AGN feedback across most of cosmic history.

15 pages, 6 figures, accepted for publication in MNRAS