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

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, ${\mathrm{\Omega }}_{\mathrm{k}\mathrm{i}\mathrm{n}}$ (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 ${\mathrm{\Omega }}_{\mathrm{k}\mathrm{i}\mathrm{n}}\approx 4-5\times {10}^{32}\mathrm{W}\mathrm{M}\mathrm{p}{\mathrm{c}}^{-3}$ 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 ${\mathrm{\Omega }}_{\mathrm{k}\mathrm{i}\mathrm{n}}$, 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 $\sim {10}^{50}\mathrm{J}\mathrm{M}\mathrm{p}{\mathrm{c}}^{-3}$. 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.