Nicole Thomas

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-active galactic nuclei (AGN) feedback out to z ∼ 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, Ωkin (i.e. the volume-averaged heating output). Compared to all radio-AGN, low-excitation radio galaxies dominate the feedback activity out to z ∼ 2.5, with both these populations showing a constant heating output of $\Omega _{\rm {kin}} \approx (4\!-\!5) \times 10^{32}\, \rm {W\, Mpc^{-3}}$ 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 Ωkin, although their absolute normalization 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 $\sim 10^{50}\, \rm {J\, Mpc^{-3}}$. Compared to AGN winds, the kinetic energy density from AGN jets dominates the energy budget at z ≲ 2; this suggests that AGN jets play an important role in AGN feedback across most of cosmic history.