The environments of the radio galaxy population in SIMBA

Abstract

We investigate the environmental properties of the radio galaxy population using the S cosmological hydrodynamic simulation. We identify centrals and satellites from a population of high and low excitation radio galaxies (HERGs and LERGs) in S, and study their global properties. We find that ∼20% of radio galaxies are satellites and that there are insignificant differences in the global properties of LERGs based on its central/satellite classification. Satellite HERGs display lower values of star formation, 1.4GHz radio luminosity, and Eddington fraction. We further investigate the environments of radio galaxies and sho that HERGs typically live in underdense environments, similar to star-forming galaxies. The environments of high-mass LERGs are similar to non-radio galaxies, but low-mass LERGs live in underdense environments similar to HERGs. At all black hole masses, LERGs live in environments similar to that of quenched and normal galaxies while HERGs live in environments similar to that of star-forming galaxies. The richness of a LERG's environment decreases with increasing Eddington fraction, and the environments of all radio galaxies do not depend on radio luminosity for P 1.4GHz < 10 24 W Hz −1 . Complementing these results, we find that LERGs cluster on the same scale as the total galaxy population while HERGs are unlikely to be found within the same dark matter halo. Finally, we show that there is no environmental preference for radio galaxies at z=2. S predicts that with more sensitive surveys, we will find populations of radio galaxies in environments much similar to the total galaxy population.