Did Radio Galaxies Play a Major Role in the Evolution of the Universe?

Abstract

During the `quasar era' at z ~ 2 - 3, radio galaxies had a much higher co-moving density; however, such sources are only detectable for small fractions of their active lifetimes, thanks to expansion losses and inverse Compton losses against the much more intense cosmic microwave background. Combining models for the evolution of the size and luminosity of double radio sources with cosmological simulations of the cosmic web of baryonic material, we find that during the quasar era a large volume fraction of this web was pervaded by the lobes associated with generations of double radio sources. These overpressured, expanding radio lobes could compress gas clouds in the space engulfed by them and trigger global starburst activity. In the process, radio galaxies could have also seeded the IGM with an average magnetic field ~ 10-8G; moreover, they could have played an important role in the widespread metal pollution of the IGM.