How TeV Blazars Might Rewrite the Thermal History of the Universe: A Story About Non-local AGN Feedback

Abstract: A recently discovered class of active galactic nuclei, TeV luminous blazars, constitute a small fraction of the power output of black holes. Nevertheless, there are suggestions that unlike the UV and X-ray luminosity of quasars, the very-high energy gamma-ray emission from the TeV blazars can be thermalized on cosmological scales with order unity efficiency, resulting in a dramatic heating of the low-density intergalactic medium. This occurs through virulent plasma instabilities, driven by the anisotropy of the relativistic pairs produced by the annihilation of TeV gamma rays on the extragalactic background light. Necessarily, this mechanism imparts a variety of peculiar properties to the heating, resulting in a number of robust cosmological consequence. I will discuss how this works in practice, and what observational evidence we now have that plasma instabilities may indeed be ruling the fate of the intergalactic medium.