Tracing the Remnants of Powerful Quasars to Probe the IGM

Abstract

Powerful quasars and radio galaxies are injecting large amounts of energy in the form of radio plasma into the inter-galactic medium (IGM). Once this nonthermal component of the IGM has radiatively cooled the remaining radio emission is difficult to detect. Two scenarios in which the fossil radio plasma can be detected and thus be used to probe the IGM are discussed: a) re-illumination of the radio emission due to the compression in large-scale shock waves, and b) inverse Compton scattered radiation of the cosmic microwave background (CMB), cosmic radio background (CRB), and the internal very low frequency synchrotron emission of the still relativistic low energy electron population. We present 3-D magneto-hydrodynamical simulations of scenario a) and compare them to existing observations. Finally, we discuss the feasibility of the detection of process b) with upcoming instruments.