Reviving fossil radio plasma in clusters of galaxies by adiabatic compression in environmental shock waves

By Torsten A. Ensslin Gopal-Krishna. 2000

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We give for a plasma with a history of several expansion and contraction phases an analytical model of the evolution of a contained relativistic electron population under synchrotron, inverse Compton and adiabatic energy losses or gains. This is applied to different scenarios for evolution of radio plasma inside the cocoons of radio galaxies, after the activity of the central engine has ceased. It is demonstrated that fossil radio plasma with an age of even up to 2 Gyr can be revived by compression in a shock wave of large-scale structure formation, caused during the merging events of galaxy clusters, or by the accretion onto galaxy clusters. We argue, that this is a highly plausible explanation for the observed cluster radio relics, which are the regions of diffuse radio emission found in clusters of galaxies, without any likely parent radio galaxy seen nearby. An implication of this model is the existence of a population of diffuse, ultra-steep spectrum, very low frequency radio sources located inside and possibly outside of clusters of galaxies, tracing the revival of aged fossil radio plasma by the shock waves associated with large-scale structure formation.

Subfields: Astronomy and Astrophysics, Atomic and Molecular Physics, and Optics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/d5ac0b6a5c3894da26ca5b7b2f9da8d1862452e1

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Citations in the corpus

Constraining the population of cosmic ray protons in cooling flow clusters with γ-ray and radio observations: Are radio mini-halos of hadronic origin? (2003, background): “There is also evidence that reacceleration processes acting on fossil radio plasma produces small filamentary radio relics at the cluster periphery, so-called revived radio ghosts (Enßlin & Gopal-Krishna 2001; Enßlin & Br¨uggen 2002) presumably by adiabatic compression in shock waves.”
Four Extreme Relic Radio Sources in Clusters of Galaxies (2001, methodology): “…for the production of halos and relics include the remnants of de-energised radio galaxies, adiabatic recompression of old, expanded radio lobes (Enßlin & Gopal-Krishna 2001), the turbulent wakes of galaxies that once passed through the region, reacceleration of electrons in shock fronts caused…”
Science with ASKAP (2008, background): “[90, 91, 96]), ‘fat double’ FRI tails and plumes [253], and perhaps even the Thomson scattered electrons off Dark Matter (see Section 3.”
Radio signature of cosmological structure formation shocks (2006, background): “…at the shock waves themselves (Enßlin et al. 1998; Miniati et al. 2001), or they could be old radio bubbles that are compressed by the passing shock wave and thus induced to emit observable synchrotron emission again (Enßlin & Gopal-Krishna 2001; Enßlin & Brüggen 2002; Hoeft et al. 2004).”