Origin of cluster cosmic-ray electrons

Determine the origin of the cosmic-ray electron population responsible for the diffuse synchrotron radio emission observed in galaxy clusters, identifying the dominant injection and/or acceleration mechanisms that produce these relativistic electrons.

Background

The paper reviews that diffuse cluster radio emission is produced by relativistic electrons radiating in microgauss magnetic fields, but emphasizes that the provenance of these electrons is not established. Thermal electrons often lack sufficient energy to explain observations, motivating scenarios involving re-acceleration or non-thermal injection.

Candidate sources discussed include acceleration at shocks, merger-driven turbulence, sloshing motions, hadronic (secondary) production, and injection by AGN jets and lobes. The uncertainty in the dominant pathway for producing the required cosmic-ray electrons is a central motivation for the simulation paper.