Cosmic Rays & Magnetic Fields
The complexity of non-thermal radio sources stems from the mechanism that emits radio waves in these objects: The detected synchrotron radiation proofs the existence of electrons near the speed of light (cosmic rays) spiraling around a magnetic field a million times weaker than the field of the earth.
Cartoon showing Synchrotron radiation from a single relativistic electron. The particle emits light in a cone through an effect called relativistic beaming. (Source)
This of course raises the question where the magnetic field and the cosmic rays come from. Magnetic fields cannot be easily created, because the Universe is neutral on large scales. They can only be amplified by motions of Baryonic matter during structure formation.
Cosmic rays are surely created inside radio galaxies and injected through their jets. But they lose their energy too quickly to create objects much larger than their host galaxy. The puzzle how radio haloes larger than 100 galaxies can exist has been debated for decades in the community.
Today, some scientists believe that galaxies act as the origin source of magnetic fields and cosmic rays. Shocks and turbulence during cluster collision only re-energize a hidden and less energetic population of these particles to make radio relics and radio haloes. They complex interplay of injection, re-acceleration and cooling is the main subject of our simulations.