The origin of magnetic fields in galaxy clusters

By P. C. Tribble


It is proposed that the magnetic fields in clusters of galaxies originated in radio galaxies and have been dispersed throughout the cluster and mixed in with the thermal plasma by cluster mergers. Integrating over the radio luminosity function and the age of the universe gives an accumulated energy density in radio source remnants of 10^48 J Mpc^-3 at the present day. As the majority of powerful radio sources were in clusters or in smaller structures that were later incorporated into rich galaxy clusters, the majority of this magnetic energy is now incorporated into the intracluster medium. The energy available is 10^54 J per cluster, which is more than adequate to give fields of microGauss strength. Most of the magnetic energy was generated at high redshifts so that the magnetic fields in clusters at redshifts of order unity should have built up to almost their present strength.

Key words: magnetic fields -- galaxies: clustering -- radio continuum: galaxies Contents:

The cluster radio source population
The magnetic energy content of radio sources
Integrating over the Radio Luminosity Function
The energy per cluster
Dispersing the field
Peter Tribble,