2007MNRAS.378.1565C

In this paper we derive new expected scaling relations for clusters with giant radio haloes in the framework of the re-acceleration scenario in a simplified, but physically motivated, form, namely: radio power (P_R) versus size of the radio emitting region (R_H), and P_R versus total cluster mass (M_H) contained in the emitting region and cluster velocity dispersion (σ_H) in this region.

We search for these correlations by analysing the most recent radio and X-ray data available in the literature for a well-known sample of clusters with giant radio haloes. In particular we find a good correlation between P_R and R_Hand a very tight `geometrical' scaling between M_H and R_H. From these correlations P_R is also expected to scale with M_H_ and σ_Hand this is confirmed by our analysis. We show that all the observed trends can be well reconciled with expectations in the case of a slight variation of the mean magnetic field strength in the radio halo volume with M_H. A byproduct correlation between R_H_ and σ_His also found, and can be further tested by optical studies. In addition, we find that observationally R_Hscales non-linearly with the virial radius of the host cluster, and this immediately means that the fraction of the cluster volume which is radio emitting increases with cluster mass and thus that the non-thermal component in clusters is not self-similar.