On the connection between giant radio halos and cluster mergers

Understand

The frequently observed association between giant radio halos and merging galaxy clusters has driven present theoretical models of non-thermal emission from galaxy clusters, which are based on the idea that the energy dissipated during cluster-cluster mergers could power the formation of radio halos.

• To quantitatively test the merger-halo connection we present the first statistical study based on deep radio data and X-ray observations of a complete X-ray selected sample of galaxy clusters with X-ray luminosity > 5x 10^44 erg/s and redshift 0.2<z< 0.32.
• Using several methods to characterize cluster substructures, namely the power ratios, centroid shift and X-ray brightness concentration parameter, we show that clusters with and without radio halo can be quantitatively differentiated in terms of their dynamical properties.
• In particular, we confirm that radio halos are associated to dynamically disturbed clusters and cluster without radio halo are more &#34;relaxed&#34;, with only a couple of exceptions where a disturbed cluster does not exhibit a halo.