ON THE CONNECTION BETWEEN GIANT RADIO HALOS AND CLUSTER MERGERS

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Abstract
The frequently observed association between giant radio halos (RHs) 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 RHs. 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 ≥5 × 1044 erg s–1 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 RH can be quantitatively differentiated in terms of their dynamical properties. In particular, we confirm that RHs are associated with dynamically disturbed clusters and clusters without RH are more "relaxed," with only a couple of exceptions where a disturbed cluster does not exhibit a halo.
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