On the connection between giant radio halos and cluster mergers
  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 "relaxed", with only a couple
of exceptions where a disturbed cluster does not exhibit a halo.
