DR. VIRAL PAREKH

In recent years, multiwavelength observations have shown the presence of substructures related to merging events in a high fraction of galaxy clusters. Clusters can be grouped roughly into two categories - relaxed and non-relaxed – and a proper characterization of the dynamical state of these systems is of crucial importance both for astrophysical and cosmological studies. In this PhD work, we investigated the use of a number of morphological parameters (Gini, M20, Concentration, Asymmetry, Smoothness, Ellipticity and Gini of the second order moment) introduced to classify clusters automatically as relaxed or dynamically disturbed systems. Initially, we tested these parameters on the simple beta model simulations. We then applied our method to a sample of clusters at different redshifts extracted from the Chandra archive, and we investigated possible correlations between morphological parameters and other X-ray gas properties. We conclude that a combination of the adopted parameters is a useful tool to properly characterise the X-ray cluster morphology. We also applied our morphology parameters to thermodynamic maps of X-ray clusters to investigate their morphology and dynamical states. We also estimate the X-ray cluster morphological parameters in the case of radio loud (or halo) clusters. In excellent agreement with previous analyses, we confirm that diffuse intra-cluster radio sources are associated with major mergers.