Non-thermal phenomena in galaxy clusters: cosmological relevance

The emission spectrum of galaxy cluster observed from radio to gamma-rays indicates that the Intra Cluster Medium (ICM) is stratified by a set of different electron populations, which produce thermal and non-thermal phenomena. We analyze here a specific aspect of the presence of such non-thermal phenomena: the Sunyaev-Zel'dovich effect (SZE) generated by the population of relativistic electrons which are responsible for the diffuse radio halo emission observed in many galaxy clusters. We discuss briefly theoretical predictions and detectability strategies for the non-thermal SZE as well as the relevance of the non-thermal SZE for the determination of H₀.