Structure and evolution of magnetized clusters:: entropy profiles, S-T and LX-T relations

We study the impact of an intracluster magnetic field on the main structural properties of clusters and groups of galaxies: the radial density and entropy profiles, the entropy - temperature relation and the X-ray luminosity - temperature relation for groups and clusters of galaxies. To this aim, we develop a description of the intra-cluster gas based on the Hydrostatic Equilibrium condition and on the Magnetic Virial Theorem in the presence of a radial distribution of the magnetic field B(r) = B*(rho(g)(r))(alpha) with alpha approximate to 0.9, as the one indicated by observations and numerical simulation. Our analysis shows that such a description is able to provide, at once, a possible explanation of three problematic aspects of the cluster structure: i) the flattening of the entropy profile in the cluster center; ii) the flatness of the S - T relation; iii) the increasing steepening of the L-X - T relation from the cluster scale towards the group scales. The available entropy and X-ray luminosity data indicate that an increase of the magnetic field B* similar to T-0.5 +/- 0.1 is required to reproduce at the same time both the S - T and the LX - T relations. It follows that a consistent description of the magnetized ICM can provide a simple explanation of several (or of all) of these still open problems, and thus weakens the need for the inclusion of other non-gravitational effects which have been proposed so far for the explanation of some of these features. This (initial, but not conclusive) analysis can be regarded as a starting point for a more refined analytical exploration of the physics of the magnetized intra-cluster medium, and it provides testable predictions that can be proven or disproven with the next coming sensitive observations of groups and clusters in the X-ray band and in the radio frequency band.