Where the wild baryons are: the outskirts of galaxy clusters

I present new results on the physical properties of the outer regions of galaxy clusters as seen in numerical simulations and X-ray data. I discuss our studies on the average properties of, and the level of clumpiness and scatter present in, the gas density and pressure profiles of massive halos extracted from cosmological hydrodynamical simulations. I describe the observational constraints on the gas density profile at R200 as obtained locally with ROSAT-PSPC and at intermediate redshift with Chandra exposures. I will illustrate a new generalized form of the universal temperature profile and how the distribution of the metals in the ICM depends upon the cluster radius and redshift.