Heating groups and clusters of galaxies: The role of AGN jets

¹ Dipartimento di Fisica Generale, Universitá degli Studi di Torino, Torino, Italy e-mail: zanni@ph.unito.it
² INAF - Osservatorio Astronomico di Torino, Pino Torinese, Italy

Received: 14 May 2004
Accepted: 8 September 2004

Abstract

X-ray observations of groups and clusters of galaxies show that the Intra-Cluster Medium (ICM) in their cores is hotter than expected from cosmological numerical simulations of cluster formation which include star formation, radiative cooling and SN feedback. We investigate the effect of the injection of supersonic AGN jets into the ICM using axisymmetric hydrodynamical numerical simulations. A simple model for the ICM, describing the radial properties of gas and the gravitational potential in cosmological N-Body+SPH simulations of one cluster and three groups of galaxies at redshift , is obtained and used to set the environment in which the jets are injected. We varied the kinetic power of the jet and the emission-weighted X-ray temperature of the ICM. The jets transfer their energy to the ICM mainly by the effects of their terminal shocks. A high fraction of the injected energy can be deposited through irreversible processes in the cluster gas, up to 75% in our simulations. We show how one single, powerful jet can reconcile the predicted X-Ray properties of small groups, e.g. the  relation, with observations. We argue that the interaction between AGN jets and galaxy groups and cluster atmospheres is a viable feedback mechanism.