  We report the results of our study of fractional entropy enhancement in the
intra-cluster medium (ICM) of the clusters from the representative XMM-Newton
cluster structure survey (REXCESS). We compare the observed entropy profile of
these clusters with that expected for the ICM without any feedback, as well as
with the introduction of preheating and entropy change due to gas cooling. We
make the first estimate of the total, as well as radial, non-gravitational
energy deposition up to r500 for a large, nearly flux-limited, sample of
clusters. We find that the total energy deposition corresponding to the entropy
enhancement is proportional to the cluster temperature (and hence mass), and
that the energy deposition per particle as a function of gas mass shows a
similar profile in all clusters, with its being more pronounced in the central
region than in the outer region. Our results support models of entropy
enhancement through AGN feedback.
