Abstract By analyzing Chandra X-ray data of a sample of 21 galaxy groups and 19 galaxy clusters, we find that in 31 sample systems there exists a significant central (R ≤10 h-171 kpc) gas entropy excess (∆K0 ), which corresponds to ≃ 0.1 - 0.5 keV per gas particle, beyond the power-law model that best fits the radial entropy profile of the outer regions. We also find a distinct correlation between the central entropy excess ∆K0 and K-band luminosity LK of the central dominating galaxies (CDGs), which is scaled as ∆K0 ∝ L1.6±0.4K, where LK is tightly associated with the mass of the supermassive black hole hosted in the CDG. In fact, if an effective mass-to-energy conversion- efficiency of 0.02 is assumed for the accretion process, the cumulative AGN feedback EAGNfeedback≃ηMBHc2 yields an extra heating of ≃0.5 - 17.0 keV per particle, which is sufficient to explain the central entropy excess. In most cases, the AGN contribution can compensate the radiative loss of the X-ray gas within the cooling radius ( ≃0.002 - 2.2 keV per particle), and apparently exceeds the energy required to cause the scaling relations to deviate from the self-similar predictions ( ≃0.2 - 1.0 keV per particle). In contrast to the AGN feedback, the extra heating provided by supernova explosions accounts for ≃0.01 - 0.08 keV per particle in groups and is almost negligible in clusters. Therefore, the observed correlation between ∆K0 and LK can be considered as direct evidence for AGN feedback in galaxy groups and clusters.

Keywords galaxies: active — galaxies: clusters: general — X-rays: galaxies: clus- ters — (galaxies:) intergalactic medium

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