Context. Cold fronts have been observed in several galaxyclusters. Understanding their nature and origin is extremely importantfor investigating the internal dynamics of clusters. Aims. To gain insight into the nature of these features, wecarry out a statistical investigation of their occurrence in a sampleof galaxy clusters observed with XMM-Newton and correlate thisoccurrence with different cluster properties. Methods. We selected a sample of 45clusters starting fromthe B55 flux limited sample (Edge etal. 1990, MNRAS, 245, 559)and performed a systematic search for cold fronts. Results. We find that a large fraction of clusters host at leastone cold front. Cold fronts are easily detected in all systems that aremanifestly undergoing a merger event in the plane of the sky, while thepresence of these features in the remaining clusters is related to asteep entropy gradient, in agreement with theoretical expectations.Assuming that cold fronts in cool core clusters are triggered by minormerger events, we estimate a minimum of 1/3merging events perhalo perGyr. Key words: galaxies: clusters: general - X-rays: galaxies: clusters
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