Cold fronts in galaxy clusters

Abstract

Context. Cold fronts have been observed in several galaxy clusters. Understanding their nature and origin is extremely important for investigating the internal dynamics of clusters. Aims. To gain insight into the nature of these features, we carry out a statistical investigation of their occurrence in a sample of galaxy clusters observed with XMM-Newton and correlate this occurrence with different cluster properties. Methods. We selected a sample of 45 clusters starting from the B55 flux limited sample (Edge et al. 1990, MNRAS, 245, 559) and performed a systematic search for cold fronts. Results. We find that a large fraction of clusters host at least one cold front. Cold fronts are easily detected in all systems that are manifestly undergoing a merger event in the plane of the sky, while the presence of these features in the remaining clusters is related to a steep entropy gradient, in agreement with theoretical expectations. Assuming that cold fronts in cool core clusters are triggered by minor merger events, we estimate a minimum of 1/3 merging events per halo per Gyr.

Dark matter distribution in X-ray luminous galaxy clusters with Emergent Gravity

“…MDM/Mgas ∼ 4 − 7) and the rest in stars (few per cent; see e.g. Gonzalez et al 2013). Although an intriguing and plausible explanation to the observed gravitational effects induced from galaxy clusters, the still unknown nature of the dark matter invites to consider alternative scenarios.…”

Testing Secondary Models for the Origin of Radio Mini-Halos in Galaxy Clusters

“…Most cool-core clusters also possess spiral-shaped cold fronts (Ghizzardi et al 2010), which are believed to be the product of the central cold gas "sloshing" in the cluster potential minimum due to interactions with subclusters. A number of simulation works have investigated the importance of this phenomenon (e.g., Ascasibar & Markevitch 2006;ZuHone et al 2010;Roediger et al 2011).…”

Minor Merger-Induced Cold Fronts in Abell 2142 and RXJ1720.1+2638

“…This remnant core scenario is observed in a number of clusters, e.g., 1ES0657-558 (otherwise known as the Bullet cluster; Markevitch et al 2002), Abell 1758 , Abell 115 (Gutierrez & Krawczynski 2005), Abell 2744 Owers et al 2011), Abell 2146 (Russell et al 2010), and probably Abell 2069 (Owers et al 2009b). As the number of clusters observed by Chandra increased, two things emerged: (1) the remnant core scenario cannot explain the majority of the observed cold fronts, and (2) there is a clear dichotomy when considering the X-ray morphology of clusters hosting cold fronts (Markevitch & Vikhlinin 2007;Owers et al 2009b;Ghizzardi et al 2010). One subset of cold front clusters exhibits clearly disturbed X-ray morphologies, while the second subset has cool cores and appears relaxed at large radii.…”