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تسجيل مستخدم جديدOn the occurrence of Radio Halos in galaxy clusters - Insight from a mass-selected sample
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Giant radio halos (RH) are diffuse Mpc-scale synchrotron sources detected in a fraction of massive and merging galaxy clusters. An unbiased study of the statistical properties of RHs is crucial to constrain their origin and evolution. We aim at investigating the occurrence of RHs and its dependence on the cluster mass in a SZ-selected sample of galaxy clusters, which is as close as possible to be a mass-selected sample. Moreover, we analyse the connection between RHs and merging clusters. We select from the Planck SZ catalogue (Planck Collaboration XXIX 2014) clusters with $Mgeq 6times10^{14} M_odot$ at z=0.08-0.33 and we search for the presence of RHs using the NVSS for z<0.2 and the GMRT RH survey (GRHS, Venturi et al. 2007, 2008) and its extension (EGRHS, Kale et al. 2013, 2015) for 0.2<z<0.33. We use archival Chandra X-ray data to derive information on the clusters dynamical status. We confirm that RH clusters are merging systems while the majority of clusters without RH are relaxed, thus supporting the idea that mergers play a fundamental role in the generation of RHs. We find evidence for an increase of the fraction of clusters with RHs with the cluster mass and this is in line with expectations derived on the basis of the turbulence re-acceleration scenario. Finally, we discuss the effect of the incompleteness of our sample on this result.
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Many galaxy clusters host Mpc scale diffuse radio sources called radio halos. Their origin is connected to the processes that lead to the formation of clusters themselves. In order to unveil this connection, statistical studies of radio halos are nec
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Radio halos are synchrotron diffuse sources at the centre of a fraction of galaxy clusters. The study of large samples of clusters with adequate radio and X-ray data is necessary to investigate the origin of radio halos and their connection with the
cluster dynamics and formation history. The aim of this paper is to compile a well-selected sample of galaxy clusters with deep radio observations to perform an unbiased statistical study of the properties of radio halos. We selected 75 clusters with M > = 6e14 Msun at z=0.08-0.33 from the Planck Sunyaev-Zeldovich catalogue. Clusters without suitable radio data were observed with the Giant Metrewave Radio Telescope (GMRT) and/or the Jansky Very Large Array (JVLA) to complete the information about the possible presence of diffuse emission. We used archival Chandra X-ray data to derive information on the clusters dynamical states. This observational campaign led to the detection of several cluster-scale diffuse radio sources and candidates that deserve future follow-up observations. Here we summarise their properties and add information resulting from our new observations. For the clusters where we did not detect any hint of diffuse emission, we derived new upper limits to their diffuse flux. We have built the largest mass-selected (> 80 per cent complete in mass) sample of galaxy clusters with deep radio observations available to date. The statistical analysis of the sample, which includes the connection between radio halos and cluster mergers, the radio power-mass correlation, and the occurrence of radio halos as a function of the cluster mass, will be presented in paper II.
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