Mergers between galaxy clusters are the most energetic phenomena in the Universe. During these cosmic collisions, turbulence and shocks are generated into the ICM where they are believed to power Mpc-scale diffuse synchrotron sources in form of radio halos and radio relics. Nowadays, studies on non-thermal phenomena in merging galaxy clusters have been limited to a few tens of massive systems (M500 > 5-6 x 10^14 Msun), which host the most powerful halos and relics. Thanks to the all-sky surveys performed with eROSITA, LOFAR, and Planck, we will finally be in the position to extend these studies over a broad range of cluster mass and redshift and thus to unravel the origin of radio diffuse sources in the ICM.
The Planck Sunyeav Zel'dovic catalog collects a nearly mass-selected sample of galaxy clusters. We are carrying out the analysis of LOFAR observations coming from LoTSS (that is an on-going radio survey aimed at imaging the entire northern sky at 120-168 MHz) of all these systems to perform the largest statistical study ever done on non-thermal phenomena in galaxy clusters. However, many of the Planck clusters do not have X-ray information available at the moment. In this respect, the eROSITA survey will have a critical role, allowing us to understand the dynamical state of the clusters and thus to study the occurrence of diffuse radio emission in merging galaxy clusters.
In my talk, I will present the current status of the LOFAR analysis based on ~300 Planck clusters observed in the context of LoTSS. A large fraction of these systems host diffuse radio sources in the ICM, for the very first time detected in low-mass (M500 < 5 x 10^14 Msun) and high-z (z>0.6) systems. These clusters are fundamental to test the theoretical models of the formation of halos and relics. The eROSITA survey will detect these systems, which are below the sensitivity of the ROSAT All-Sky Survey, allowing us to study the interplay between thermal and non-thermal components in the ICM.