Searching for USSRHs in low mass merging clusters with LOFAR and the uGMRT
Virginia Cuciti (University of Hamburg)
Tuesday 26/03/2019 @ 14:00, Sala IV piano Battiferro
Radio observations reveal the presence of Mpc scale synchrotron diffuse emission in a fraction of merging galaxy clusters. In the current scenario, these sources, called radio halos, form when merger-driven turbulence re-accelerates particles in the ICM. A fundamental prediction of theoretical models is the existence of Ultra Steep Spectrum Radio Halos (USSRHs), associated with less massive clusters and/or less energetic merger events. We selected 75 clusters with M>6e14 Msun and z=0.08-0.33 from the Planck SZ catalogue and observed them with the GMRT at 610 MHz and the JVLA at 1.4 GHz to search for cluster-scale emission. We used this complete mass-selected sample of clusters to study the occurrence of radio halos as a function of the cluster mass and dynamics. The new generation of low-frequency radio telescopes, such as LOFAR and the uGMRT allows us to extend these studies to an unexplored range of frequencies where the bulk of USSRHs is expected to be discovered. In this context, we selected the low-mass merging clusters of our sample and we observed them at low frequency (<500 MHz) with LOFAR and the uGMRT. These clusters are the best candidates to host USSRHs. In this talk I will present preliminary results from these observations and I will outline the expected outcome of these low frequency studies. With these observations we will carry out a systematic search of USSRHs in galaxy clusters and we will be able to perform the first statistical study of these objects in mass-selected clusters.