Speaker
Description
Recent LOFAR observations of massive galaxy clusters revealed the presence of very extended and low brightness radio emission, named megahalo. Due to their size, megahalos could allow us to probe cluster volumes roughly 30 times larger than those covered by radio halos, opening a new window to study non-thermal components (cosmic rays and magnetic fields) and acceleration mechanisms in the peripheries of clusters. So far, megahalos have been observed by LOFAR in four massive clusters ($M>6\times10^{14} M_\odot$), although their existence still has to be confirmed with observations at other frequencies. In this talk, I will present three new candidate megahalos, including spectral index studies obtained combining data at 50 and 144 MHz. Furthermore, I will discuss the modelling of the brightness profiles of megahalos to improve our understanding on the acceleration mechanisms that might originate these sources. Finally, I will cover the analysis of LOFAR simulated observations aimed at determine the possible presence of systematic errors in the current megahalos detections.
