Synchrotron Intensity Gradient Revealing Magnetic Fields in Galaxy Clusters

Abstract: Magnetic fields and their dynamical interplay with matter in galaxy clusters contribute to the physical properties and evolution of the intracluster medium. However, the current understanding of the origin and properties of cluster magnetic fields is still limited by observational challenges. In this article, we map the magnetic fields at hundreds-kpc scales of five clusters RXC J1314.4 -2515, Abell 2345, Abell 3376, MCXC J0352.4 -7401, and El Gordo using the innovative synchrotron intensity gradient technique in conjunction with high-resolution radio observations from JVLA and MeerKAT. We demonstrate that magnetic field orientation of radio relics derived from synchrotron intensity gradients is in very good agreement with that obtained with synchrotron polarization. Most important, synchrotron intensity gradients is not limited by Faraday depolarization in the cluster central regions and allows us to map magnetic fields in the radio halos of RXC J1314.4 -2515 and El Gordo. We find that magnetic fields in radio halos exihibit a preferential direction along the major merger axis and show turbulent structures at higher angular resolution. Results are consistent with expectations from numerical simulations which predict turbulent magnetic fields in cluster mergers that are stirred and amplified by matter motions.