Observations of the Galaxy Cluster MACS J1752.0+4440 with the Sardinia Radio Telescope

Radio relics are highly polarized, diffuse synchrotron sources typically found in the outskirts of galaxy clusters, where they trace shock waves in the intracluster medium (ICM) generated by cluster mergers. They represent a non-thermal component of the ICM: cosmic-ray electrons re-accelerated to relativistic energies emit synchrotron radiation in the presence of the cluster’s magnetic field. The physical mechanisms behind this emission remain poorly understood. This thesis presents an analysis of MACS J1752.0+4440, a galaxy cluster hosting a remarkable double radio relic system, with components located to the NE and SW of the cluster center. The study is based on new observations with the Sardinia Radio Telescope (SRT) at 18.6 GHz, complemented by archival JVLA data at 1.6 GHz. This is only the third study of a relic system at frequencies up to ∼20 GHz, increasing the current high-frequency sample by 50%. Expanding this sample is essential for constraining relic spectra and testing particle acceleration models in the ICM. The integrated spectrum follows a power law consistent with diffusive shock acceleration (DSA), with spectral indices of 1.24 ± 0.03 (NE) and 1.17 ± 0.03 (SW). Thanks to the reduced Faraday depolarization at ∼19 GHz, it was possible to probe the intrinsic polarization of the northern relic, finding an average fractional polarization of 33 ± 4%, with peaks of 60% in the outer regions. JVLA RM synthesis confirms high polarization levels, with averages of 35 ± 3% (NE) and 41 ± 4% (SW). The SRT data also reveal, for the first time, the Sunyaev–Zel’dovich effect at ∼19 GHz in this cluster. A Bayesian analysis yields a Compton-y parameter of order 10⁻⁵. Combining the SZ-derived density profile with RM measurements gives an average line-of-sight magnetic field strength of ∼ 2 μG in the relics. This result opens the path to follow-up SZ observations at higher frequencies, for example with the MISTRAL receiver, and highlights the potential of combining radio polarimetry with SZ measurements to jointly probe the non-thermal and thermal components of the ICM, providing a key precursor to future SKA-Mid multifrequency studies.