Constraining the magnetic field in the galaxy cluster Abell 2142 using MeerKAT L-band polarisation data

Origins of magnetic fields in galaxy clusters and their level of amplification are still debated, because constraints are available for only a few clusters. In this work, we use new MeerKAT data in polarisation to study the magnetic field intensity and profile in Abell 2142, a massive warm-cool-core cluster located at z = 0.0894. We present the first high-sensitivity L-band observations in polarisation and analyse the emission from background and cluster radio galaxies. We apply the RM synthesis technique to reconstruct the Faraday dispersion function cubes, from which we can study the magnetic field in the cluster. We find that the average RM modulus, |⟨RM⟩|, and the RM dispersion, σRM, decrease as a function of the projected distance from the cluster center, suggesting that the magnetic field becomes less intense towards larger distances, whereas the fractional polarisation radial profile indicates that radio galaxies near the cluster center suffer higher depolarisation than peripheral ones. Our new results are in line with outcomes obtained in other clusters. We combine simulations of random seed 3D magnetic fields with a model of the gas density distribution in order to create mock RM maps. The statistical comparison between the simulated maps and the observations allows us to constrain the parameters of the magnetic field model and define the best-fit magnetic field profile. Assuming that the magnetic field energy scales with the gas thermal energy, we find that a magnetic field tangled on scales between 7 and 470 kpc, with a peak in spectrum at ∼ 199 kpc and a mean central strength of 8.9 ± 3.2 μG, is the best-fit to our data. Future perspectives include the exploration of intermediate spatial scales with the same or higher/lower normalisations and of the dynamical state of the cluster. From our analysis, the average central magnetic field intensity does not allow us to rule out a potential hadronic origin of the radio mini-halo in Abell 2142.