A non-ideal magnetohydrodynamic gadget: Simulating massive galaxy clusters

Magnetic fields in the intra-cluster medium (ICM) of galaxy clusters have been studied in the past through different methods. So far, our understanding of the origin of these magnetic fields, as well as their role in the process of structure formation and their interplay with the other constituents of the ICM, is still limited. In the coming years, the up-coming generation of radio telescopes is going to provide new data that will have the potential of setting constraints on the properties of magnetic fields in galaxy clusters. Here, we present zoomed-in simulations for a set of massive galaxy clusters (Mv≥ 1015h-1M⊙). This is an ideal sample to study the evolution of the magnetic field during the process of structure formation in detail. Turbulent motions of the gas within the ICM will manifest themselves in a macroscopic magnetic resistivity ηm, which has to be taken explicitly into account, especially at scales below the resolution limit. We have adapted the magnetohydrodynamic (MHD) gadget code by Dolag & Stasyszyn to include the treatment of the magnetic resistivity, and for the first time we have included non-ideal MHD equations to better follow the evolution of the magnetic field within the galaxy clusters. We investigate which value of the magnetic resistivity ηm is required to match the magnetic field profile derived from radio observations. We find that a value of ηm~ 6 × 1027cm2s-1 is necessary to recover the shape of the magnetic field profile inferred from radio observations of the Coma cluster. This value agrees well with the expected level of turbulent motions within the ICM at our resolution limit. The magnetic field profiles of the simulated clusters can be fitted by a β-model-like profile, with small dispersion of the parameters. We also find that the temperature, density and entropy profiles of the clusters depend on the magnetic resistivity constant, having flatter profiles in the inner regions when the magnetic resistivity increases. © 2011 The Authors Monthly Notices of the Royal Astronomical Society © 2011 RAS.