An MHD GADGET for cosmological simulations

Various radio observations have shown that the hot atmospheres of galaxy clusters are magnetized. However, our understanding of the origin of these magnetic fields, their implications on structure formation and their interplay with the dynamics of the cluster atmosphere, especially in the centres of galaxy clusters, is still very limited. In preparation for the upcoming new generation of radio telescopes (like Expanded Very Large Array, Low Wavelength Array, Low Frequency Array and Square Kilometer Array), a huge effort is being made to learn more about cosmological magnetic fields from the observational perspective. Here we present the implementation of magnetohydrodynamics (MHD) in the cosmological smoothed particle hydrodynamics (SPH) code GADGET. We discuss the details of the implementation and various schemes to suppress numerical instabilities as well as regularization schemes, in the context of cosmological simulations. The performance of the SPH-MHD code is demonstrated in various one-and two-dimensional test problems, which we performed with a fully, three-dimensional set-up to test the code under realistic circumstances. Comparing solutions obtained using ATHENA, we find excellent agreement with our SPH-MHD implementation. Finally, we apply our SPH-MHD implementation to galaxy cluster formation within a large, cosmological box. Performing a resolution study we demonstrate the robustness of the predicted shape of the magnetic field profiles in galaxy clusters, which is in good agreement with previous studies.