SPH simulations of magnetic elds in galaxy clusters

We perform cosmological, hydrodynamic simulations of magnetic elds in galaxy clusters. The computational code combines the special-purpose hardware Grape for calculating gravitational interaction, and smooth-particle hydrodynamics for the gas component. We employ the usual MHD equations for the evolution of the magnetic eld in an ideally conducting plasma. As a rst application, we focus on the question what kind of initial magnetic elds yield nal eld conngurations within clusters which are compatible with Faraday-rotation measurements. Our main results can be summarised as follows: (i) Initial magnetic eld strengths are ampliied by approximately three orders of magnitude in cluster cores, one order of magnitude above the expectation from spherical collapse. (ii) Vastly diierent initial eld conngura-tions (homogeneous or chaotic) yield results that cannot signiicantly be distinguished. (iii) Micro-Gauss elds and Faraday-rotation observations are well reproduced in our simulations starting from initial magnetic elds of 10 ?9 G strength. Our results show that (i) shear ows in clusters are crucial for amplifying magnetic elds beyond simple compression, (ii) nal eld conngurations in clusters are dominated by the cluster collapse rather than by the initial connguration, and (iii) initial magnetic elds of order 10 ?9 G are required to match Faraday-rotation observations in real clusters.