Thin projections through the center of Halo3 displaying the root mean square magnetic field strength and vorticity, respectively, at z = 3 in the non-radiative (first row) and radiative (second row) simulations. The bottom two rows show the same but at z = 0. The virial radius R₂₀₀ is indicated with a white circle. From left to right, the panels have sidelengths L = 4R₂₀₀,  2R₂₀₀,  0.5R₂₀₀ and a thickness of L/10. At z = 3, the magnetic field in the radiative simulation is nearly saturated. The BCG appears as a bright spot with a strong magnetic field. An object infalling from the left has also developed a strong magnetic field that will contribute to the cluster’s final magnetic field. By contrast, at z = 3 the magnetic field in the non-radiative simulation remains weak. The infalling object is not visible, and there is no BCG. This underscores the magnetic field growth in galaxies and its transport to the ICM via merging halos.