Magnetic energy injected by a stellar population of mass M_cluster over SN energy of the same population. The latter is calculated as 10⁵¹ erg times the total number of massive stars. The shaded area shows the range of values assuming different magnetic field distributions for the stars. The top panel assumes bimodal magnetic field distributions (top panel of Fig. 1) and the bottom one assumed Gaussian ones (bottom panel of Fig. 1). The two lines in each panel show results for different IMFs.