Color-coded distribution of the cluster ionizing flux (Q(H⁰)) and  for the low- and high-mass cluster set. The shaded contour represents the low-mass cluster set, the solid-line contour the high-mass cluster set. A strong correlation between both quantities is seen for the low-mass cluster set case. The same corelation can be seen in the lower part of the distribution of the high mass set, and is lost in the upper part, where the distribution tends to the asymptotic . The insets show the histograms of the  distribution for two values of Q(H⁰). The range in Q(H⁰) for those histograms are marked with vertical dotted lines. As a reference, we also plot the  reference scale (line with symbols).