Left: I_R − I_X relation for the northern (turquoise) and southern (orange) parts of the halo. The upper limits (arrows) represent cells with data points below 2σ radio noise level. The horizontal black dash-dotted lines indicate the 1σ in the radio maps. The turquoise and orange dashed lines correspond to the best-fit obtained separately for the northern and southern, respectively, parts of the halo. The best-fits are reported with the corresponding 95% confidence regions. The correlation slope is indeed different for the northern and southern regions of the halo: the southern part of the halo is steeper than the northern part at all three frequencies.