Upper panel: temperature asymmetry in μK, in the 70 GHz Planck band, of regions A3 and A4 compared with regions A1 and A2 in four annuli around M 33 (light brown histograms). The dark brown histograms depict the mean ΔT value of the 360 control fields with the corresponding standard error of the mean. Bottom panel: cumulative distribution of the 360 control field temperature asymmetry in the four regions in the upper panel. The vertical lines show the temperature asymmetry value toward M 33 for each considered region.