Histograms of excess significance for WISE12 (top left), WISE22 (top right), MIPS24 (bottom left), and MIPS70 (bottom right), together with their best-fit Gaussian noise distribution (red dashed curve). The mean (μ) and standard deviation (σ) of the noise distributions are also plotted respectively as red vertical and horizontal lines. Significance values lower than − 4 and higher than 8 are not displayed for the sake of clarity.