Histogram of all map pixel temperature values across all feeds and frequencies, divided by their white noise uncertainty. The three fields are shown separately, before and after application of the map PCA filter. A normal distribution is shown in black; a completely white noise map will trace this distribution. All three fields show excess high-significance pixels before the map PCA. After the filter, all three fields fall slightly below the normal distribution on the wings, because of the slight over-subtraction of noise at various stages in the pipeline.