Top: estimates for the extragalactic contribution to each source’s observed Faraday depth for the “polar caps” analysis versus Galactic latitude. Bottom: the same for a random sample drawn from the posterior PDF for the extragalactic contributions around the mean plotted in the upper panel. In both panels, the grayscale shows the density of the data points of the SIP category, i.e., with noise variance correction factors, and data points of the VIP category, i.e., without noise variance correction factors, are plotted as green +–symbols.