Verification of match probabilities. The top panels indicate the distribution of match probabilities (left/right) for associated 4FGL sources. The blue (orange) histograms indicate the match probabilities assigned to sources known to be the correct (incorrect) counterparts of the given 4FGL source, with the black dashed line indicating the sum of the two distributions. The lower panels show calibration curves for the two classes, plotting the observed fraction of correctly detected counterparts ƒ_det, for sources binned by predicted match probability . The red line indicates the 1 : 1 relation expected for an ideal, unbiased classifier.