Application of the FDR method to the 201 identified continuum sources around M 51 with two values of the false discovery rate, α (5% and 50%). Each dot shows the p-value of a source, p_j. The sources have been sorted by increasing p-value. The FDR method finds the (last) intersection of this distribution and a line with the slope , and classifies as reliable detections all the sources located to the left of the intersection (the green points have a 5% false discovery rate).