Top: PI versus I for SNR(I) > 25. The light and dark blue symbols are data points with 1 <SNR(PI) < 3 and SNR(PI) > 3, respectively. The dots correspond to 12′′ pixels. The red solid curve shows the median log(PI) per bin of log(I). The lower and the upper dashed red lines show the 16% and 84% percentiles, respectively. The black solid line is a linear fit to the distribution for SNR(PI) > 3 and I > 150 mJy beam⁻¹ (indicated by the dotted vertical line). The value of the slope is given on the plot. The black dashed line is a linear fit to the upper 95% percentiles (see Sect. 3.3). The upper x-axis gives an estimate of the column density (see Sect. 2.3). Bottom: PF versus I. The dots, curves, and colors are the same as the upper plot for PF versus I.