EW distribution of the Siii feature at 1527 Å. The thick black line histogram indicates only detections, whereas the dotted histogram includes also the limits. The red line is the best fit of the complete histogram with a lognormal distribution and the dashed blue line is a physical fit as described in Sect. 3.4. In green we show a histogram of EWs in a sample of DLA systems (see Sect. 3.3) and its lognormal fit. Similar histograms for all the lines in the sample can be found in Fig. B.1.