CII/CIVW₀ line ratio as a function of the impact parameter b, and the foreground galaxy’s stellar mass and SFR. CII/CIVW₀ values were obtained considering the same set of fg–bg galaxy pairs. Average and median W₀ are shown in solid red and open blue symbols; the solid black symbols correspond to upper limits with S/N < 3. The error bars correspond to 1σ confidence intervals for average or median values based on a bootstrap analysis.