Comparison of the observational dataset (black points) with the 2D probability histogram of N_H and N(CH⁺) predicted by the fiducial simulation (colored histogram) after application of the chemical solver and the lines of sight reconstruction algorithm. The observational dataset include detections (open circles) and nondetections (filled triangles) of CH⁺. The color-coding indicates the fraction of lines of sight (in logarithmic scale) contained in each bin. Two cases are shown: the chemical solver computes the abundance of H₂ at equilibrium (top panel) or uses the out-of-equilibrium abundance of H₂ calculated during the simulation (bottom panel).