Profiles of the absorbers along the QSO1 sight-line at the H I Lyα, N V, Si II, C II, and C IV lines. The black histograms show the continuum normalized data, while the orange lines are the sum of all the Gaussian components of the best fit. The locations of the absorbers considered in this analysis are highlighted with vertical dashed lines, that is, ABS1 (magenta), ABS2 (lime), and ABS3 (gray). The zero velocity is set to the redshift of the C IV strongest component. Table 2 gives all the fit parameters. For ABS1, we exclude the best fit solution for N_HI (orange) following physical arguments (Sect. 6). We thus show the two extreme alternative fits with N_HI and b values that are favored by the current data, that is, b = 100 km s⁻¹, log(N_HI/cm⁻²) = 17 as a dashed-dotted blue line, and b = 200 km s⁻¹, log(N_HI/cm⁻²) = 15 as a dotted green curve.