Effect of different parameters of the modeling on the residual fluxes. The y-axes display differences of residual fluxes between two setups. The dots are the median of the differences in a given bin of residual flux, and the bars show the 10th and 90th percentiles. The numbers indicate how many spectra are in the corresponding bin of residual flux. Left panel: effects of carbon density, which is divided or multiplied by two. Middle panel: effect of UVB radiation for ionizing photons instead of the radiation field from the simulation. Right panel: effects of turbulent velocity. Turbulent velocities are varied between 0 and 40 km s⁻¹.