The posterior distribution for S II is plotted with two-dimensional histograms comparing each pair of free parameters. The contours represent the confidence levels of 1σ, 2σ, etc. N _{S II} is the logarithmic ionic column density in cm⁻², z _v is the velocity shift of each component in km s⁻¹, and b is the velocity broadening in km s⁻¹. The inset displays the identical posterior distribution, where the velocity-broadening parameter is fixed to the fitted value.