Distribution of C IV doublet velocity (v) and absorption spread (σ_∥) by system. The blue dashed line marks the zero-point velocity, and the orange dashed line indicates the median absorption spread (⟨σ_∥⟩). The blue horizontal solid line has a size equal to the transverse velocity dispersion (σ_⊥); its blue side is arbitrarily placed at zero velocity for a visual comparison between σ_⊥ and ⟨σ_∥⟩. The data represented in this figure has not been corrected for incompleteness.