Effects of line profiles deviating from a typically Gaussian shape. (a) υ_G − υ₀ as a function of optical depth and velocity dispersion, where υ_G and υ₀ are the velocity centroid derived from the Gaussian fitting and the intrinsic velocity centroid. (b) σ_G/σ₀ as a function of optical depth and velocity dispersion, where σ_G and σ₀ are the velocity dispersion derived from the Gaussian fitting and the intrinsic velocity dispersion.