Left: Continuum-normalized spectrum near the rest wavelength of Hα. Before the continuum normalization, the fit emission feature (Fig. C.2) was subtracted. The dashed line shows a Gaussian fit to the data. The fitting procedure yields an equivalent width of EW = 8.4 ± 2.5 km s⁻¹ and central velocity of v₀ = −37 ± 13 km s⁻¹. Middle and right: Curves of growth for Hα. Middle: Evolution of the equivalent width as a function of optical depth. Right: Similar to middle panel, but as a function of column density. The dotted horizontal line indicates the measured equivalent width from the left panel. The vertical dashed line indicates the optical depth and column density inferred from the photoionization model.