Median spectra of galaxies in various halo mass ranges, normalized to the same stellar mass (10^9.5 h⁻¹ M_⊙), and including the impact of the IGM on the line. The shaded areas show the 68% PIs. Although the median flux in the line hardly rises above the continuum, prominent lines are seen for a significant fraction of the galaxies. Also shown (using the right y axis) is the median transmission of the 16 filters (yellow), and the IGM transmission 𝒯(λ) (black), with the shaded regions showing the 68% scatter.