Left: Lyα emission line and Lyβ absorption line in J0921+4509 (C_f(H I) = 0.761). Right: Lyα emission line and Lyβ absorption line in J1442−0209 (C_f(H I) = 0.556). The Lyα spectra have been smoothed to half the resolution of the observations and scaled down with a power law for display purposes. The presence of Lyα emission on top of the optically thick H I absorption line suggests that Lyα photons can escape at lower velocities through low-density channels. Similar plots for all the galaxies in our sample are given in Appendix C.