Median (left panel) and 3σ-clipped weighted mean (right panel) stacked spectrum for 1716 DLAs with median hydrogen column density of log(N_H I/cm⁻²) = 21.2, along with 1σ error shown in grey color. The green hatched region show the dark core of absorption trough, with optical depth (τ) > 10. The red curve shows the emergent Lyα profile, after radiative transfer of Lyα photons while considering the DLAs as expanding thin-shell geometry (see text Gurung-López et al. 2022).