Lyman-alpha emitters (LAEs) show a rich variety of spectral shapes due to the emission line’s resonant nature and typically high optical depths. While there is a large body of literature exploring how small-scale density and velocity distributions can explain this variety of features in spectra, the intergalactic medium (IGM) has often been neglecting as a contributing factor for such features.
Above sketch helps visualizing how the IGM density and velocity structure along a line-of-sight give rise to an attenuation profile possibly shaping the arising spectrum.