Emergent Lyman-alpha line and IGM opacity as a function of wavelength. The solid blue line represents the normalized Lyman-α emergent profile, and the dot-dashed blue line demarcates the flux absorbed by the circumgalactic medium blueward of the circular velocity of the galaxy. The solid black line illustrates an IGM damping wing attenuation profile, taken from a random sightline at ${\overline{x}}_{\mathrm{HI}}=0.65$ and R_b = 10 cMpc (see text for details). The Lyman-alpha transmission integrated over all wavelengths for this example would be ${\mathcal{T}}_{\mathrm{EoR}}\equiv \int \text{d}\lambda J(\lambda )e^{-{\tau }_{\mathrm{EoR}}(\lambda )}=0.10$.