Spherically averaged profile of the coupling coefficient for Lyα pumping x_α at z = 13.42 around the first light source in the 100  h^-1 Mpc simulation. The correct profile is represented by the thick solid line, while the other two neglect backreaction (dashed line) or radiative transfer for the higher-order Lyman-series lines (dotted line). As expected, we observe steep decreases in the value of the profile at radii corresponding to the predicted Lyγ, Lyδ and Lyϵ horizons (shown by arrows).