IGM transmission T_IGM for a Lyα emitting source at z = 6 for a given Lyα velocity offset Δv_Lyα (coloured according to the scale shown on the top) as a function of the size of the ionised bubble, R_ion. Results are shown both for a residual neutral fraction within the bubble scaling as x_H I ∝ r² (solid lines) and where it is constant with radius (dashed lines). Transmission curves in the top panel assume a global neutral hydrogen fraction of appropriate for the later stages of reionisation, whereas the bottom panel shows the transmission in a patchy reionisation scenario, where photons encounter gas that is still fully neutral upon exiting the ionised bubble ().