Lyman-α spectrum of the LAB compared to the best-fit models that assume different systemic redshifts for the emitting source. The models are described in the text and their best-fit parameters are listed in Table 2. The best description of the observed Lyman-α spectrum is given by models 1–3, suggesting that the emission is produced by photoionization either from SMGs C14 or C17, or from the protocluster core.