Lyα spectrum extracted from the CEN region with sk <  −0.5 and S/N >  3 and modelled (blue solid line) by two Gaussian components (red dotted and green dashed lines). Interestingly, the broad (∼1170 km s⁻¹) wing is blueshifted by ∼1520 km s⁻¹ from the narrow component. The grey area is not considered in the modelling as it includes a region contaminated by a sky feature. The yellow region reports the ±1σ uncertainty on the z_QSO.