Adaptive narrow-band image of LAB1. The image is the result of summing only over voxels in the continuum-subtracted datacube that have a S/N >  4 in the LSDCat cross-correlated datacube. For spaxels that do not contain voxels above this threshold we simply sum over 5 Å (four datacube layers) around 4985.6 Å (=(1 + z_LAB1) × λ_Lyα). As in Fig. 4, we masked sources where the continuum subtraction with a running median filter failed. In order to further enhance low-SB Lyα features, we smoothed the final image with a σ = 0.2″ Gaussian kernel. The photometric centre and the principal axis of the blob are indicated by a cyan cross and a cyan dashed line, respectively. Previously known galaxies at z = 3.1 are indicated using the same symbols as in Fig. 1.