Lyα SB map showing a counterpart pair of halos in the TNG300 simulation projected on the xy plane. The Lyα SB is predicted by the model in Liu et al. (2025). The blue circles show the virial radii of the two halos. The three regions marked by solid rectangles are positioned mimicking regions taken between the two pairs of main and satellite LANs as shown in Fig. 10. The larger region marked by the dashed green rectangle encompasses the whole Lyα filament between the two halos.