Simulated column density of neutral hydrogen, N_HI, in a simulation snapshot at z = 4.8. The same regions as in Fig. 8 are shown. Moreover, the same density thresholds used for the collisional excitation component are applied, that is only gas below half the critical self-shielding density is shown, meaning this is the column density that would correspond to a narrowband image of the low-density gas with Δλ_obs = 3.75 Å (∼1.19 h⁻¹ cMpc). Panel a: overview of part of the simulation snapshot that corresponds to region 1 in Fig. 4. This is centred on the same comoving coordinates both spatially and spectrally, but now less extended in wavelength range. This panel shows a region of 8 × 8 h⁻² cMpc² (5.2 × 5.2 arcmin²) on a pixel grid of 1024 × 1024. Panels b–d: column density maps of neutral hydrogen the size of the MUSE FOV consisting of 300 × 300 pixels. The areas covered by these maps are indicated by the black squares in the overview panel a. In the bottom left corner of each panel, two different measures of the overdensity of the region are shown (see Sect. 3.4 for more details). In panels b–d, halos with halo mass of M_h > 10^9.5 M_⊙ are shown as circles, their size indicating their projected virial radius (see Sect. 3.4). The most massive halo in each panel is annotated.