[CII] emission surface-brightness map for one of the selected TNG50 galaxies at z = 5, assuming C⁺ abundances with UVB and local young stars as ionization sources. Left: the map is presented at the full-resolution of the simulation. Right: the map has been convolved with the average ALMA beam of the G20 observations (bottom left corner). The white contour represents the average 2σ level of the observations (0.08 Jy km s⁻¹ beam⁻¹).