Zoomed-in frequency slices of the simulated population of DM halos and resulting mock observations. Left: DM halos, coloured by their halo mass. Centre: Mock LIM fluctuation map of the CO emission (with no noise added). Right: Lyα luminosity of each DM halo. The halos that would actually be detected by the mock survey and thus included in the galaxy catalogue are shown as larger cyan circles in all three panels.