Obscured fraction f_obsc​ = ​1 − e^−τ as a function of redshift z along the threshold line for FFB, according to Eq. (49). The corresponding extinction A_UV is shown on the right y-axis. The toy models of the shell (blue) and disk (orange) are shown, with similar results. The color bands show the uncertainty corresponding to ϵ_max = 0.2 − 1 about ϵ_max​ = ​0.5. We see a significant decline in obscuration with redshift. The solid lines are for Z_in​ = ​0.1, typical in the FFB regime. Shown for comparison (dashed line) are the results for Z_in​ = ​1, valid at later times, where the obscuration is stronger. Shown for reference are tentative observations (Curti et al. 2023; Jones et al. 2023; Hu et al. 2024; assuming a Calzetti et al. 2000 attenuation law), which lie between the FFB predictions for shells and disks.