Evolution of the ionising photon rate density as a function of redshift. In both panels, for reference, the solid lines represent the intrinsic ionising photon density for the different models studied, as marked. Shaded regions highlight the spread from the minimum to maximum values among the five runs with different random seeds. The two panels show the ‘escaping’ emissivity for the two f_esc models studied in this work for all galaxies (dashed lines) and those with M_* > 10⁹ M_⊙ (dotted lines). The left panel shows results for a constant value of f_esc needed to match reionisation constraints; the right panel shows results using f_esc values from Chisholm et al. (2022) as shown in Eq. (9). In both panels, points show observational constraints (from Becker & Bolton 2013; Bouwens et al. 2015; Becker et al. 2021; Rinaldi et al. 2024).