The combination of the z=0-13. 5 cosmic star formation history and active galactic nuclei (AGN) luminosity history as inferred by the James Webb Space Telescope is connected to the cosmic spectral energy distribution (CSED) to explore the sources of reionisation. We compute the redshift evolution of the corresponding cosmic ionising photon emissivity, the neutral fraction and the cosmic microwave background optical depth. We use the generative SED modelling code ProSpect to bracket the ionising emissivity between escape fractions of f₄ₒ₂ = 1 - 100\% for both the stars and AGN. Stars alone could have achieved reionisation by z 6 with f₄ₒ₂ 10-30\%, depending on the metallicity. On the other hand, AGN by themselves would have struggled to produce sufficiently many ionising photons even with f₄ₒ₂ = 100\%. A hybrid model containing both stars and AGN is explored where we find best fit (median 1σ) f₄ₒ₂= 12\% (12^+10-₁₁\%) for the stars and f₄ₒ₂= 63\% (79^+21-₄₄\%) for the AGN, maintained at all redshifts. In essence, the joint growth of stellar mass and super massive black holes produces neither more or less ionising photons than needed to reionise 99\% of the intergalactic medium by z 6.
D’Silva et al. (Mon,) studied this question.