Inhomogeneous reionization of the intergalactic medium regulated by radiative and stellar feedbacks

We study the inhomogeneous reionization in a critical density CDM universe resulting from stellar sources, including Population III objects. The spatial distribution of the sources is obtained from high-resolution numerical N-body simulations. We calculate the source properties, taking into account a self-consistent treatment of both radiative (i.e. ionizing and H-2-photodissociating photons) and stellar (i.e. SN explosions) feedbacks regulated by massive stars. This allows us to describe the topology of the ionized and dissociated regions at various cosmic epochs, and to derive the evolution of H, He and H-2 filling factors, soft UV background, cosmic star formation rate and the final fate of ionizing objects. The main results are: (i) galaxies reionize the intergalactic medium by z approximate to 10 (with some uncertainty related to the gas clumping factor), whereas H-2 is completely dissociated already by z approximate to 25; (ii) reionization is mostly caused by the relatively massive objects which collapse via H line cooling, while objects the formation of which relies on H-2 cooling alone are insufficient for this purpose; (iii) the diffuse soft UV background is the major source of radiative feedback effects for z less than or equal to 15; at higher z direct flux from neighbouring objects dominates; (iv) the match of the calculated cosmic star formation history with that observed at lower redshifts suggests that the conversion efficiency of baryons into stars is approximate to 1 per cent; (v) we find that a very large population of dark objects which failed to form stars is present by z approximate to 8. We discuss and compare our results with similar previous studies.