Feedback-regulated star formation and escape of LyC photons from mini-haloes during reionization

Reionisation in the early Universe is likely driven by dwarf galaxies. Using cosmological RHD simulations, we study star formation and the escape of Lyman continuum (LyC) photons from mini-haloes with Mhalo<108Msun. We find that feedback reduces star formation very efficiently in mini-haloes, resulting in the stellar mass consistent with the empirical stellar mass-to-halo mass relation derived in the local Universe. Because star formation is stochastic and dominated by a few gas clumps, the escape fraction in mini-haloes is generally determined by photo-ionization, rather than supernova explosions. We find that the photon number-weighted mean escape fraction in mini-haloes is higher (20-40%) than that in atomic-cooling haloes. Despite their high escape fractions, LyC photons from mini-haloes are of minor importance for reionization due to inefficient star formation. We confirm previous claims that stars in atomic-cooling haloes with masses $10^8M_{sun}$$10^{11}M_{sun}$ are likely to be the most important source of reionization.