LyC escape from sphinx galaxies in the Epoch of Reionization

We measure escape fractions, f(esc), of ionizing radiation from galaxies in the sphinx suite of cosmological radiation-hydrodynamical simulations of reionization, resolving haloes with M-vir greater than or similar to 7.5 x 10(7) M(circle dot)with a minimum cell width of approximate to 10 pc. Our new and largest 20 co-moving Mpc wide volume contains tens of thousands of star-forming galaxies with halo masses up to a few times 10(11) M-circle dot. The simulated galaxies agree well with observational constraints of the ultraviolet (UV) luminosity function in the Epoch of Reionization. The escape fraction fluctuates strongly in individual galaxies over time-scales of a few Myr, due to its regulation by supernova and radiation feedback, and at any given time a tiny fraction of star-forming galaxies emits a large fraction of the ionizing radiation escaping into the intergalactic medium. Statistically, f(esc) peaks in intermediate-mass, intermediate-brightness, and low-metallicity galaxies (M-* approximate to 10(7) M-circle dot, M-1500 approximate to -17, Z less than or similar to 5 x 10(-3) Z(circle dot)), dropping strongly for lower and higher masses, brighter and dimmer galaxies, and more metal-rich galaxies. The escape fraction correlates positively with both the short-term and long-term specific star formation rate. According to sphinx, galaxies too dim to be yet observed, with M-1500 greater than or similar to -17, provide about 55 per cent of the photons contributing to reionization. The global averaged f(esc) naturally decreases with decreasing redshift, as predicted by UV background models and low-redshift observations. This evolution is driven by decreasing specific star formation rates over cosmic time.

Automated summary

We measured and simulated the escape fractions of ionizing radiation from galaxies during reionization. The escape fraction fluctuates strongly within individual galaxies and correlates with galaxy mass, brightness, and metallicity. The escape fraction decreases over time and correlates positively with both short-term and long-term specific star formation rates.