The brighter galaxies reionised the Universe

Understand

Hydrogen in the Universe was (re)ionised between redshifts $z \approx 10$ and $z \approx 6$.

• The nature of the sources of the ionising radiation is hotly debated, with faint galaxies below current detection limits regarded as prime candidates.
• Here we consider a scenario in which ionising photons escape through channels punctured in the interstellar medium by outflows powered by starbursts.
• We take account of the observation that strong outflows occur only when the star formation density is sufficiently high, and estimate the galaxy-averaged escape fraction as a function of redshift and luminosity from the resolved star formation surface densities in the EAGLE cosmological hydrodynamical simulation.