An ionised bubble powered by a proto-cluster at z = 6.5

Each dot is a galaxy that ionises its surroundings forming a bubble. These bubbles can grow depending of the galaxy ionising power and the bubbles can merge forming a larger bubble. With time all the bubbles will merge till the Universe become re-ionised.
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We show herein that a proto-cluster of Lyα emitting galaxies, spectroscopically confirmed at redshift 6.5, produces a remarkable number of ionising continuum photons. We start from the Lyα fluxes measured in the spectra of the sources detected spectroscopically. From these fluxes we derive the ionising emissivity of continuum photons of the proto-cluster, which we compare with the ionising emissivity required to reionise the proto-cluster volume. We find that the sources in the proto-cluster are capable of ionising a large bubble, indeed larger than the volume occupied by the proto-cluster. For various calculations we have used the model AMIGA, in particular to derive the emissivity of the Lyman continuum photons required to maintain the observed volume ionised. Besides, we have assumed the ionising photons escape fraction given by AMIGA at this redshift.