An ionised bubble powered by a proto-cluster at z = 6.5
  We show herein that a proto-cluster of Ly$\alpha$ emitting galaxies,
spectroscopically confirmed at redshift 6.5, produces a remarkable number of
ionising continuum photons. We start from the Ly$\alpha$ 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.
