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Paper: Reionisation: the Role of Globular Clusters
Volume: 322, The Formation and Evolution of Massive Young Star Clusters
Page: 509
Authors: Ricotti, M.
Abstract: The sources of radiation able to reionise hydrogen in the intergalactic medium (IGM) by redshift z ~ 6 are still unknown. Observations at lower redshift seem to indicate that only a small fraction, <fesc>, of hydrogen ionising radiation emitted from massive stars can escape unabsorbed by the galaxy into the IGM. High redshift galaxies are expected to be more compact and gas rich than present day galaxies, consequently <fesc> from their disks or spheroids could be very small. But if the sites of star formation are off-centre and the star formation efficiency of proto-clusters is high, then the mean <fesc> calculated for these objects only, is expected to be close to unity. This mode of star formation is consistent with several models for globular clusters formation. Using simple arguments based on the observed number of globular cluster systems in the local universe and assuming that the oldest globular clusters formed before reionisation and had <fesc> ~ 1, I show that they produced enough ionising photons to reionise the IGM at z ≈ 6.
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