  We implemented Population III (Pop. III) star formation in mini-halos within
the MERAXES semi-analytic galaxy formation and reionisation model, run on top
of a N-body simulation with $L = 10 h^{-1}$ cMpc with 2048$^3$ particles
resolving all dark matter halos down to the mini-halos ($\sim 10^5 M_\odot$).
Our modelling includes the chemical evolution of the IGM, with metals released
through supernova-driven bubbles that expand according to the Sedov-Taylor
model. We found that SN-driven metal bubbles are generally small, with radii
typically of 150 ckpc at z = 6. Hence, the majority of the first galaxies are
likely enriched by their own star formation. However, as reionization
progresses, the feedback effects from the UV background become more pronounced,
leading to a halt in star formation in low-mass galaxies, after which external
chemical enrichment becomes more relevant. We explore the sensitivity of the
star formation rate density and stellar mass functions on the unknown values of
free parameters. We also discuss the observability of Pop. III dominated
systems with JWST, finding that the inclusion of Pop. III galaxies can have a
significant effect on the total UV luminosity function at z = 12 - 16. Our
results support the idea that the excess of bright galaxies detected with JWST
might be explained by the presence of bright top-heavy Pop. III dominated
galaxies without requiring an increased star formation efficiency.
