MERAXES is a semi-analytic model of galaxy formation and reionization designed for studying galaxy formation and growth during reionization.

MERAXES is described in Mutch et al. 2016 and has undergone several updates including: AGN feedback (Qin et al. 2017), a more refined method for the supernova feedback ( Qiu et al. 2019) and mini-halo physics including Pop. III star formation and chemical enrichment of the IGM ( Ventura et al. 2024).

Its key features include the horizontal processing of merger trees constructed from an N-body simulation and the incorporation of the semi-numerical reionization algorithm, 21cmFAST, that allows a temporally and spatially coupled treatment of reionization. For each galaxy in MERAXES the following physical processes are tracked: gas accretion and cooling, star formation, supernova feedback (gas ejection and metal enrichment) and mergers. The reionization process is followed self-consistently with galaxy formation and evolution, computing the time and spatial evolution of the ionized bubbles within the intergalactic medium (IGM), and its feedback on the gas content in galaxies. Together with reionization, also the thermal state and the metallicity evolution of the IGM is followed.

Meraxes has been used in more than 20 refereed papers .

The source code for the latest version including the instructions for compilation and execution are available here .