Simba-EoR: Early galaxy formation in the Simba simulation including a new sub-grid interstellar medium model

We update the dust model present within the Simba galaxy simulations with a self-consistent framework for the co-evolution of dust and molecular hydrogen populations in the interstellar medium, and use this to explore z ≥ 6 galaxy evolution. In addition to tracking the evolution of dust and molecular hydrogen abundances, our model fully integrates these species into the Simba simulation, explicitly modelling their impact on physical processes such as star formation and cooling through the inclusion of a novel two-phase sub-grid model for interstellar gas. In running two high-resolution simulations down to z ~ 6 we find that our Simba-EoR model displays a generally tighter concordance with observational data than fiducial Simba. Additionally we observe that our Simba-EoR models increase star formation activity at early epochs, producing larger dust-to-gas ratios consequently. Finally, we discover a significant population of hot dust at ~ 100 K, aligning with contemporaneous observations of high-redshift dusty galaxies, alongside the large ~ 20 K population typically identified.