First results from the THESAN radiation-hydrodynamic simulations of the Epoch of Reionization

I will present results from the THESAN project, a suite of large volume (~100 cMpc)³ cosmological radiation-hydrodynamic simulations that simultaneously model the large-scale statistical properties of the intergalactic medium (IGM) during reionization and the resolved characteristics of the galaxies responsible for it. THESAN offers a unique framework for high-redshift science by combining state-of-the-art galaxy formation (IllustrisTNG) and dust models with the Arepo-RT solver, with sufficient resolution to enable predictions down to the atomic cooling limit. The simulations have realistic ”late’ reionization histories and galaxy properties that match available constraints, e.g. halo mass and luminosity relations. I will discuss applications from the first set of papers, including bubble size distributions that imprint unique signatures for 21 cm cosmology and multi-tracer line intensity mapping, rapid evolution of the mean free path of ionizing photons, and emergence of the Lyman-alpha forest. I will discuss the utility of Lyman-alpha emitting galaxies (LAEs) and red damping-wing transmission as probes of reionization, which reveal nontrivial trends across different galaxies, sightlines, and frequency bands that can be modeled in the framework of covering fractions. Overall, THESAN produces a realistic IGM and galaxy population, providing a robust framework for future analysis of the high-redshift Universe.