Towards simulating the Epoch of Reionization on exascale
supercomputers

Speaker : Pierre Ocvirk

Abstract :

The Epoch of Reionization (EoR) represents a fundamental phase
transition in cosmic history, demanding sophisticated numerical simulations
to interpret observations of the high-z Lyman alpha forest, combined with
HST/JWST, and upcoming 21cm surveys. Our latest Cosmic Dawn III
simulation has redefined the state-of-the-art by simultaneously and
precisely predicting multiple EoR observables: the evolution of the neutral
Hydrogen fraction, Thomson scattering optical depth, ionizing photon rates,
Lyman-α forest optical depth distributions, and ionizing mean free path
evolution. However, critical limitations persist, including insufficient spatial
resolution for internal galaxy physics and box sizes still to small for
interpreting observed volumes like ASPIRE/EIGER. Breaking through these
barriers requires exascale computing and new computational frameworks,
which I will illustrâtes. Additionally, I will discuss the underexplored
limitations of the M1 radiative transfer model, presenting new work by PhD
student Mei Palanque on Pn methods coupled to photochemistry, which
quantifies M1 artifacts and opens pathways to more accurate EoR
modeling.