New Results from The Cosmic Dawn (CoDa) Project: Simulating Reionization and Galaxy Formation*

I summarize the latest progress in modelling reionization by large-scale simulations by The Cosmic Dawn (“CoDa”) Project.  When the first galaxies formed stars whose UV radiation escaped into the cold, neutral intergalactic medium, they created giant H II regions that grew in size and number until they overlapped.  Reionization and its back-reaction on the galaxies that caused it were fundamentally inhomogeneous in space and time.  This means galaxy formation and reionization were correlated and fully-coupled from the beginning, imprinting each other with observable consequences. Star formation suppression, for example, may explain the underabundance of Local Group dwarfs relative to CDM N-body predictions.  The CoDa Project recently achieved a new milestone – CoDa III -- the largest radiation-hydrodynamics simulation to date of fully-coupled reionization and galaxy formation, in a ~ 1 0 0  c M p c  volume,  large enough to model b o t h  global and local  reionization, with 8192^3 particles and cells, enough resolving power to follow all atomic-cooling galactic halos. CoDa III required running hybrid CPU-GPU code RAMSES-CUDATON on Oak Ridge supercomputer Summit for 10 days, on 131,072 processors and 24,576 GPUs.  Its results and observational predictions will be presented.