Joint Astrophysical Colloquium
Reionization and the first billion years of galaxy formation with the SPHINX simulations
Joakim Rosdahl (CNRS - Centre de Recherche Astrophysique de Lyon)
Thursday 04/04/2024 @ 11:30, Sala Antonio Sollima (IV piano Battiferro)
The Epoch of Reionization marks a shift from a cold neutral Universe to a warm ionised one, a transition that ended billion years after the Big Bang and was likely powered by radiation emitted from young massive stars in the first galaxies. This epoch is a frontier research field in astronomy and the main focus of the JWST and the upcoming SKA. Observations still provide a limited picture of the first galaxies and reionization. Comprehensive cosmological simulations performed with gravitational-radiation-hydrodynamics are necessary to improve our understanding. The SPHINX suite of simulations (https://sphinx.univ-lyon1.fr) take advantage of new method developments and extensive access to supercomputers to model reionization, using a complex and unprecedented mix of physics and sub-grid models in cosmological volumes. For the first time we can resolve the emission of stellar radiation through and out of the inter-stellar medium of tens of thousands of star-forming galaxies, all forming and evolving together in the same simulation, hence capturing the interplay of intra- and inter-galactic scales in the reionization process. I will describe the simulations and show results from our flagship 20 cMpc wide SPHINX20 volume. Among those results, I will address which galaxies -- and under which conditions -- experience high ionizing escape fractions and dominate the photon budget in the reionization process. I will discuss the redshift-evolution of the escape fraction and the processes determining its evolution, describe how we can infer from SPHINX what are the best observational diagnostics for high escape fractions in real galaxies, and present the recent public data release of mock-observations of SPHINX galaxies.