Exploring the Epoch of Reionisation through its evolving topology

Emilie Thelie (Université de Strasbourg) - hybrid seminar (in-person in Salle NEF + remote via Zoom)

Abstract:
During the Epoch of Reionisation (EoR), the large scale structures of the Universe emerge while ionising the intergalactic gas. It creates bubbles of ionised gas around the first galaxies. These bubbles percolate near the end of the EoR, at a redshift of approximately 6. I will present an approach that allows me to study the evolution of the EoR within reionisation time (or redshift) treion(r) (zreion(r)) maps from models of numerical simulations (Thélie et al. 2022, Thélie et al. accepted in A&A, arXiv:2209.11608). I use EMMA cosmological simulations (Aubert+15) and 21cmFAST semi-analytical ones (Mesinger+11) of the EoR with a 1 Mpc/h resolution. Thanks to topological measurements on treion(r), I can extract information about the evolving process of reionisation: reionisation history with its filling factor, ionisation front velocity with its gradients, ionised/neutral bubbles size evolution with its isocontours length, reionisation seeds count with the critical points probability distribution function, and fronts percolation with the skeleton length. In Thélie et al. 2022, I studied the spatial configuration of reionisation patches and show that reionisation fronts predominantly propagate along the density filaments in our simulations. In Thélie et al. accepted in A&A, arXiv:2209.11608, the reionisation time field is proven to be rather close to a gaussian random field when its resolution is closed to that of the upcoming 21 cm images of the SKA radio-telescope. I will present a summary of these results and discuss future applications for this new framework to study reionisation.