Speaker
Description
Despite it being a fundamental milestone in our Universe’s evolution, the epoch of reionization (EoR) remains poorly understood. Luckily, recent years have witnessed a large increase both in observational datasets probing the EoR as well as sophisticated theoretical frameworks used to interpret this data. We introduce two novel, forward-modeling, implicit-likelihood inference frameworks designed to infer both the timing and the topology of the EoR. We demonstrate how recent high-redshift QSO spectra from XQR30+, combined with observed UV luminosity functions, already constrain the bulk of the EoR history to within \Delta z ~ 0.1, in a way that is robust to the choice of astrophysical model and without the inclusion of ad-hoc, “tunable" parameters. The topology of the EoR however remains a mystery. This topology tells us which sources reionized the Universe, and allows us to connect the growth of cosmic HII regions to the galaxies they contain. We showcase a novel framework to infer the local HII region surrounding groups of galaxies. We forward model the Lyman alpha spectra of galaxies as would be observed by NIRSpec on JWST, sampling all relevant sources of uncertainty, and taking into account each galaxy’s relative location in the local EoR topology. We find that observed galaxy number densities of ~0.003 cMpc^-3 are sufficient to estimate the size and position of the local HII region at percent level accuracy. Such number densities are well within the reach of future JWST surveys.
