Parallel sessions

Understanding first light - the formation of the first stars and galaxies in the early Universe - remains a fundamental and challenging frontier in observational cosmology. Such objects form in a largely neutral medium and cause the most dramatic phase change of the Universe re-ionisation. While remarkable progress in both observations and theory has been made, our understanding of galaxies and their impact on the high-z intergalactic medium in the first billion years since the big bang is still restricted to only the brightest probes probing a handful of sight-lines to z>7. A number of fundamental questions remain unresolved, including: the nature of the faint high-z galaxy population, the production and escape of ionising photons from galaxies in the reionisation era, the role of nascent black holes at high-z, the evolution and influence of dust, the energetics and duration of reionisation, the development of structure and detecting the first stars. Owing to the increased sensitivity of forthcoming ground- and space-based multi-wavelength telescopes, this decade will see significant advances leading to strong constraints on galaxy evolution and formation models. Building on Hubble's legacy, Webb - whose first scientific observations are expected at the time of the meeting - will revolutionise our ability to probe further down the luminosity function and reveal both the chemical compositions as well as formation histories of galaxies in the reionisation era, complemented by large bright samples from wide-area surveys with Euclid, Rubin and Roman. The ELTs and ALMA will deliver exquisitely detailed information on the gaseous and dusty media of such galaxies, coupled to constraints on the role and influence of early black holes from Athena and radio observations. The plethora of sensitive radio facilities including the SKA & pathfinders are poised to uniquely map the influence of the first galaxies on the large-scale IGM in 3D. By bringing together observers and theorists, this session will capitalise on and prepare for these exciting developments. We will focus on three key themes at z>7: - observations, theory & simulations of the IGM - physical properties of galaxies and AGN analogous to/in the reionisation era - theory/simulations of galaxies and AGN