Abstract

The Epoch of Reiniosation describes the cosmic period in which the Universe went from being dark and neutral, to being transparent to radiation. Understanding the first galaxies responsible for lighting up the Universe is of utmost importance for unveiling the mysteries of this epoch.

In this talk I will present work done through the use of deep NIR Cam imaging from the JWST Advanced Deep Extragalactic Survey (JADES) to study the evolution of the ionising photon production efficiency, ξion, with redshift (3 < z < 9). When observing Lyman-alpha emitters (LAEs) and emission-line galaxies (ELGs), we find that low-mass galaxies with bursty star formation histories are more efficient in producing ionising radiation, and could represent the main drivers of reionisation. However, we find that the observed increase of ξion with redshift depends on the nature of the sample: the trends observed in LAEs and ELGs are less significant when a stellar-mass complete sample is used instead.

By combining these results we find that galaxies are likely the main drivers of reionisation, and that there is no crisis in the cosmic ionising budget when a stellar-mass complete sample is considered.