Abstract

In this talk, I will firstly present a spectroscopic case study of a 30× lensed galaxy at z=5. Detections of the C IV and [Ne III ] lines allow us to constrain the origin of the hard radiation field, the ionisation parameter, and the metallicity, while observed Mg II emission might prove a key tracer of escaping ionising radiation for JWST . Before JWST , however, we can already spectroscopically probe galaxies in the Epoch of Reionisation (EoR) with ALMA , whose recent detections of the far-infrared [CII] 158 μm and [OIII] 88 μm emission lines have opened a new observational window for studying galaxies at the highest redshift. In this talk, I will furthermore present new [OIII] 88 μm observations of four galaxies at z=7 recently detected by ALMA in [CII], allowing a multi-wavelength comparison combined with new deep HST images of the rest-frame UV. The [OIII] emission, corresponding to diffuse, highly ionised gas, and [CII] emission, tracing neutral gas and photon dissociation regions, allow some of the first explorations of the interstellar medium in the EoR.