The first billion years of the Universe is a key period for the evolution of the intergalactic medium and the formation of galaxies. As the first stars form, their UV photons propagate, carving ionised regions which ultimately percolate, marking the end of the epoch of reionization, However, in this simple picture many questions remain. Which galaxies are the main sources of ionising radiation? The massive ones, or their more numerous, low mass, counterparts? What is the contribution of AGNs? How does the rise of the UV background affect galaxy formation?
Recently, important progress has been made in the observation of this epoch, leading, for instance, to the build-up of significant samples of galaxies at z between 6 and 10, thanks to space and ground facilities. Their multi-wavelength study is starting to yield useful constraints on their stellar populations, as well as chemical and dynamical properties of their gas. In the meantime, the spectra of high redshift quasars are used in a continued effort to probe the properties of the intergalactic medium at high z. However, despite this progress, the above questions are far from settled, and the community is eagerly waiting a new generation of instruments, such as JWST, to provide new constraints.
Radio facilities in construction, such as SKA, or already in operation, have the common goal of directly detecting the 21cm signal from the reionizing Universe. While this is extremely challenging, in particular due to radio foregrounds, this approach is bound to revolutionise our understanding of the epoch of reionisation. Only the combined study of the high redshift galaxy population and the intergalactic medium will reveal the full story of early galaxy formation.
On the theoretical front, a new breed of numerical simulations of galaxy formation now allows to account for richer physics, in particular ionising radiation, while reaching unprecedented mass resolution and volumes. These advances are extremely helpful for studying and interpreting the build-up of the first generation of galaxies and quasars, and for understanding their role in reionizing the universe.
The goal of this meeting is to bring together a wide community of observers and theorists to discuss recent progress and challenges, as well as future perspectives for reionization and high-redshift studies. Among the key topics to be explored at this meeting include:
The June R&S2018 meeting will be hosted by the Observatoire astronomique de Strasbourg, in Strasbourg, France. The meeting will take place at the nouveau Patio, located on the campus of the University of Strasbourg not far from the observatory.