Abstract

The epoch of re-ionization is a fascinating time in the history of the Universe and many uncertainties still plague our understanding of when and how it occurred.

Lyman alphas emitting galaxies at high redshift offer a powerful probe to study both reionization and the process of galaxy formation. In particular Lyman alphas emission is an efficient tool for identifying young galaxies and for measuring how much neutral hydrogen is present in their environment, thus providing a reionization test that is independent of the Gunn-Peterson trough observations in quasar spectra.

The last two years have seen a number of discoveries that offered the first glimpse of the Universe at z=7, using both space and ground-based telescopes. I will review the most recent observational results on high redshift galaxies and the current constraints that we can place on the reionization epoch using the first statistical samples of spectroscopy confirmed z=7 Lyman break galaxies, the evolution of the luminosity functions and of the clustering strength of Lyalpha emitters.