Probing the end of the reionization epoch with the most distant galaxies


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

The last few 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, namely Ly alpha emitters and Lyman
break galaxies. In particular I will review the current constrains
that we can place on the reionization epoch using the first
statistical samples of spectroscopically confirmed z=7 Lyman break
galaxies, the evolution of the luminosity functions and of the
clustering strength of Ly alpha emitters.

Finally, I will present very recent ALMA observations which reveal,
for the first time the nature and physical properties of these
primeval galaxies that were probably responsible for the reionization.