Shedding light on the Epoch of Reionization

Reionization represents an important epoch in the history in the 
Universe, when the first stars and galaxies gradually ionize the neutral 
hydrogen in the intergalactic medium (IGM). Understanding the nature of
the ionizing sources, the associated ionization of the IGM, and its
impact on subsequent structure formation and galaxy evolution by means
of radiative feedback effects, represent key outstanding questions in
current astrophysics.
In the past few years high-redshift galaxy observations and simulations
have significantly extended our knowledge on the nature of high-redshift
galaxies. However, essential properties such as the escape fraction of
ionizing photons from galaxies into the intergalactic medium and their
dependency on galactic properties remain essentially unknown, but
determine significantly the distribution and time evolution of the
ionized regions during reionization. Analysing this ionization topology
by means of the neutral hydrogen sensitive 21cm signal with radio
interferometers such as SKA offers a complementary and unique
opportunity to determine the nature of these first galaxies. A
particular promising avenue in constraining the reionization history and
topology lies in cross-correlating these 21cm signal maps with the
location of high-redshift galaxies. Among high-redshit galaxies,
Lyman-alpha emitters (LAEs) represent a unique sample with their
visibility being strongly dependent on the ionization state of the
intergalactic medium.
In this talk, I will show how the 21cm signal and LAEs trace
reionization, how the 21cm signal can allow us to infer galactic
properties such as the escape fraction of ionizing photons, and what
synergising future measurements of the 21cm signal and LAEs with SKA and
Subaru Hyper Suprime-Cam or WFIRST can reveal about the reionization
history and topology.