Shedding light on the Epoch of Reionization with the 21cm signal  [slides]

Abstract

The Epoch of 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 the Square Kilometre Array (SKA) offers a complementary and unique opportunity to determine the nature of these first galaxies and pin down the reionization history.

In this talk, I will discuss how synergising high-redshift galaxy observations with 21cm signal detections can provide constraints on reionization. Furthermore, I will show results from a self-consistent semi-numerical model of galaxy evolution and reionization, and discuss the potential of inferring galactic properties, as the escape fraction of ionizing photons, with the 21cm signal by means of its bispectrum.