Abstract

Cosmic reionization corresponds to the epoch when light from the first stars and black holes reionized the neutral Inter-Galactic Medium (IGM) that pervade the Universe following recombination. This period of ‘first new light’, about 1 Gyr after the Big Bang, remains the last epoch of cosmic structure formation to be tested and explored. I will summarize the latest constraints on cosmic reionization, principally based on the affect of Ly-alpha resonant scattering by the neutral gas. I will then focus on the potential to observe the evolution of the neutral IGM directly through the HI 21cm line. This new window on early large scale structure evolution has the potential to provide the ‘richest of cosmological data sets’, and is a primary science driver for the Square Kilometer Array. I will present details of the Precision Array to Probe the Epoch of Reionization, a low frequency SKA -pathfinder experiment in South Africa. PAPER has produced unprecedented wide field, low frequency images of the southern sky, and we have set the best (statistical) limits on the HI 21cm signal from reionization to date. I will conclude by presenting plans for the Hydrogen Epoch of Reionization Array, a 568 element array in South Africa that will provide a detailed characterization of the HI 21cm power spectrum and its evolution, as well as the potential for direct imaging of the largest scale structures during reionization.