Hydrogen Epoch of Reionization Array

Cosmic reionization corresponds to the epoch when the neutral intergalactic medium (IGM) is reionized by the first luminous objects (stars, black holes). Probing this last unexplored phase of cosmic evolution was emphasized by the astronomy community in the 2010 Decadal Survey the primary area with extraordinary ‘discovery potential’ in the study of cosmic structure formation:

 ‘A great mystery now confronts us: When and how did the first galaxies form out of cold clumps of hydrogen gas and start to shine—when was our “cosmic dawn”? Observations and calculations suggest that this phenomenon occurred when the universe was roughly half a billion years old, when light from the first stars was able to ionize the hydrogen gas in the universe from atoms into electrons and protons—known as the epoch of reionization.’

The HERA program aims to answer the primary questions: what objects first lit up the Universe and reionized the neutral IGM? Over what redshift range did this occur? How did the process proceed, leading to the large scale galaxy structure seen today.

In a phased build-out, HERA will construct 352 14-meter antennas in the Karoo Astronomy Reserve in the Northern Cape of South Africa.  Construction has started, with initial commissioning observations by the end of 2015 with 19 elements.