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The Precision Array to Probe the Epoch of Reionization

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Cosmic reionization is the ‘final frontier’ in studies of cosmic structure formation, corresponding to the epoch when light from the first stars and black holes act to reionize the neutral intergalactic medium, a few hundred million years after the Big Bang. I will present a brief review of the concept of reionization, and exciting recent results that set the first constraints on the epoch of reionization. The latest studies of spectra of the most distant quasars suggest a substantially neutral IGM (> 10%) at z ~ 7. While revolutionary, current measures of cosmic reionization have fundamental limitations (namely, saturation at low neutral fraction). The most direct probe of the neutral IGM during reionization is through the 21cm emission line of hydrogen. I will present the design and recent results from the Precision Array to Probe the Epoch of Reionization. PAPER comprises two low frequency dipole arrays (120 to 180 MHz) to study the HI 21cm signal from the neutral IGM during reionization: a 32 element engineering test array in Green Bank WV, USA , and a 128 element science array in the Karoo, South Africa. Our design philosophy is to maintain well controlled and simple engineering specifications to mitigate the substantial systematic problems that these measurements entail (strong continuum foregrounds, very wide fields, large fractional bandwidths, and strong terrestrial interference). I will present the first all-sky images from our working arrays in the Karoo and Green Bank, details on the processing involved, and plans for expansion to the full science array. If time allows, I will close with a few words on the prospects of intensity mapping of the CO emission from the first galaxies, to obtain the ‘inverse view’ (relative to the HI 21cm studies) of the Cosmos during reionization

This talk is part of the Cavendish Astrophysics Seminars series.

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