PAPER: Precision Array to Probe the Epoch of Reionization

Don Backer (UCB Astronomy)

We are developing PAPER to detect neutral hydrogen structures in the early universe -- in the epoch of reionization when the first stars are forming and exciting the 21cm (1420-MHz) hydrogen line above the temperature of the ambient radiation field. Simulations by several groups suggest that the spin temperature excess will be ~10 mK on several arcmin scales in the redshift range 7 to 10 or higher (i.e., below 200 MHz). The polarized, galactic synchrotron and Faraday-rotating thermal gas foregrounds make this measurement very challenging. A square kilometer of collecting area is required to map individual structures. Our group is developing ~200 m^2 PAPER to take a small step toward this goal. PAPER is an array of broadband dipoles fixed on the ground whose responses are cross-correlated to allow imaging of the hemisphere of the sky drifting overhead. The correlator development is led by Astronomy student Aaron Parsons with support from CASPER, an SSL/RAL/BWRC electronics development group. The dipoles and electronics have been developed by Rich Bradley and his student Chataili Parashare (NRAO/UVA). Initial deployment will be at NRAO site in WV. This will be followed by deployment in the outback of Western Australia.