2016 AAAS Annual Meeting (February 11-15, 2016)

February 10 - 15, 2016

Radio Astronomy on Three Continents: First Stars and the Epoch of Reionization

The first stars in the universe reversed the long cooling period of the first 0.7 billion years—the result of rapid expansion and decreasing density—when hydrogen and helium became neutral in the absence of ultraviolet light. In the midst of that expansion, locally dense regions collapsed into stars, and bright radiation from these stars heated and ionized the surrounding gas; this was the Epoch of Reionization. As more stars formed, the ionization spread, until it encompassed almost all baryonic mass. Today, the intergalactic medium is nearly fully ionized. Partially ionized hydrogen from the Epoch of Reionization has never been seen, as its most important spectral line at 1.4 GHz is redshifted to 150 MHz, in the middle of the TV band. The long wavelength of this redshifted light also makes cosmic objects blurry at the diffraction limit of normal telescopes. To overcome these problems, three new radio telescopes have been built in the last few years: the largest one, LOFAR, spans most of Northern Europe; and MWA and PAPER are in Australia and South Africa. These international projects are the beginnings of the Square Kilometer Array, which will probe the universe in radio waves at a sensitivity and resolution rivaling the optical images made by the Hubble Space Telescope. This symposium highlights the early results from these three new telescopes and the instruments used, with a view toward observing the Epoch of Reionization.