The Epoch of Reionization

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This figure shows a sketch of the likely development of the Epoch of Reionization. About 500,000 years after the Big Bang (z ≈1000) hydrogen recombined and remained neutral for a few hundred million years during the dark ages. At a redshift, z ≈15, the first stars, galaxies and quasars began to form, heating and reionizing the hydrogen gas. The neutral IGM can be observed with LOFAR up to z ≈11.5 through its redshifted 21cm spin-flip transition. However, many atmospheric, galactic and extra-galactic emission contaminate the 21 cm signal.

Saleem Zaroubi (Kapteyn Astronomical Institute, Univ. of Groningen)
The Universe’s dark ages end with the formation of the first generation of galaxies. These objects start emitting ultraviolet radiation that carves out ionized regions around them. After a sufficient number of ionizing sources have formed, the ionized fraction of the gas in the Universe rapidly increases until hydrogen becomes fully ionized. This period, during which the cosmic gas went from neutral to ionized, is known as the Universe’s Epoch of Reionization . The Epoch of Reionization is related to many fundamental questions in cosmology, such as properties of the first galaxies, physics of (mini-)quasars, formation of very metal-poor stars and a slew of other important research topics in astrophysics. Hence uncovering it will have far reaching implications on the study of structure formation in the early Universe. This chapter reviews the current observational evidence for the occurrence of this epoch, its key theoretical aspects and main characteristics, and finally the various observational probes that promise to uncover it. A special emphasis is put on the redshifted 21 cm probe, the various experiments that are currently being either built or designed, and what we can learn from them about the Epoch of Reionization…..
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Written by physicsgg

June 4, 2012 at 9:17 am


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