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Astron. Astrophys. 345, 380-390 (1999)

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Can the reionization epoch be detected as a global signature in the cosmic background?

P.A. Shaver 1, R.A. Windhorst 2, P. Madau 3 and A.G. de Bruyn 4,5

1 European Southern Observatory, Karl-Schwarzschild-Strasse 2, D-85748 Garching bei München, Germany
2 Arizona State University, Department of Physics and Astronomy, Tempe, AZ 85287-1504, USA
3 Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA
4 Netherlands Foundation for Research in Astronomy, Postbus 2, 7990 AA Dwingeloo, The Netherlands
5 Kapteyn Astronomical Institute, Postbus 800, 9700 AV Groningen, The Netherlands

Received 6 October 1998 / Accepted 5 February 1999


The reionization of the Universe is expected to have left a signal in the form of a sharp step in the spectrum of the sky. If reionization took place at [FORMULA], a feature should be present in the radio sky at [FORMULA] MHz due to redshifted H I 21-cm line emission, accompanied by another feature in the optical/near-IR at [FORMULA]m due to hydrogen recombination radiation. The expected amplitude is well above fundamental detection limits, and the sharpness of the feature may make it distinguishable from variations due to galactic and extragalactic foregrounds.

Because this is essentially a continuum measurement of a signal which occurs over the whole sky, relatively small telescopes may suffice for detection in the radio. In the optical/near-IR, a space telescope is needed with the lowest possible background conditions, since the experiment will be severely background-limited.

Key words: cosmology: early Universe – cosmology: diffuse radiation – cosmology: observations – cosmology: cosmic microwave background

Send offprint requests to: P.A. Shaver (pshaver@eso.org)

© European Southern Observatory (ESO) 1999

Online publication: April 19, 1999