Abstract
According to the pancake theory of formation of large-scale structure in the Universe, gaseous pancakes are expected to form in the range of redshifts 5–10. One of the ways in which they should manifest their presence is through emission in the 21-cm line by their neutral hydrogen component. An aperture synthesis radio telescope has been used at 151 MHz to map the sky north of declination 82°. Data sampling was arranged to permit a differential mapping technique to be used, which enabled the continuum emission in the field to be almost entirely cancelled, to leave a residual rms level of 5 mJy. At the 2σ level, no sources were found in a 1 per cent redshift range around z = 8.4, the nominal survey redshift. The observations are found to provide new limits on the pancake population under certain Friedmann cosmologies.
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