Cosmology --- The Thermal History of the Universe ---

The fist paper on the cosmic reionization was written by Y. Sofue in 1968 as his Master Thesis on the formation of galaxies by thermal instability. The work was published in 1969.

It was shown that the intergalactic matter was reionised and heated up to 10 million K at redshift of z=3000, or at cosmic time t=0.1 million year soon after the recombination in the expanding Universe since the Big Bang.