SPACE.com -- Some of the Universe's First Galaxies Discovered
"Ouchi and his team compared their observations with those from other
studies looked at the rates of star formation, which can be gleaned from
data on the density and brightness of galaxies, and found that they were
dramatically lower from 800 millions years to about one billion years
after the Big Bang, than thereafter.

Accordingly, they calculated that the rate of ionization would be very
slow during this early time, because of this low star-formation rate.

"We were really surprised that the rate of ionization seems so low,
which would constitute a contradiction with the claim of NASA's WMAP
satellite. It concluded that reionization started no later than 600
million years after the Big Bang," Ouchi said. "
http://www.space.com/scienceastronomy/091106-earliest-galaxies-univer...