Patrick Valageas web page

After recombination (redshift z~1200) the gas which fills the universe is made of neutral atoms (mainly hydrogen and helium). However, observations show that the gas seen along the lines of sight from the Earth up to distant quasars (z~6) is ionized. Therefore, the universe must have been reionized at some intermediate redshift. In usual scenarios this is due to the radiation emitted by the first stars. One of the tests which models of structure formation must satisfy is thus to be able to reionize the universe while matching obervations at low redshifts (galaxy luminosity function,..).

Articles:

• 2001, A&A, 367, 1
  Imprint of patchy reionization onto the CMB (kinetic SZ effect).
  
• 1999, A&A, 350, 725
  The evolution with redshift of the entropy of the IGM (due to the radiation from stars and quasars). Effect on the entropy of the intra-cluster gas.
  
• 1999, A&A, 347, 1
  The reheating and reionization history of the universe (by stars and quasars).