Constraining cosmic reionization with quasar, gamma ray burst, and Lya emitter observations

Understand

We investigate the cosmic reionization history by comparing semi-analytical models of the Lya forest with observations of high-z quasars and gamma ray bursts absorption spectra.

• In order to constrain the reionization epoch z_rei, we consider two physically motivated scenarios in which reionization ends either early (ERM, z_rei>= 7) or late (LRM, z_rei~6).
• We analyze the transmitted flux in a sample of 17 quasars spectra at 5.7<z<6.4 and in the spectrum of the gamma ray burst 050904 at z=6.3, studying the wide dark portions (gaps) in the observed absorption spectra.
• By comparing the statistics of these spectral features with our models, we conclude that current observational data do not require any sudden change in the ionization state of the IGM at z~6, favouring indeed a highly ionized Universe at these epochs, as predicted by the ERM.