Observational Constraints on Self-consistent Reionization Models
T. Roy Choudhury, A. Ferrara
SISSA/ISAS, via Beirut 2-4, 34014 Trieste, Italy

A self-consistent formalism to jointly study cosmic reionization and the thermal history of the IGM is presented. The model implements most of the relevant physics governing these processes, such as the inhomogeneous IGM density distribution, three different sources of ionizing photons (PopIII stars, PopII stars and QSOs), and radiative feedback. By constraining the free parameters with available data on redshift evolution of Lyman-limit systems, Gunn-Peterson and electron scattering optical depths, Near InfraRed Background (NIRB), and cosmic star formation history, we select a fiducial model, whose main predictions are: (i) H was completely reionized at z » 15, while HeII must have been reionized by z » 12. At z » 8, HeIII suffered an almost complete recombination as a result of the extinction of PopIII stars. (ii) A QSO-induced complete HeII reionization occurs at z=3.5; a similar double H reionization does not take place due to the large number of photons above 1 Ryd from Pop II stars. Such a model not only relieves the tension between the Gunn-Peterson optical depth and WMAP observations, but also accounts self-consistently for all known observational constraints. We discuss two likely applications of the model, namely, (i) to understand the ionization state of the universe at high redshifts from high redshift quasar absorption spectra, and (ii) to verify the astrophysical constraints on extended reionization models.

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