Mapping the ionizing sources with CMB polarization measurements

With the three-year data, the Wilkinson Microwave Anisotropy Probe(WMAP3) produced a more accurate determination of the electron scattering optical depth, downwarding its value from τes = 0.17 ± 0.08 obtained with the first-year data (WMAP1) to τes = 0.09 ± 0.03. As a consequence, the structure formation in the ΛCDM best fit model obtained WMAP3 is delayed relative to that of WMAP1. We show that the delay of structure formation can not fully account for the reduction of τes from WMAP1 to WMAP3 when the radiative transfer effects and feedback mechanisms are took into account in computing the reionization history of the Universe. We also show that a PopIII stellar cluster with a mass of 80M⊙ and a heavy Larson initial mass function has an ionizing efficiency high enough to account fo r WMAP3 results, while in the case