Abstract Details
| Name: Vikram Khaire Affiliation: NCRA Conference ID: ASI2017_1352 Title : Helium Reionization and Spectral Energy Distribution of Quasars Authors and Co-Authors : NCRA Abstract Type : Oral Abstract Category : Extragalactic astronomy Abstract : We use recently measured He II optical depths to study their implications on the models of helium reionization and He II ionizing radiation background. The radiation with energy > 4 Ryd emitted from quasars ionize He II. The Intensity of this radiation depends on the quasar emissivity and their average spectral energy distribution (SED). Quasar emissivity is obtained through quasar luminosity functions. The average SED of quasars is usually obtained by fitting simple power laws to stacked spectrum of quasars at energy >1 Ryd. Till now, there are no observational detections of the quasar SED at energies > 4Ryd. However, it can be constrained using our cosmological radiative transfer code along with the recent measurements of He II optical depths. We find that for quasar luminosity function obtained in optical surveys, quasar SED prefers power-law index to be -1.8. We find similar conclusions for models that include faint x-ray emitting quasars which have been shown to reionize hydrogen without any contribution from galaxies. Its implications on the spectrum of ionizing background radiation will be discussed. |