%0 Generic %1 mitra2016cosmic %A Mitra, Sourav %A Choudhury, T. Roy %A Ferrara, Andrea %D 2016 %K agn contribution ionisation %T Cosmic reionization after Planck II: contribution from quasars %U http://arxiv.org/abs/1606.02719 %X In the light of the recent Planck downward revision of the electron scattering optical depth, and of the discovery of a faint QSO population at $z > 4$, we reassess the actual contribution of quasar to cosmic reionization. To this aim, we extend the data-constrained semi-analytic reionization model, based on a rigorous MCMC analysis developed in our previous works, and study the implications of such high-$z$ QSOs on the reionization history. We find that, the quasars can alone reionize the Universe only for models with very high AGN emissivities at high redshift. However, these models predict a too rapid evolution of Lyman limit systems with respect to the observed one. Models with relatively lower emissivities at high-$z$, but consistent with the present datasets, still require a non-zero escape fraction of $\sim12\%$ from early-epoch galaxies. For such models, reionization happens over a shorter period of time; mean neutral hydrogen fraction becomes $\sim10^-4$ at $z=5.8$ from $\sim0.8$ at $z=9.0$. Future observations of faint quasars in the early universe will be necessary to put tighter constraints on the quasar-dominated reionization scenario.

@misc{mitra2016cosmic, abstract = {In the light of the recent Planck downward revision of the electron scattering optical depth, and of the discovery of a faint QSO population at $z > 4$, we reassess the actual contribution of quasar to cosmic reionization. To this aim, we extend the data-constrained semi-analytic reionization model, based on a rigorous MCMC analysis developed in our previous works, and study the implications of such high-$z$ QSOs on the reionization history. We find that, the quasars can alone reionize the Universe only for models with very high AGN emissivities at high redshift. However, these models predict a too rapid evolution of Lyman limit systems with respect to the observed one. Models with relatively lower emissivities at high-$z$, but consistent with the present datasets, still require a non-zero escape fraction of $\sim12\%$ from early-epoch galaxies. For such models, reionization happens over a shorter period of time; mean neutral hydrogen fraction becomes $\sim10^{-4}$ at $z=5.8$ from $\sim0.8$ at $z=9.0$. Future observations of faint quasars in the early universe will be necessary to put tighter constraints on the quasar-dominated reionization scenario.}, added-at = {2016-06-10T09:43:04.000+0200}, author = {Mitra, Sourav and Choudhury, T. Roy and Ferrara, Andrea}, biburl = {https://www.bibsonomy.org/bibtex/22cd27fcc1b167073c8a13da6494c9640/miki}, description = {[1606.02719] Cosmic reionization after Planck II: contribution from quasars}, interhash = {f24fdc251919e220660741922c61fd28}, intrahash = {2cd27fcc1b167073c8a13da6494c9640}, keywords = {agn contribution ionisation}, note = {cite arxiv:1606.02719Comment: 6 pages, 3 figures, submitted to MNRAS}, timestamp = {2016-06-10T09:43:04.000+0200}, title = {Cosmic reionization after Planck II: contribution from quasars}, url = {http://arxiv.org/abs/1606.02719}, year = 2016 }