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.
Description
[1606.02719] Cosmic reionization after Planck II: contribution from quasars
%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
}