Motivated by recent measurements of the number density of faint AGN at high
redshift, we investigate the contribution of quasars to reionization by
tracking the growth of central supermassive black holes in an update of the
Meraxes semi-analytic model. The model is calibrated against the observed
stellar mass function at $z\sim0.6-7$, the black hole mass function at
$złesssim0.5$, the global ionizing emissivity at $z\sim2-5$, and the
Thomson scattering optical depth. The model reproduces a Magorrian relation in
agreement with observations at $z<0.5$, and predicts a decreasing black hole
mass towards higher redshifts at fixed total stellar mass. With the
implementation of an opening angle of $80$ degrees for quasar radiation,
corresponding to an observable fraction of $\sim23.4$ per cent due to
obscuration by dust, the model is able to reproduce the observed quasar
luminosity function at $z\sim0.6-6$. The stellar light from galaxies
hosting faint AGN contributes a significant or dominant fraction of the UV
flux. At high redshift, the model is consistent with the bright end quasar
luminosity function and suggests that the recent faint $z\sim4$ AGN sample
compiled by Giallongo2015 includes a significant fraction of stellar
light. Direct application of this luminosity function to the calculation of AGN
ionizing emissivity consequently overestimates the number of ionizing photons
produced by quasars by a factor of 3 at $z\sim6$. We conclude that quasars
are unlikely to make a significant contribution to reionization.
Description
[1703.04895] Dark-ages Reionization and Galaxy Formation Simulation X. The small contribution of quasars to reionization
%0 Generic
%1 qin2017darkages
%A Qin, Yuxiang
%A Mutch, Simon J.
%A Poole, Gregory B.
%A Liu, Chuanwu
%A Duffy, Alan R.
%A Geil, Paul M.
%A Angel, Paul W.
%A Mesinger, Andrei
%A Wyithe, J. Stuart B.
%D 2017
%K contribution quasar reionization
%T Dark-ages Reionization and Galaxy Formation Simulation X. The small
contribution of quasars to reionization
%U http://arxiv.org/abs/1703.04895
%X Motivated by recent measurements of the number density of faint AGN at high
redshift, we investigate the contribution of quasars to reionization by
tracking the growth of central supermassive black holes in an update of the
Meraxes semi-analytic model. The model is calibrated against the observed
stellar mass function at $z\sim0.6-7$, the black hole mass function at
$złesssim0.5$, the global ionizing emissivity at $z\sim2-5$, and the
Thomson scattering optical depth. The model reproduces a Magorrian relation in
agreement with observations at $z<0.5$, and predicts a decreasing black hole
mass towards higher redshifts at fixed total stellar mass. With the
implementation of an opening angle of $80$ degrees for quasar radiation,
corresponding to an observable fraction of $\sim23.4$ per cent due to
obscuration by dust, the model is able to reproduce the observed quasar
luminosity function at $z\sim0.6-6$. The stellar light from galaxies
hosting faint AGN contributes a significant or dominant fraction of the UV
flux. At high redshift, the model is consistent with the bright end quasar
luminosity function and suggests that the recent faint $z\sim4$ AGN sample
compiled by Giallongo2015 includes a significant fraction of stellar
light. Direct application of this luminosity function to the calculation of AGN
ionizing emissivity consequently overestimates the number of ionizing photons
produced by quasars by a factor of 3 at $z\sim6$. We conclude that quasars
are unlikely to make a significant contribution to reionization.
@misc{qin2017darkages,
abstract = {Motivated by recent measurements of the number density of faint AGN at high
redshift, we investigate the contribution of quasars to reionization by
tracking the growth of central supermassive black holes in an update of the
{\sc Meraxes} semi-analytic model. The model is calibrated against the observed
stellar mass function at $z{\sim}0.6{-}7$, the black hole mass function at
$z{\lesssim}0.5$, the global ionizing emissivity at $z{\sim}2{-}5$, and the
Thomson scattering optical depth. The model reproduces a Magorrian relation in
agreement with observations at $z{<}0.5$, and predicts a decreasing black hole
mass towards higher redshifts at fixed total stellar mass. With the
implementation of an opening angle of $80$ degrees for quasar radiation,
corresponding to an observable fraction of ${\sim}23.4$ per cent due to
obscuration by dust, the model is able to reproduce the observed quasar
luminosity function at $z{\sim}0.6{-}6$. The stellar light from galaxies
hosting faint AGN contributes a significant or dominant fraction of the UV
flux. At high redshift, the model is consistent with the bright end quasar
luminosity function and suggests that the recent faint $z{\sim}4$ AGN sample
compiled by \citet{Giallongo2015} includes a significant fraction of stellar
light. Direct application of this luminosity function to the calculation of AGN
ionizing emissivity consequently overestimates the number of ionizing photons
produced by quasars by a factor of 3 at $z{\sim}6$. We conclude that quasars
are unlikely to make a significant contribution to reionization.},
added-at = {2017-03-16T11:12:57.000+0100},
author = {Qin, Yuxiang and Mutch, Simon J. and Poole, Gregory B. and Liu, Chuanwu and Duffy, Alan R. and Geil, Paul M. and Angel, Paul W. and Mesinger, Andrei and Wyithe, J. Stuart B.},
biburl = {https://www.bibsonomy.org/bibtex/24453c272756c62c34d8700f665c4427a/miki},
description = {[1703.04895] Dark-ages Reionization and Galaxy Formation Simulation X. The small contribution of quasars to reionization},
interhash = {2d2d14c02661a4e5a501cbcc58fe4f67},
intrahash = {4453c272756c62c34d8700f665c4427a},
keywords = {contribution quasar reionization},
note = {cite arxiv:1703.04895Comment: 20 pages, 11 figures, submitted to MNRAS, comments are welcome},
timestamp = {2017-03-16T11:12:57.000+0100},
title = {Dark-ages Reionization and Galaxy Formation Simulation X. The small
contribution of quasars to reionization},
url = {http://arxiv.org/abs/1703.04895},
year = 2017
}