No evidence for a significant AGN contribution to cosmic hydrogen
reionization
S. Parsa, J. Dunlop, и R. McLure. (2017)cite arxiv:1704.07750Comment: 20 pages, 8 figures, submitted to MNRAS.
Аннотация
We reinvestigate a claimed sample of 22 X-ray detected active galactic nuclei
(AGN) at redshifts z > 4, which has reignited the debate as to whether young
galaxies or AGN reionized the Universe. These sources lie within the
GOODS-S/CANDELS field, and we examine both the robustness of the claimed X-ray
detections (within the Chandra 4Ms imaging) and perform an independent analysis
of the photometric redshifts of the optical/infrared counterparts. We confirm
the reality of only 15 of the 22 reported X-ray detections, and moreover find
that only 12 of the 22 optical/infrared counterpart galaxies actually lie
robustly at z > 4. Combining these results we find convincing evidence for only
7 X-ray AGN at z > 4 in the GOODS-S field, of which only one lies at z > 5. We
recalculate the evolving far-UV (1500 Angstrom) luminosity density produced by
AGN at high redshift, and find that it declines rapidly from z = 4 to z = 6, in
agreement with several other recent studies of the evolving AGN luminosity
function. The associated rapid decline in inferred hydrogen-ionizing emissivity
contributed by AGN falls an order-of-magnitude short of the level required to
maintain hydrogen ionization at z ~ 6. We conclude that all available evidence
continues to favour a scenario in which young galaxies reionized the Universe,
with AGN making, at most, a very minor contribution to cosmic hydrogen
reionization.
Описание
[1704.07750] No evidence for a significant AGN contribution to cosmic hydrogen reionization
%0 Generic
%1 parsa2017evidence
%A Parsa, S.
%A Dunlop, J. S.
%A McLure, R. J.
%D 2017
%K AGN high-redshift reionization
%T No evidence for a significant AGN contribution to cosmic hydrogen
reionization
%U http://arxiv.org/abs/1704.07750
%X We reinvestigate a claimed sample of 22 X-ray detected active galactic nuclei
(AGN) at redshifts z > 4, which has reignited the debate as to whether young
galaxies or AGN reionized the Universe. These sources lie within the
GOODS-S/CANDELS field, and we examine both the robustness of the claimed X-ray
detections (within the Chandra 4Ms imaging) and perform an independent analysis
of the photometric redshifts of the optical/infrared counterparts. We confirm
the reality of only 15 of the 22 reported X-ray detections, and moreover find
that only 12 of the 22 optical/infrared counterpart galaxies actually lie
robustly at z > 4. Combining these results we find convincing evidence for only
7 X-ray AGN at z > 4 in the GOODS-S field, of which only one lies at z > 5. We
recalculate the evolving far-UV (1500 Angstrom) luminosity density produced by
AGN at high redshift, and find that it declines rapidly from z = 4 to z = 6, in
agreement with several other recent studies of the evolving AGN luminosity
function. The associated rapid decline in inferred hydrogen-ionizing emissivity
contributed by AGN falls an order-of-magnitude short of the level required to
maintain hydrogen ionization at z ~ 6. We conclude that all available evidence
continues to favour a scenario in which young galaxies reionized the Universe,
with AGN making, at most, a very minor contribution to cosmic hydrogen
reionization.
@misc{parsa2017evidence,
abstract = {We reinvestigate a claimed sample of 22 X-ray detected active galactic nuclei
(AGN) at redshifts z > 4, which has reignited the debate as to whether young
galaxies or AGN reionized the Universe. These sources lie within the
GOODS-S/CANDELS field, and we examine both the robustness of the claimed X-ray
detections (within the Chandra 4Ms imaging) and perform an independent analysis
of the photometric redshifts of the optical/infrared counterparts. We confirm
the reality of only 15 of the 22 reported X-ray detections, and moreover find
that only 12 of the 22 optical/infrared counterpart galaxies actually lie
robustly at z > 4. Combining these results we find convincing evidence for only
7 X-ray AGN at z > 4 in the GOODS-S field, of which only one lies at z > 5. We
recalculate the evolving far-UV (1500 Angstrom) luminosity density produced by
AGN at high redshift, and find that it declines rapidly from z = 4 to z = 6, in
agreement with several other recent studies of the evolving AGN luminosity
function. The associated rapid decline in inferred hydrogen-ionizing emissivity
contributed by AGN falls an order-of-magnitude short of the level required to
maintain hydrogen ionization at z ~ 6. We conclude that all available evidence
continues to favour a scenario in which young galaxies reionized the Universe,
with AGN making, at most, a very minor contribution to cosmic hydrogen
reionization.},
added-at = {2017-04-26T10:03:20.000+0200},
author = {Parsa, S. and Dunlop, J. S. and McLure, R. J.},
biburl = {https://www.bibsonomy.org/bibtex/285f4753095fb4112e774f53f407828b3/miki},
description = {[1704.07750] No evidence for a significant AGN contribution to cosmic hydrogen reionization},
interhash = {60267de13b91ee8f34d51d3621463cde},
intrahash = {85f4753095fb4112e774f53f407828b3},
keywords = {AGN high-redshift reionization},
note = {cite arxiv:1704.07750Comment: 20 pages, 8 figures, submitted to MNRAS},
timestamp = {2017-04-26T10:03:20.000+0200},
title = {No evidence for a significant AGN contribution to cosmic hydrogen
reionization},
url = {http://arxiv.org/abs/1704.07750},
year = 2017
}