Universität zu Köln

Garaldi, Enrico ORCID: 0000-0002-6021-7020, Compostella, Michele and Porciani, Cristiano (2019). The Goldilocks problem of the quasar contribution to reionization. Mon. Not. Roy. Astron. Soc., 483 (4). S. 5301 - 5315. OXFORD: OXFORD UNIV PRESS. ISSN 1365-2966

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Abstract

The detection of an unexpectedly large number of faint candidate quasars (QSO) at z greater than or similar to 4 has motivated Madau and Haardt to investigate a reionization scenario in which active galactic nuclei dominate the photon budget at all times. Their analytical study reveals that this picture is in agreement with the evolution of the H I volume fraction in the intergalactic medium (IGM) and the optical depth to Thomson scattering of the cosmic microwave background. We employ a suite of hydrodynamical simulations post-processed with a radiative transfer code to further investigate the properties of such a reionization history. In particular, we generate synthetic absorption-line spectra for HI and He II that we compare with observational data. Although we confirm the analytical results mentioned above, we also find that the evolution of the IGM temperature and of the He II optical depth are at odds with current observational constraints. Nevertheless, the QSO-dominated scenario presents the attractive feature that it naturally generates an inhomogeneous IGM and thus produces an extended tail at high values in the distribution function of the H I effective optical depth, in agreement with recent observations. We find tentative evidence that considering some QSO emission at redshift z greater than or similar to 5 could reconcile such observations with numerical simulations that have so far failed to reproduce this feature. Finally, we show that collecting more He II-absorption spectra at z greater than or similar to 3 and studying their distinctive characteristics will be key to precisely constraining the QSO contribution to reionization.

Item Type:	Journal Article
Creators:	Creators Email ORCID ORCID Put Code Garaldi, Enrico UNSPECIFIED orcid.org/0000-0002-6021-7020 UNSPECIFIED Compostella, Michele UNSPECIFIED UNSPECIFIED UNSPECIFIED Porciani, Cristiano UNSPECIFIED UNSPECIFIED UNSPECIFIED
URN:	urn:nbn:de:hbz:38-155102
DOI:	10.1093/mnras/sty3414
Journal or Publication Title:	Mon. Not. Roy. Astron. Soc.
Volume:	483
Number:	4
Page Range:	S. 5301 - 5315
Date:	2019
Publisher:	OXFORD UNIV PRESS
Place of Publication:	OXFORD
ISSN:	1365-2966
Language:	English
Faculty:	Unspecified
Divisions:	Unspecified
Subjects:	no entry
Uncontrolled Keywords:	Keywords Language LY-ALPHA FOREST; ADAPTIVE MESH REFINEMENT; ACTIVE GALACTIC NUCLEI; HE II REIONIZATION; LINE-OF-SIGHT; INTERGALACTIC MEDIUM; GALAXY FORMATION; THERMAL HISTORY; HYDROGEN REIONIZATION; COSMIC REIONIZATION Multiple languages Astronomy & Astrophysics Multiple languages
Refereed:	Yes
URI:	http://kups.ub.uni-koeln.de/id/eprint/15510