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Accepted manuscript

Percent-level timing of reionization: self-consistent, implicit-likelihood inference from XQR-30+ Lyα forest data

Published online by Cambridge University Press:  14 April 2025

Yuxiang Qin Open the ORCID record for Yuxiang Qin [Opens in a new window] ,
Andrei Mesinger ,
David Prelogović ,
George Becker ,
Manuela Bischetti ,
Sarah E. I. Bosman ,
Frederick B. Davies ,
Valentina D’Odorico ,
Prakash Gaikwad  and
Martin G. Haehnelt
...Show all authors
Yuxiang Qin*
Affiliation:
Research School of Astronomy and Astrophysics, Australian National University, Canberra, ACT 2611, Australia ARC Centre of Excellence for All Sky Astrophysics in 3 Dimensions (ASTRO 3D), Australia
Andrei Mesinger
Affiliation:
Scuola Normale Superiore, Piazza dei Cavalieri 7, 56125 Pisa, Italy
David Prelogović
Affiliation:
Scuola Normale Superiore, Piazza dei Cavalieri 7, 56125 Pisa, Italy Scuola Internazionale Superiore di Studi Avanzati (SISSA), Via Bonomea 265, 34136 Trieste, Italy
George Becker
Affiliation:
Department of Physics & Astronomy, University of California, Riverside, CA 92521, USA
Manuela Bischetti
Affiliation:
Dipartimento di Fisica, Universitá di Trieste, Sezione di Astronomia, Via G.B. Tiepolo 11, I-34131 Trieste, Italy INAF - Osservatorio Astronomico di Trieste, Via G. B. Tiepolo 11, I–34131 Trieste, Italy
Sarah E. I. Bosman
Affiliation:
Institute for Theoretical Physics, Heidelberg University, Philosophenweg 12, D–69120, Heidelberg, Germany Max-Planck-Institut für Astronomie, Königstuhl 17, D-69117 Heidelberg, Germany
Frederick B. Davies
Affiliation:
Max-Planck-Institut für Astronomie, Königstuhl 17, D-69117 Heidelberg, Germany
Valentina D’Odorico
Affiliation:
Scuola Normale Superiore, Piazza dei Cavalieri 7, 56125 Pisa, Italy INAF - Osservatorio Astronomico di Trieste, Via G. B. Tiepolo 11, I–34143 Trieste, Italy
Prakash Gaikwad
Affiliation:
Max-Planck-Institut für Astronomie, Königstuhl 17, D-69117 Heidelberg, Germany
Martin G. Haehnelt
Affiliation:
Kavli Institute for Cosmology and Institute of Astronomy, Madingley Road, Cambridge, CB3 0HA, UK
Laura Keating
Affiliation:
Institute for Astronomy, University of Edinburgh, Blackford Hill, Edinburgh, EH9 3HJ, UK
Samuel Lai
Affiliation:
Commonwealth Scientific and Industrial Research Organisation (CSIRO), Space & Astronomy, P. O. Box 1130, Bentley, WA 6102, Australia
Emma Ryan-Weber
Affiliation:
ARC Centre of Excellence for All Sky Astrophysics in 3 Dimensions (ASTRO 3D), Australia Centre for Astrophysics and Supercomputing, Swinburne University of Technology, Hawthorn, Victoria 3122, Australia
Sindhu Satyavolu
Affiliation:
Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai 400005, India Institut de Física d’Altes Energies (IFAE), The Barcelona Institute of Science and Technology, Campus UAB, 08193 Bellaterra Barcelona, Spain
Fabian Walter
Affiliation:
Max-Planck-Institut für Astronomie, Königstuhl 17, D-69117 Heidelberg, Germany National Radio Astronomy Observatory, Pete V. Domenici Array Science Center, P.O. Box O, Socorro, NM 87801, USA
Yongda Zhu
Affiliation:
Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721, USA
*
Author for correspondence: Y. Qin, Email: [email protected].
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Abstract

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The Lyman alpha (Lyα) forest in the spectra of z > 5 quasars provides a powerful probe of the late stages of the Epoch of Reionization (EoR).With the recent advent of exquisite datasets such as XQR-30, many models have struggled to reproduce the observed large-scale fluctuations in the Lyα opacity. Here we introduce a Bayesian analysis framework that forward-models large-scale lightcones of intergalactic medium (IGM) properties, and accounts for unresolved sub-structure in the Lyα opacity by calibrating to higher-resolution hydrodynamic simulations. Our models directly connect physically-intuitive galaxy properties with the corresponding IGM evolution, without having to tune “effective” parameters or calibrate out the mean transmission. The forest data, in combination with UV luminosity functions and the CMB optical depth, are able to constrain global IGM properties at percent level precision in our fiducial model. Unlike many other works, we recover the forest observations without invoking a rapid drop in the ionizing emissivity from z ∼ 7 to 5.5, which we attribute to our sub-grid model for recombinations. In this fiducial model, reionization ends at z = 5.44 ± 0.02 and the EoR mid-point is at z = 7.7 ± 0.1. The ionizing escape fraction increases towards faint galaxies, showing a mild redshift evolution at fixed UV magnitude, MUV. Half of the ionizing photons are provided by galaxies fainter than MUV ∼ –12, well below direct detection limits of optical/NIR instruments including JWST. We also show results from an alternative galaxy model that does not allow for a redshift evolution in the ionizing escape fraction. Despite being decisively disfavored by the Bayesian evidence, the posterior of this model is in qualitative agreement with that from our fiducial model. We caution however that our conclusions regarding the early stages of the EoR and which sources reionized the Universe are more model-dependent.

Keywords

cosmology: theorydark ages, reionization, first starsearly Universegalaxies: high-redshiftintergalactic medium
Type
Research Article
Information
Publications of the Astronomical Society of Australia , Accepted manuscript , pp. 1 - 23
Creative Commons
Creative Common License - CCCreative Common License - BY
This is an Open Access article, distributed under the terms of the Creative Commons Attribution licence (https://creativecommons.org/licenses/by/4.0/), which permits unrestricted re-use, distribution and reproduction, provided the original article is properly cited.
Copyright
© The Author(s), 2025. Published by Cambridge University Press on behalf of Astronomical Society of Australia