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Probing the end of reionization with the near zones of z ≳ 6 QSOs

Keating, Laura C. ; Haehnelt, Martin G. ; Cantalupo, Sebastiano ; Puchwein, Ewald

In: Monthly Notices of the Royal Astronomical Society, 2015, vol. 454, no. 1, p. 681-697

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    Title
    • Probing the end of reionization with the near zones of z ≳ 6 QSOs
    Author
    • Keating, Laura C.. Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK
    • Haehnelt, Martin G.. Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK
    • Cantalupo, Sebastiano. Department of Physics, Institute for Astronomy, ETH Zurich, Wolfgang-Pauli-Strasse 27, CH-8093 Zurich, Switzerland
    • Puchwein, Ewald. Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK
    Document Type
    • Postprint
    Language
    • English
    Published in
    • Monthly Notices of the Royal Astronomical Society, 2015, vol. 454, no. 1, p. 681-697. Oxford University Press
    Other Version
    OAI-PMH Identifier
    • oai:doc.rero.ch:294055
    Summary
    QSO near zones are an important probe of the ionization state of the intergalactic medium (IGM) at z ∼ 6-7, at the end of reionization. We present here high-resolution cosmological 3D radiative transfer simulations of QSO environments for a wide range of host halo masses, 1010-12.5 M⊙. Our simulated near zones reproduce both the overall decrease of observed near-zone sizes at 6 < z < 7 and their scatter. The observable near-zone properties in our simulations depend only very weakly on the mass of the host halo. The size of the H ii region expanding into the IGM is generally limited by (super-)Lyman Limit systems loosely associated with (low-mass) dark matter haloes. This leads to a strong dependence of near-zone size on direction and drives the large observed scatter. In the simulation centred on our most massive host halo, many sightlines show strong red damping wings even for initial volume averaged neutral hydrogen fractions as low as ∼10−3. For QSO lifetimes long enough to allow growth of the central supermassive black hole while optically bright, we can reproduce the observed near zone of ULAS J1120+0641 only with an IGM that is initially neutral. Our results suggest that larger samples of z > 7 QSOs will provide important constraints on the evolution of the neutral hydrogen fraction and thus on how late reionization ends