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The host haloes of O I absorbers in the reionization epoch

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  • Kristian Finlator
  • Joseph A. Muñoz
  • B. D. Oppenheimer
  • S. Peng Oh
  • Feryal Özel
  • Romeel Davé

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Original languageEnglish
Pages (from-to)1818-1835
JournalMonthly Notices of the Royal Astronomical Society
Issue number2
Publication statusPublished - 1 Oct 2013


We use a radiation hydrodynamic simulation of the hydrogen reionization epoch to study O I absorbers at z ˜ 6. The intergalactic medium (IGM) is reionized before it is enriched; hence, O I absorption originates within dark matter haloes. The predicted abundance of O I absorbers is in reasonable agreement with observations. At z = 10, ≈70 per cent of sightlines through atomically cooled haloes encounter a visible (NOI > 1014cm-2) column. Reionization ionizes and removes gas from haloes less massive than 108.4 M⊙, but 20 per cent of sightlines through more massive haloes encounter visible columns even at z = 5. The mass scale of absorber host haloes is 10-100 times smaller than the haloes of Lyman-break galaxies and Lyman α emitters, hence absorption probes the dominant ionizing sources more directly. O I absorbers have neutral hydrogen columns of 1019-1021 cm-2, suggesting a close resemblance between objects selected in O I and H I absorption. Finally, the absorption in the foreground of the z = 7.085 quasar ULAS J1120+0641 cannot originate in a dark matter halo because halo gas at the observed H I column density is enriched enough to violate the upper limits on the O I column. By contrast, gas at less than one-third the cosmic mean density satisfies the constraints. Hence, the foreground absorption likely originates in the IGM.

    Research areas

  • galaxies: evolution, galaxies: formation, galaxies: haloes, galaxies: high-redshift, quasars: absorption lines, cosmology: theory

ID: 57685855