Large Lyman-$\alpha$ opacity fluctuations and low CMB $\tau$ in models of late reionization with large islands of neutral hydrogen extending to z<5.5 - Archive ouverte HAL Accéder directement au contenu
Article Dans Une Revue Monthly Notices of the Royal Astronomical Society Année : 2019

Large Lyman-$\alpha$ opacity fluctuations and low CMB $\tau$ in models of late reionization with large islands of neutral hydrogen extending to z<5.5

Girish Kulkarni
  • Fonction : Auteur
Laura C. Keating
  • Fonction : Auteur
Martin G. Haehnelt
  • Fonction : Auteur
Sarah E.I. Bosman
  • Fonction : Auteur
Ewald Puchwein

Résumé

High-redshift quasi-stellar object (QSO) spectra show large spatial fluctuations in the Ly α opacity of the intergalactic medium on surprisingly large scales at |$z$| ≳ 5.5. We present a radiative transfer simulation of cosmic reionization driven by galaxies that reproduces this large scatter and the rapid evolution of the Ly α opacity distribution at 5 < |$z$| < 6. The simulation also reproduces the low Thomson scattering optical depth reported by the latest cosmic microwave background (CMB) measurement and is consistent with the observed short near-zones and strong red damping wings in the highest redshift QSOs. It also matches the rapid disappearance of observed Ly α emission by galaxies at |$z$| ≳ 6. Reionization is complete at |$z$| = 5.3 in our model, and 50 per cent of the volume of the Universe is ionized at |$z$| = 7. Agreement with the Ly α forest data in such a late reionization model requires a rapid evolution of the ionizing emissivity of galaxies that peaks at |$z$| ∼ 6.8. The late end of reionization results in a large scatter in the photoionization rate and the neutral hydrogen fraction at redshifts as low as |$z$| ≲ 5.5 with large residual neutral ‘islands’ that can produce very long Gunn–Peterson troughs resembling those seen in the data.
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Dates et versions

hal-01891216 , version 1 (30-06-2023)

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Girish Kulkarni, Laura C. Keating, Martin G. Haehnelt, Sarah E.I. Bosman, Ewald Puchwein, et al.. Large Lyman-$\alpha$ opacity fluctuations and low CMB $\tau$ in models of late reionization with large islands of neutral hydrogen extending to z<5.5. Monthly Notices of the Royal Astronomical Society, 2019, 485 (1), pp.L24-L28. ⟨10.1093/mnrasl/slz025⟩. ⟨hal-01891216⟩
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