Large fluctuations in the hydrogen-ionizing background and mean free path following the epoch of reionization

2015/09/23 by Frederick B. Davies, Steven R. Furlanetto · 1 citation
Physics and Astronomy · #Astrophysics #Astrophysics and Cosmic Phenomena #Extrapolation #Galaxies: Formation, Evolution, Phenomena #Galaxy #Intergalactic medium #Ionizing radiation #Irradiation #Lyman-alpha forest #Mean free path #Nuclear physics #Opacity #Optics #Physics #Population #Radio Astronomy Observations and Technology #Redshift #Reionization #Scattering #Statistics #astro-ph.CO

paper · pdf · doi:10.1093/mnras/stw931

13 pages, 11 figures, submitted to MNRAS

arxiv created 2015/09/23 · openalex publication_date 2016/04/22 · arxiv updated 2016/04/27 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05

Abstract

Extremely large opaque troughs in the Lyα forest have been interpreted as a sign of an extended reionization process below z ∼ 6. Such features are impossible to reproduce with simple models of the intergalactic ionizing background that assume a uniform mean free path of ionizing photons. We build a self-consistent model of the ionizing background that includes fluctuations in the mean free path due to the varying strength of the ionizing background and large-scale density field. The dominant effect is the suppression of the ionizing background in large-scale voids due to ‘self-shielding’ by an enhanced number of optically thick absorbers. Our model results in a distribution of 50 Mpc h−1 Lyα forest effective optical depths that significantly improves agreement with the observations at z ∼ 5.6. Extrapolation to z ∼ 5.4 and 5.8 appears promising, but matching the mean background evolution requires evolution in the absorber population beyond the scope of the present model. We also demonstrate the need for extremely large volumes (>400 Mpc on a side) to accurately determine the incidence of rare large-scale features in the Lyα forest.

Citations

• A Survey of [CLC][ITAL]z[/ITAL][/CLC] > 5.8 Quasars in the Sloan Digital Sky Survey. I. Discovery of Three New Quasars and the Spatial Density of Luminous Quasars at [CLC][ITAL]z[/ITAL][/CLC] ∼ 6
• Hubble Flow Broadening Of The Lyman-alpha Forest And Its Implications
• Constraining the topology of reionization through Lyα absorption
• Cosmic Variance in the Transparency of the Intergalactic Medium after Reionization
• The Birth of a Galaxy - III. Propelling reionisation with the faintest galaxies
• Physical effects on the Lyα forest flux power spectrum: damping wings, ionizing radiation fluctuations and galactic winds
• The inhomogeneous ionizing background following reionization
• THE EVOLUTION OF LYMAN LIMIT ABSORPTION SYSTEMS TO REDSHIFT SIX
• Reionization of the Intergalactic Medium and the Damping Wing of the Gunn‐Peterson Trough
• NINE-YEAR WILKINSON MICROWAVE ANISOTROPY PROBE ( WMAP ) OBSERVATIONS: COSMOLOGICAL PARAMETER RESULTS
• Probing reionization with Lyman α emission lines
• Resolving the high redshift Lyα forest in smoothed particle hydrodynamics simulations
• The observed ionization rate of the intergalactic medium and the ionizing emissivity at z >= 5: evidence for a photon-starved and extended epoch of reionization
• Was reionization complete by z∼ 5-6?
• The Giant Gemini GMOS survey of zem > 4.4 quasars – I. Measuring the mean free path across cosmic time
• Smoothed Particle Hydrodynamics
• Calibrating cosmological radiative transfer simulations with Lyman alpha forest data: Evidence for large spatial UV background fluctuations at z ~ 5.6 - 5.8 due to rare bright sources

Cited by

• On the accuracy of common moment-based radiative transfer methods for simulating reionization