The detectability of strong 21 centimetre forest absorbers from the diffuse intergalactic medium in late reionisation models

Abstract

A late end to reionisation at redshift $z\simeq 5.3$ is consistent with observed spatial variations in the Ly$\alpha$ forest transmission and the deficit of Ly$\alpha$ emitting galaxies around extended Ly$\alpha$ absorption troughs at $z=5.5$. In this model, large islands of neutral hydrogen should persist in the diffuse intergalactic medium (IGM) until $z\simeq 6$. We use a novel, hybrid approach that combines high resolution cosmological hydrodynamical simulations with radiative transfer to predict the incidence of strong 21 cm forest absorbers with optical depths ${\tau }_{21}>10^{-2}$ from the diffuse IGM in these late reionisation models. We include the effect of redshift space distortions on the simulated 21 cm forest spectra, and treat the highly uncertain heating of the pre-reionisation IGM by soft X-rays as a free parameter. For a model with only modest IGM pre-heating, such that average gas kinetic temperatures in the diffuse IGM remain below $T_{\mathrm{K}}\simeq 10^2\mathrm{K}$, we find that strong 21 cm forest absorption lines should persist until $z=6$. For a sample of $\sim 10$ sufficiently radio loud background sources, a null-detection of 21 cm forest absorbers at $z\simeq 6$ with SKA1-low or possibly LOFAR should provide an informative lower limit on the still largely unconstrained soft X-ray background at high redshift and the temperature of the pre-reionisation IGM.

18 pages, 11 figures, 4 tables. Accepted for publication in MNRAS

References in corpus (33)

• Cosmology at Low Frequencies: The 21 cm Transition and the High-Redshift Universe
• The LOFAR Two-metre Sky Survey - I. Survey Description and Preliminary Data Release
• Model-independent evidence in favor of an end to reionization by z~6
• Evidence of patchy hydrogen reionization from an extreme Ly$\alpha$ trough below redshift six
• Pōniuā'ena: A Luminous $z=7.5$ Quasar Hosting a 1.5 Billion Solar Mass Black Hole
• Improved upper limits on the 21-cm signal power spectrum of neutral hydrogen at $\mathbf{z}\approx 9.1$ from LOFAR
• The Global 21 Centimeter Background from High Redshifts
• 21 cm fluctuations from inhomogeneous X-ray heating before reionization
• Inferences on the Timeline of Reionization at z~8 From the KMOS Lens-Amplified Spectroscopic Survey
• Deep multi-redshift limits on Epoch of Reionisation 21cm Power Spectra from Four Seasons of Murchison Widefield Array Observations
• The CMBR fluctuations from HI perturbations prior to reionization
• The nature and evolution of the highly ionized near-zones in the absorption spectra of z~6 quasars
• A radiative transfer scheme for cosmological reionization based on a local Eddington tensor
• The LOFAR Two Metre Sky Survey: Deep Fields Data Release 1 -- III. Host-galaxy identifications and value added catalogues
• Quasar Proximity Zones and Patchy Reionization
• Constraining the intergalactic medium at $z\approx$ 9.1 using LOFAR Epoch of Reionization observations
• Anticipated Performance of the Square Kilometre Array -- Phase 1 (SKA1)
• The Chandra COSMOS legacy survey: Energy Spectrum of the Cosmic X-ray Background and constraints on undetected populations
• The PHLEK Survey: A New Determination of the Primordial Helium Abundance
• Decoding the X-ray Properties of Pre-Reionization Era Sources
• The Scattering of Lyman-series Photons in the Intergalactic Medium
• Spin Exchange Rates in Electron-Hydrogen Collisions
• Modelling the observed luminosity function and clustering evolution of Lyman-$\alpha$ emitters: growing evidence for late reionization
• Heating and cooling of the intergalactic medium by resonance photons
• Spin Exchange Rates in Proton-Hydrogen Collisions
• Modelling the luminosities and sizes of radio galaxies: radio luminosity function at z = 6
• Radio Detection of VIK J2318$-$3113, the Most Distant Radio-Loud Quasar ($z$=6.44)
• The broadening of Lyman-alpha forest absorption lines
• The earliest galaxies seen in 21 cm line absorption
• Lyalpha heating and its impact on early structure formation
• The influence of metagalactic ultra-violet background fluctuations on the high-redshift Ly$\alpha$ forest
• The WEAVE-LOFAR Survey
• Statistical Detection of IGM Structures during Cosmic Reionization using Absorption of the Redshifted 21 cm line by HI against Compact Background Radio Sources

Cited by in corpus (1)

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