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The detectability of strong 21-cm forest absorbers from the diffuse intergalactic medium in late reionization models

Accepted version
Peer-reviewed

Type

Article

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Authors

Šoltinský, T 
Bolton, JS 
Hatch, N 
Haehnelt, MG 
Keating, LC 

Abstract

A late end to reionisation at redshift z≃5.3 is consistent with observed spatial variations in the Lyα forest transmission and the deficit of Lyα emitting galaxies around extended Lyα absorption troughs at z=5.5. In this model, large islands of neutral hydrogen should persist in the diffuse intergalactic medium (IGM) until z≃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 τ21>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 TK≃102K, we find that strong 21 cm forest absorption lines should persist until z=6. For a sample of ∼10 sufficiently radio loud background sources, a null-detection of 21 cm forest absorbers at z≃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.

Description

Keywords

methods: numerical, intergalactic medium, quasars: absorption lines, dark ages, reionization, first stars

Journal Title

Monthly Notices of the Royal Astronomical Society

Conference Name

Journal ISSN

0035-8711
1365-2966

Volume Title

506

Publisher

Oxford University Press (OUP)

Rights

All rights reserved
Sponsorship
Science and Technology Facilities Council (ST/S000623/1)
Science and Technology Facilities Council (ST/M007065/1)
STFC (ST/M007073/1)
Science and Technology Facilities Council (ST/N000927/1)
Science and Technology Facilities Council (ST/R002452/1)
Science and Technology Facilities Council (ST/R00689X/1)