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

Šoltinsky, Tomáš; Bolton, James S.; Hatch, Nina; Haehnelt, Martin G.; Keating, Laura C.; Kulkarni, Girish; Puchwein, Ewald; Chardin, Jonathan; Aubert, Dominique

Abstract

A late end to reionization at redshift z 5.3 is consistent with observed spatial variations in the Ly α forest transmission and the deficit of Ly α emitting galaxies around extended Ly α 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 τ 21 > 10−2 from the diffuse IGM in these late reionization 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 reionization 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 102 K, 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-reionization IGM.

Citation

Šoltinsky, T., Bolton, J. S., Hatch, N., Haehnelt, M. G., Keating, L. C., Kulkarni, G., Puchwein, E., Chardin, J., & Aubert, D. (2021). The detectability of strong 21-cm forest absorbers from the diffuse intergalactic medium in late reionization models. Monthly Notices of the Royal Astronomical Society, 506(4), 5818-5835. https://doi.org/10.1093/mnras/stab1830

• Journal Article Type: Article
• Acceptance Date: Jun 24, 2021
• Online Publication Date: Jul 1, 2021
• Publication Date: 2021-10
• Deposit Date: Jul 16, 2021
• Publicly Available Date: Jul 1, 2021
• Journal: Monthly Notices of the Royal Astronomical Society
• Print ISSN: 0035-8711
• Electronic ISSN: 1365-2966
• Publisher: Oxford University Press
• Peer Reviewed: Peer Reviewed
• Volume: 506
• Issue: 4
• Pages: 5818-5835
• DOI: https://doi.org/10.1093/mnras/stab1830
• Public URL: https://nottingham-repository.worktribe.com/output/5751464
• Publisher URL: https://academic.oup.com/mnras/article/506/4/5818/6312507
• Additional Information: This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society © 2021 The Author(s); Published by Oxford University Press on behalf of Royal Astronomical Society. All rights reserved.