Prospects of a statistical detection of the 21-cm forest and its potential to constrain the thermal state of the neutral IGM during reionization

Šoltinský, Tomáš; Kulkarni, Girish; Tendulkar, Shriharsh P.; Bolton, James S.

Abstract

The 21-cm forest signal is a promising probe of the Epoch of Reionization complementary to other 21-cm line observables and Ly α forest signal. Prospects of detecting it have significantly improved in the last decade thanks to the disco very of more than 30 radio-loud quasars at these redshifts, upgrades to telescope facilities, and the notion that neutral hydrogen islands persist down to z ≲ 5 . 5. We forward-model the 21-cm forest signal using seminumerical simulations and incorporate various instrumental features to explore the potential of detecting the 21-cm forest at z = 6, both directly and statistically, with the currently available (uGMRT) and forthcoming (SKA1-low) observatories. We show that it is possible to detect the 1D power spectrum of the 21-cm forest spectrum, especially at large scales of k ≲ 8 . 5 MHz −1 with the 500 hr of the uGMRT time and k ≲ 32 . 4 MHz −1 with the SKA1-low over 50 hr if the intergalactic medium (IGM) is 25 per cent neutral and these neutral hydrogen regions have a spin temperature of ≲ 30 K. On the other hand, we infer that a null-detection of the signal with such observations of 10 radio-loud sources at z ≈ 6 can be translated into constraints on the thermal and ionization state of the IGM which are tighter than the currently available measurements. Moreover, a null-detection of the 1D 21-cm forest power spectrum with only 50 hr of the uGMRT observations of 10 radio-loud sources can already be competitive with the Ly α forest and 21-cm tomographic observations in disfavouring models of significantly neutral and cold IGM at z = 6.

Citation

Šoltinský, T., Kulkarni, G., Tendulkar, S. P., & Bolton, J. S. (2025). Prospects of a statistical detection of the 21-cm forest and its potential to constrain the thermal state of the neutral IGM during reionization. Monthly Notices of the Royal Astronomical Society, 537(1), 364-378. https://doi.org/10.1093/mnras/staf026

• Journal Article Type: Article
• Acceptance Date: Jan 3, 2025
• Online Publication Date: Jan 8, 2025
• Publication Date: 2025-02
• Deposit Date: Jan 27, 2025
• 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: 537
• Issue: 1
• Pages: 364-378
• DOI: https://doi.org/10.1093/mnras/staf026
• Keywords: methods, numerical, intergalactic medium, quasars: absorption lines, dark ages, reionization, first stars
• Public URL: https://nottingham-repository.worktribe.com/output/43088008
• Publisher URL: https://academic.oup.com/mnras/article/537/1/364/7945802