Detailed modelling of the 21-cm Forest

Abstract

The 21-cm forest is a promising probe of the Epoch of Reionization. The local state of the intergalactic medium (IGM) is encoded in the spectrum of a background source (radio-loud quasars or gamma ray burst afterglow) by absorption at the local 21-cm wavelength, resulting in a continuous and fluctuating absorption level. Small-scale structures (filaments and minihaloes) in the IGM are responsible for the strongest absorption features. The absorption can also be modulated on large scales by inhomogeneous heating and Wouthuysen-Field coupling. We present the results from a simulation that attempts to preserve the cosmological environment while resolving some of the small-scale structures (a few kpc resolution in a 50 Mpc/h box). The simulation couples the dynamics and the ionizing radiative transfer and includes X-ray and Lyman lines radiative transfer for a detailed physical modelling. As a result we find that soft X-ray self-shielding, Lyman-alpha self-shielding and shock heating all have an impact on the predicted values of the 21-cm optical depth of moderately overdense structures like filaments. An correct treatment of the peculiar velocities is also critical. Modelling these processes seems necessary for accurate predictions and can be done only at high enough resolution. As a result, based on our fiducial model, we estimate that LOFAR should be able to detect a few (strong) absorptions features in a frequency range of a few tens of MHz for a 20 mJy source located at z=10, while the SKA would extract a large fraction of the absorption information for the same source.

13 pages, accepted for publication in MNRAS

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• A powerful radio-loud quasar at the end of cosmic reionization
• 21SSD: a public database of simulated 21-cm signals from the epoch of reionization
• Imprints of quasar duty cycle on the 21cm signal from the Epoch of Reionization
• 21 cm Forest Constraints on Primordial Black Holes
• A unified framework for 21cm tomography sample generation and parameter inference with Progressively Growing GANs
• The detectability of strong 21 centimetre forest absorbers from the diffuse intergalactic medium in late reionisation models
• Improved upper limits on the 21-cm signal power spectrum at $z=17.0$ and $z=20.3$ from an optimal field observed with NenuFAR
• Probing quasar lifetimes with proximate $21$-centimetre absorption in the diffuse intergalactic medium at redshifts $z\ge 6$
• Analyzing the 21cm forest with Wavelet Scattering Transform: Insight into non-Gaussian features of the 21cm forest
• Impact of dark matter-baryon relative velocity on the 21cm forest
• Prospects of a statistical detection of the 21-cm forest and its potential to constrain the thermal state of the neutral IGM during reionization
• Cospatial 21 cm and metal-line absorbers in the epoch of reionization -- I : Incidence and observability
• A bubble size distribution model for the Epoch of Reionization