Distinctive rings in the 21 cm signal of the epoch of reionization

Abstract

It is predicted that sources emitting UV radiation in the Lyman band during the epoch of reionization (EoR) showed a series of discontinuities in their Ly-alpha flux radial profile as a consequence of the thickness of the Lyman line series in the primeval intergalactic medium. Through unsaturated Wouthuysen-Field coupling, these spherical discontinuities are also present in the 21 cm emission of the neutral IGM. In this article, we study the effects these discontinuities have on the differential brightness temperature of the 21 cm signal of neutral hydrogen in a realistic setting including all other sources of fluctuations. We focus on the early phases of the EoR, and we address the question of the detectability by the planned Square Kilometre Array. Such a detection would be of great interest, because these structures could provide an unambiguous diagnostic for the cosmological origin of the signal remaining after the foreground cleaning procedure. Also, they could be used as a new type of standard rulers. We determine the differential brightness temperature of the 21 cm signal in the presence of inhomogeneous Wouthuysen-Field effect using simulations which include (hydro)dynamics and both ionizing and Lyman lines 3D radiative transfer with the code LICORICE. We find that the Lyman horizons are clearly visible on the maps and radial profiles around the first sources of our simulations, but for a limited time interval, typically Δz \approx 2 at z \sim 13. Stacking the profiles of the different sources of the simulation at a given redshift results in extending this interval to Δz \approx 4. When we take into account the implementation and design planned for the SKA (collecting area, sensitivity, resolution), we find that detection will be challenging. It may be possible with a 10 km diameter for the core, but will be difficult with the currently favored design of a 5 km core.

10 pages, 10 figures; v2: Section 5.5 rewritten; some new references added; accepted for publication in Astronomy and Astrophysics

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Cited by in corpus (18)

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• Evaluating the QSO contribution to the 21-cm signal from the Cosmic Dawn
• 21SSD: a public database of simulated 21-cm signals from the epoch of reionization
• Light cone anisotropy in 21 cm signal from the epoch of reionization
• Redshift-space distortions in simulations of the 21-cm signal from the cosmic dawn
• Imprints of quasar duty cycle on the 21cm signal from the Epoch of Reionization
• Implication of the Shape of the EDGES Signal for the 21 cm Power Spectrum
• Detailed modelling of the 21-cm Forest
• A unified framework for 21cm tomography sample generation and parameter inference with Progressively Growing GANs
• Distinctive 21 cm structures of the first stars, galaxies, and quasars
• The scattering of LyA radiation in the intergalactic medium: numerical methods and solutions
• Accurate modelling of the Lyman-$\alpha$ coupling for the 21-cm signal, observability with NenuFAR and SKA
• Mapping discrete galaxies at cosmic dawn with 21-centimeter observations
• Radiative transfer of Lyman-$\alpha$ photons at cosmic dawn with realistic gas physics
• Joint Lyα emitters - quasars reionization constraints