Detecting the 21 cm Forest in the 21 cm Power Spectrum

Abstract

We describe a new technique for constraining the radio loud population of active galactic nuclei at high redshift by measuring the imprint of 21 cm spectral absorption features (the 21 cm forest) on the 21 cm power spectrum. Using semi-numerical simulations of the intergalactic medium and a semi-empirical source population we show that the 21 cm forest dominates a distinctive region of $k$-space, $k\gtrsim 0.5{\text{Mpc}}^{-1}$. By simulating foregrounds and noise for current and potential radio arrays, we find that a next generation instrument with a collecting area on the order of $\sim 0.1{\text{km}}^2$ (such as the Hydrogen Epoch of Reionization Array) may separately constrain the X-ray heating history at large spatial scales and radio loud active galactic nuclei of the model we study at small ones. We extrapolate our detectability predictions for a single radio loud active galactic nuclei population to arbitrary source scenarios by analytically relating the 21 cm forest power spectrum to the optical depth power spectrum and an integral over the radio luminosity function.

20 pages, 17 figures, accepted for publication in MNRAS

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• First Limits on the 21 cm Power Spectrum during the Epoch of X-ray heating
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• Imprints of quasar duty cycle on the 21cm signal from the Epoch of Reionization
• The 21-cm forest as a simultaneous probe of dark matter and cosmic heating history
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• Simulating the 21cm forest detectable with LOFAR and SKA in the spectra of high-z GRBs
• The detectability of strong 21 centimetre forest absorbers from the diffuse intergalactic medium in late reionisation models
• Statistical Detection of IGM Structures during Cosmic Reionization using Absorption of the Redshifted 21 cm line by HI against Compact Background Radio Sources
• Analyzing the 21cm forest with Wavelet Scattering Transform: Insight into non-Gaussian features of 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
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• It's Always Darkest Before the Cosmic Dawn: Early Results from Novel Tools and Telescopes for 21 cm Cosmology