Detecting the redshifted 21cm forest during reionization

Abstract

The 21cm forest -- HI absorption features in the spectra of high-redshift radio sources -- can potentially provide a unique probe of the largely neutral intergalactic medium (IGM) during the epoch of reionization. We present simulations of the 21cm forest due to the large scale structure of the reionization-era IGM, including a prescription for x-ray heating and the percolation of photoionization bubbles. We show that, if detected with future instruments such as the Square Kilometer Array (SKA), the 21cm forest can provide a significant constraint on the thermal history of the IGM. Detection will be aided by consideration of the sudden increase in signal variance at the onset of 21cm absorption. If radio foregrounds and the intrinsic source spectra are well understood, the flux decrement over wide bandwidths can also improve detection prospects. Our analysis accounts for the possibility of narrow absorption lines from intervening dense regions, but, unlike previous studies, our results do not depend on their properties. Assuming x-ray heating corresponding to a local stellar population, we estimate that a statistically significant detection of 21cm absorption could be made by SKA in less than a year of observing against a Cygnus A-type source at $z\sim 9$, as opposed to nearly a decade for a significant detection of the detailed forest features. We discuss observational challenges due to uncertainties regarding the abundance of background sources and the strength of the 21cm absorption signal.

Submitted to MNRAS. Revised version includes updated and extended calculations, some corrections and added references

References in corpus (14)

• Cosmology at Low Frequencies: The 21 cm Transition and the High-Redshift Universe
• The observed ionization rate of the intergalactic medium and the ionizing emissivity at z >5: Evidence for a photon starved and extended epoch of reionization
• The morphology of HII regions during reionization
• The Global 21 Centimeter Background from High Redshifts
• 21 cm fluctuations from inhomogeneous X-ray heating before reionization
• The Radio-Loud Fraction of Quasars is a Strong Function of Redshift and Optical Luminosity
• Evolution of the 21 cm signal throughout cosmic history
• Constraining the unexplored period between reionization and the dark ages with observations of the global 21 cm signal
• A Unified Catalog of Radio Objects Detected by NVSS, FIRST, WENSS, GB6, and SDSS
• Minihalo photoevaporation during cosmic reionization: evaporation times and photon consumption rates
• The Effects of Dark Matter Decay and Annihilation on the High-Redshift 21 cm Background
• Cosmic Reionization and the 21-cm signal: Comparison between an analytical model and a simulation
• Reionization constraints using Principal Component Analysis
• The 21 Centimeter Forest

Cited by in corpus (29)

• Reionization and the Cosmic Dawn with the Square Kilometre Array
• Data Analysis for Precision 21 cm Cosmology
• Signatures of X-rays in the early Universe
• Modeling the Radio Background from the First Black Holes at Cosmic Dawn: Implications for the 21 cm Absorption Amplitude
• The Epoch of Reionization
• First Limits on the 21 cm Power Spectrum during the Epoch of X-ray heating
• Discovery of a radio galaxy at z = 5.72
• Discovery of 24 radio-bright quasars at $4.9\le z\le 6.6$ using low-frequency radio observations
• Modelling the luminosities and sizes of radio galaxies: radio luminosity function at z = 6
• A search for faint high-redshift radio galaxy candidates at 150 MHz
• Detecting the 21 cm Forest in the 21 cm Power Spectrum
• 21 cm Forest Constraints on Primordial Black Holes
• Detailed modelling of the 21-cm Forest
• The 21-cm forest as a simultaneous probe of dark matter and cosmic heating history
• Stars and Reionization: The Cross-Correlation of the 21cm Line and the Near Infrared Background
• 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
• Probing quasar lifetimes with proximate $21$-centimetre absorption in the diffuse intergalactic medium at redshifts $z\ge 6$
• Prospects for Observing High-redshift Radio-loud Quasars in the SKA Era: Paving the Way for 21-cm Forest Observations
• No strong radio absorption detected in the low-frequency spectra of radio-loud quasars at z > 5.6
• 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
• Impact of dark matter-baryon relative velocity on the 21cm forest
• Prospects for measuring neutrino mass with 21-cm forest
• Signatures of particle decay in 21 cm absorptions from first minihalos
• HI absorption from the epoch of reionization and primordial magnetic fields
• Analytical modeling of the one-dimensional power spectrum of 21-cm forest based on a halo model method
• Efficient neutral-IGM inference from noisy 21-cm forest spectra with latent-space U-Net encoding and XGBoost