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An unprecedented array of new observational capabilities are starting to yield key constraints on models of the epoch of first light in the Universe. In this Letter we discuss the implications of the UV radiation background at cosmic dawn…

The prospect of detecting the first galaxies by observing their impact on the intergalactic medium as they reionized it during the first billion years leads us to ask whether such indirect observations are capable of diagnosing which types…

Cosmology and Nongalactic Astrophysics · Physics 2015-05-28 Ilian T. Iliev , Garrelt Mellema , Paul R. Shapiro , Ue-Li Pen , Yi Mao , Jun Koda , Kyungjin Ahn

At redshifts z >~ 30 neutral hydrogen gas absorbs CMB radiation at the 21cm spin-flip frequency. In principle this is observable and a high-precision probe of cosmology. We calculate the linear-theory angular power spectrum of this signal…

Astrophysics · Physics 2008-11-26 Antony Lewis , Anthony Challinor

The epoch of reionization (EoR), marking the Universe's transition from a neutral to ionized state, represents a pivotal phase for understanding the formation of the first stars and galaxies. Intensity mapping of atomic and molecular lines,…

Astrophysics of Galaxies · Physics 2025-12-17 Anirban Roy , Anthony Pullen , Patrick C. Breysse , Rachel S. Somerville

Detection and analysis of the cosmic 21 cm signal of neutral hydrogen has long been considered the most promising route towards exploration of the Epoch of Reionization (EoR). 21CMMC, a Markov Chain Monte Carlo sampler of the semi-numerical…

Cosmology and Nongalactic Astrophysics · Physics 2025-11-19 August Berklas , Jonathan Pober

At cosmic dawn, the 21-centimeter signal from intergalactic hydrogen was driven by Lyman-$\alpha$ photons from some of the earliest stars, producing a spatial pattern that reflected the distribution of galaxies at that time. Due to the…

Cosmology and Nongalactic Astrophysics · Physics 2023-11-28 Itamar Reis , Rennan Barkana , Anastasia Fialkov

After reionization, emission in the 21 cm hyperfine transition provides a direct probe of neutral hydrogen distributed in galaxies. Different from galaxy redshift surveys, observation of baryon acoustic oscillations in the cumulative 21 cm…

Cosmology and Nongalactic Astrophysics · Physics 2012-06-14 Xiao-Chun Mao

Detecting neutral hydrogen structures in the intergalactic medium (IGM) during cosmic reionization via absorption (21 cm forest) against a background radiation is considered independent and complementary to the three-dimensional tomography…

Cosmology and Nongalactic Astrophysics · Physics 2020-08-10 Nithyanandan Thyagarajan

Observations of the redshifted 21-cm signal (in absorption or emission) allow us to peek into the epoch of "dark ages" and the onset of reionization. These data can provide a novel way to learn about the nature of dark matter, in particular…

Cosmology and Nongalactic Astrophysics · Physics 2019-12-11 Alexey Boyarsky , Dmytro Iakubovskyi , Oleg Ruchayskiy , Anton Rudakovskyi , Wessel Valkenburg

We revisit the global 21cm signal calculation incorporating a possible radio background at early times, and find that the global 21cm signal shows a much stronger absorption feature, which could enhance detection prospects for future 21 cm…

Cosmology and Nongalactic Astrophysics · Physics 2018-05-23 Chang Feng , Gilbert Holder

We explore the possibility of detecting HI 21cm absorption by the neutral intergalactic medium (IGM) toward very high redshift radio sources. The epoch considered is between the time when the first ionizing sources form and when the bulk of…

Astrophysics · Physics 2016-08-30 C. Carilli , N. Y. Gnedin , F. Owen

With the advent of the first luminous sources at Cosmic Dawn (CD), the redshifted 21-cm signal, from the neutral hydrogen in the Inter-Galactic Medium (IGM), is predicted to undergo a transition from absorption to emission against the CMB.…

Cosmology and Nongalactic Astrophysics · Physics 2023-07-04 Mohd Kamran , Suman Majumdar , Raghunath Ghara , Garrelt Mellema , Somnath Bharadwaj , Jonathan R. Pritchard , Rajesh Mondal , Ilian T. Iliev

The cosmic 21-cm signal is a promising probe of the early Universe, owing to its sensitivity to the thermal state of the neutral intergalactic medium (IGM) and properties of the first luminous sources. Here, we constrain the 21-cm signal…

We use numerical hydrodynamical simulations of early structure formation in a LCDM universe to investigate the spin temperature and 21cm brightness of the diffuse intergalactic medium (IGM) prior to the epoch of cosmic reionization, at…

Astrophysics · Physics 2009-11-13 Michael Kuhlen , Piero Madau , Ryan Montgomery

We extend 21CMMC, a Monte Carlo Markov Chain sampler of 3D reionisation simulations, to perform parameter estimation directly on 3D light-cones of the cosmic 21cm signal. This brings theoretical analysis closer to the tomographic 21-cm…

Cosmology and Nongalactic Astrophysics · Physics 2018-04-11 Bradley Greig , Andrei Mesinger

A near-future detection of the 21cm signal from the epoch of reionization will provide unique opportunities to probe the underlying cosmology, provided that such cosmological information can be extracted with precision. To this end, we…

Cosmology and Nongalactic Astrophysics · Physics 2022-12-28 Wenzer Qin , Katelin Schutz , Aaron Smith , Enrico Garaldi , Rahul Kannan , Tracy R. Slatyer , Mark Vogelsberger

Using the 21 cm line, observed all-sky and across the redshift range from 0 to 5, the large scale structure of the Universe can be mapped in three dimensions. This can be accomplished by studying specific intensity with resolution ~ 10 Mpc,…

We estimate the global signal in the redshifted hyperfine structure line 21 cm of hydrogen atoms formed during the Dark Ages and Cosmic Dawn epochs. The evolution of the brightness temperature in this line was computed to study its…

Cosmology and Nongalactic Astrophysics · Physics 2025-04-11 Bohdan Novosyadlyj , Yurii Kulinich , Danylo Koval

We estimate the signal from large scale structure at high redshifts in redshifted 21cm line. We focus on z ~ 3 and the LCDM cosmology. We assume that neutral hydrogen is to be found only in galaxies, and normalise the total content to the…

Astrophysics · Physics 2009-08-18 J. S. Bagla , Martin White

Observations of the epoch of reionization give us clues about the nature and evolution of the sources of ionizing photons, or early stars and galaxies. We present a new suite of structure formation and radiative transfer simulations from…

Cosmology and Nongalactic Astrophysics · Physics 2016-01-27 Keri L. Dixon , Ilian T. Iliev , Garrelt Mellema , Kyungjin Ahn , Paul R. Shapiro