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The dark age of the universe, when no luminous object had existed, ended with the birth of the first stars, galaxies, and blackholes. This epoch is called cosmic dawn. Cosmic reionization is the major transition of the intergalactic medium…

Cosmology and Nongalactic Astrophysics · Physics 2023-03-21 Hayato Shimabukuro , Kenji Hasegawa , Akira Kuchinomachi , Hidenobu Yajima , Shintaro Yoshiura

The 21cm line of neutral hydrogen (HI) opens a new avenue in our exploration of the structure and evolution of the Universe. It provides complementary data to the current large-scale structure observations with different systematics, and…

We report the first direct detection of the cosmological power spectrum using the intensity signal from 21-cm emission of neutral hydrogen (HI), derived from interferometric observations with the L-band receivers of the new MeerKAT radio…

Cosmology and Nongalactic Astrophysics · Physics 2023-01-31 Sourabh Paul , Mario G. Santos , Zhaoting Chen , Laura Wolz

We investigate a number of potential foregrounds for an ambitious goal of future radio telescopes such as the Square Kilometer Array (SKA) and Low Frequency Array (LOFAR): spatial tomography of neutral gas at high redshift in 21cm emission.…

Astrophysics · Physics 2009-11-07 S. Peng Oh , Katherine J. Mack

A number of radio interferometers are currently being planned or constructed to observe 21 cm emission from reionization. Not only will such measurements provide a detailed view of that epoch, but, since the 21 cm emission also traces the…

Studies of the cosmic dark ages ($30 \lesssim z \lesssim 150$) using the highly redshifted 21 cm line of neutral hydrogen offer unparalleled amounts of cosmological information, and recent years have seen the refinement of concepts for such…

Cosmology and Nongalactic Astrophysics · Physics 2025-08-01 Jonathan C. Pober , Willow Smith

The distribution of 21 cm emission from neutral hydrogen is a powerful cosmological and astrophysical probe, as it traces the underlying dark matter and cold gas distributions throughout cosmic times. However, the prediction of observable…

Cosmology and Nongalactic Astrophysics · Physics 2026-05-22 Satvik Mishra , Roberto Trotta , Matteo Viel

Upcoming experiments such as Hydrogen Epoch of Reionization Array (HERA) and Square Kilometre Array (SKA) are intended to measure the 21cm signal over a wide range of redshifts, representing an incredible opportunity in advancing our…

Cosmology and Nongalactic Astrophysics · Physics 2020-05-06 Héctor J. Hortúa , Riccardo Volpi , Luigi Malagò

We study the prospects for extracting detailed statistical properties of the neutral Hydrogen distribution during the era of reionization using the brightness temperature fluctuations from redshifted 21 cm line emission. Detection of this…

Astrophysics · Physics 2009-11-10 M. G. Santos , A. Cooray , L. Knox

21cm emission from residual neutral hydrogen after the epoch of reionization can be used to trace the cosmological power spectrum of density fluctuations. Using a Fisher matrix formulation, we provide a detailed forecast of the constraints…

Astrophysics · Physics 2009-11-13 Eli Visbal , Abraham Loeb , Stuart Wyithe

We detail the the REACH radiometric system designed to enable measurements of the 21-cm neutral hydrogen line. Included is the radiometer architecture and end-to-end system simulations as well as a discussion of the challenges intrinsic to…

Understanding the formation and evolution of the first stars and galaxies represents one of the most exciting frontiers in astronomy. Since the universe was filled with hydrogen atoms at early times, the most promising probe of the epoch of…

Cosmology and Nongalactic Astrophysics · Physics 2016-08-24 Rennan Barkana

Upper limits from the current generation of interferometers targeting the 21-cm signal from high redshifts have recently begun to rule out physically realistic, though still extreme, models of the Epoch of Reionization (EoR). While…

Cosmology and Nongalactic Astrophysics · Physics 2022-06-08 Jordan Mirocha , Julian B. Muñoz , Steven R. Furlanetto , Adrian Liu , Andrei Mesinger

The redshifted 21 cm line, arising from neutral hydrogen, offers a unique probe into the intergalactic medium and the first stars and galaxies formed in the early universe. However, detecting this signal is a challenging task because of…

Instrumentation and Methods for Astrophysics · Physics 2025-10-09 Shijie Sun , Jiaqin Xu , Minquan Zhou , Shenzhe Xu , Fengquan Wu , Haoran Zhang , Juyong Zhang , Bin Ma , Zhaohui Shang , Xuelei Chen

This study presents the methodology for creating a cost-efficient radio astronomy telescope that can be used to detect 21 cm emissions (1420.405 MHz) and determine the distribution and kinematics of neutral hydrogen specifically in the…

Instrumentation and Methods for Astrophysics · Physics 2024-11-04 Jack Phelps

The emission of 21-cm radiation from a neutral intergalactic medium (IGM) at high redshift is discussed in connection with the thermal and ionization history of the universe. The physical mechanisms that make such radiation detectable…

Astrophysics · Physics 2009-10-31 Paolo Tozzi , Piero Madau , Avery Meiksin , Martin J. Rees

Studying the cosmic dawn and the epoch of reionization through the redshifted 21 cm line are among the major science goals of the SKA1. Their significance lies in the fact that they are closely related to the very first stars in the…

Cosmology and Nongalactic Astrophysics · Physics 2016-11-23 T. Roy Choudhury , Kanan Datta , Suman Majumdar , Raghunath Ghara , Aseem Paranjape , Rajesh Mondal , Somnath Bharadwaj , Saumyadip Samui

Next-generation tests of fundamental physics and cosmology using large scale structure require measurements over large volumes of the Universe, including high redshifts inaccessible to present-day surveys. Line intensity mapping, an…

Cosmology and Nongalactic Astrophysics · Physics 2022-03-15 Kirit S. Karkare , Azadeh Moradinezhad Dizgah , Garrett K. Keating , Patrick Breysse , Dongwoo T. Chung

We use numerical simulations of hydrogen reionization by stellar sources in the context of LCDM cosmogonies to investigate the 21 (1+z) cm radio signal expected from the diffuse intergalactic medium (IGM) prior to the epoch of reionization…

Astrophysics · Physics 2009-07-09 B. Ciardi , P. Madau

Using high redshift radio sources as background, the 21cm forest observations probe the neutral hydrogen absorption signatures of early structures along the lines of sight. Directly sensitive to the spin temperature, it complements the 21cm…

Cosmology and Nongalactic Astrophysics · Physics 2014-11-18 Yidong Xu , Xuelei Chen , Zuhui Fan , Hy Trac , Renyue Cen