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The cosmic microwave background absorption intensity in the 21 cm line of neutral hydrogen in the presence of additional power in the form of a "bump" in the spectrum of cosmological density perturbations is calculated. The main…

Cosmology and Nongalactic Astrophysics · Physics 2025-12-09 Yu. N. Eroshenko , V. N. Lukash , E. V. Mikheeva , S. V. Pilipenko , M. V. Tkachev

Line intensity mapping using atomic hydrogen (HI) has the potential to efficiently map large volumes of the universe if the signal can be successfully separated from overwhelmingly bright radio foreground emission. This motivates…

A new generation of interferometric instruments is emerging which aim to use intensity mapping of redshifted $21\,$cm radiation to measure the large-scale structure of the Universe at $z\simeq 1-2$ over wide areas of sky. While these…

Cosmology and Nongalactic Astrophysics · Physics 2017-08-16 Martin White , Nikhil Padmanabhan

Numerous studies have established the theoretical potential of the 21cm bispectrum to boost our understanding of the Epoch of Reionization (EoR), and therefore early generation of stars and galaxies. In this paper we look at the impact of…

Cosmology and Nongalactic Astrophysics · Physics 2020-12-09 Catherine A Watkinson , Cathryn M Trott , Ian Hothi

The low-frequency radio sky is dominated by the diffuse synchrotron emission of our Galaxy and extragalactic radio sources related to Active Galactic Nuclei and star-forming galaxies. This foreground emission is much brighter than the…

Cosmology and Nongalactic Astrophysics · Physics 2019-09-30 Emma Chapman , Vibor Jelić

In order to extract cosmological information from observations of the millimeter and submillimeter sky, foreground components must first be removed to produce an estimate of the cosmic microwave background (CMB). We developed a…

Cosmology and Nongalactic Astrophysics · Physics 2020-11-10 Matthew A. Petroff , Graeme E. Addison , Charles L. Bennett , Janet L. Weiland

Predictions for the ability of 21-cm interferometric experiments to discriminate Epoch of Reionization (EoR) signal models are typically limited by the simplicity of data models, whereby foreground signals and characteristics of the…

Cosmology and Nongalactic Astrophysics · Physics 2020-04-29 Ainulnabilah Nasirudin , Steven Murray , Cathryn Trott , Bradley Greig , Ronniy Joseph , Chris Power

Apart from its anomalously large depth, the cosmological 21-cm absorption signal measured by the EDGES collaboration also has a shape that is distinctly different from theoretical predictions. Models with non-traditional components such as…

Cosmology and Nongalactic Astrophysics · Physics 2022-08-03 Shikhar Mittal , Girish Kulkarni

Numerous experiments have been designed to investigate the Cosmic Dawn (CD) and Epoch of Reionization (EoR) by examining redshifted 21-cm emissions from neutral hydrogen. Detecting the global spectrum of redshifted 21-cm signals is…

Instrumentation and Methods for Astrophysics · Physics 2025-04-08 Feiyu Zhao , Quan Guo , Qian Zheng , Ruxi Liang , Pengfei Zhang , Yajun Wu , Junhua Gu , Zhao Yang , Yun Yu , Yan Huang , Tianyang Liu

21 cm tomography is expected to be difficult in part because of serious foreground contamination. Previous studies have found that line-of-sight approaches are capable of cleaning foregrounds to an acceptable level on large spatial scales,…

Cosmology and Nongalactic Astrophysics · Physics 2009-09-05 Adrian Liu , Max Tegmark , Judd Bowman , Jacqueline Hewitt , Matias Zaldarriaga

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

The Cosmological Principle states that the universe is statistically isotropic and homogeneous on large length scales, typically $\gtrsim 70$Mpc. A detection of significant deviation would help us falsify the simplest models of inflation.…

Cosmology and Nongalactic Astrophysics · Physics 2025-08-26 Bhuwan Joshi , Rahul Kothari

Foreground removal presents a significant obstacle in both current and forthcoming intensity mapping surveys. While numerous techniques have been developed that show promise in simulated datasets, their efficacy often diminishes when…

Cosmology and Nongalactic Astrophysics · Physics 2024-08-14 Jiacheng Ding , Xin Wang , Ue-Li Pen , Xiao-Dong Li

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

The upcoming Square Kilometre Array Observatory (SKAO) will produce images of neutral hydrogen distribution during the epoch of reionization by observing the corresponding 21-cm signal. However, the 21-cm signal will be subject to…

Instrumentation and Methods for Astrophysics · Physics 2024-02-29 Michele Bianco , Sambit. K. Giri , David Prelogović , Tianyue Chen , Florent G. Mertens , Emma Tolley , Andrei Mesinger , Jean-Paul Kneib

Future high-sensitivity measurements of the cosmic microwave background (CMB) anisotropies and energy spectrum will be limited by our understanding and modeling of foregrounds. Not only does more information need to be gathered and…

Cosmology and Nongalactic Astrophysics · Physics 2017-09-20 Jens Chluba , J. Colin Hill , Maximilian H. Abitbol

Absorption lines at $\lambda$ 21-cm are detected in the Stokes Q and U components of the Galactic synchrotron background. The lower limit distance implied for the emission region is 2 kpc in the direction (l,b) =…

Astrophysics · Physics 2009-10-30 John M. Dickey

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

A detection of the predicted anticorrelation between 21cm and either Ly-alpha or H-alpha from the Epoch of Reionization (EOR) would be a powerful probe of the first galaxies. While 3D intensity maps isolate foregrounds in low k_\parallel…

Cosmology and Nongalactic Astrophysics · Physics 2017-11-06 Abraham R. Neben , Brian Stalder , Jacqueline N. Hewitt , John L. Tonry

The sky-averaged (global) highly redshifted 21-cm spectrum from neutral hydrogen is expected to appear in the VHF range of $\sim20-200$ MHz and its spectral shape and strength are determined by the heating properties of the first stars and…

Instrumentation and Methods for Astrophysics · Physics 2018-10-24 Keith Tauscher , David Rapetti , Jack O. Burns , Eric R. Switzer