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During the epoch of reionization (EoR), the 21-cm signal allows direct observation of the neutral hydrogen (HI) in the intergalactic medium (IGM). In the post-reionization era, this signal instead probes HI in galaxies, which traces the…

Cosmology and Nongalactic Astrophysics · Physics 2024-08-20 Sambit K. Giri , Michele Bianco , Timothée Schaeffer , Ilian T. Iliev , Garrelt Mellema , Aurel Schneider

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

In this paper, we propose a novel method to recover the 21cm global signal from the 21cm power spectrum using artificial neural networks (ANNs). The 21cm global signal is crucial for understanding cosmic evolution from the Dark Ages through…

Cosmology and Nongalactic Astrophysics · Physics 2025-07-09 Hayato Shimabukuro

Gaussian process regression is a widespread tool used to mitigate stellar correlated noise in radial velocity time series. It is particularly useful to search for and determine the properties of signals induced by small-size, low-mass…

Earth and Planetary Astrophysics · Physics 2019-08-21 M. Damasso , M. Pinamonti , G. Scandariato , A. Sozzetti

We demonstrate the effectiveness of a Bayesian evidence-based analysis for diagnosing and disentangling the sky-averaged 21-cm signal from instrumental systematic effects. As a case study, we consider a simulated REACH pipeline with an…

Cosmology and Nongalactic Astrophysics · Physics 2022-10-26 K. H. Scheutwinkel , E. de Lera Acedo , W. Handley

The 21 cm line of neutral hydrogen is a promising probe of the Epoch of Reionization (EoR) but suffers from contamination by spectrally smooth foregrounds, which obscure the large-scale signal along the line of sight. We explore the…

Cosmology and Nongalactic Astrophysics · Physics 2026-02-26 Wenzer Qin , Kai-Feng Chen , Katelin Schutz , Adrian Liu

Satellite-based positioning system such as GPS often suffers from large amount of noise that degrades the positioning accuracy dramatically especially in real-time applications. In this work, we consider a data-mining approach to enhance…

Machine Learning · Statistics 2019-06-05 Ming Lin , Xiaomin Song , Qi Qian , Hao Li , Liang Sun , Shenghuo Zhu , Rong Jin

We show that Gaussian process regression (GPR) can be used to infer the electromagnetic (EM) duct height within the marine atmospheric boundary layer (MABL) from sparsely sampled propagation factors within the context of bistatic radars. We…

Atmospheric and Oceanic Physics · Physics 2020-07-15 Hilarie Sit , Christopher J. Earls

Due to the large dynamic ranges involved with separating the cosmological 21-cm signal from the Cosmic Dawn from galactic foregrounds, a well-calibrated instrument is essential to avoid biases from instrumental systematics. In this paper we…

The data analysis problem of coherently searching for unmodeled gravitational-wave bursts in the data generated by a global network of gravitational-wave observatories has been at the center of research for almost two decades. As data from…

General Relativity and Quantum Cosmology · Physics 2010-04-21 Antony C. Searle , Patrick J. Sutton , Massimo Tinto

We introduce the Bayesian Global Sky Model (B-GSM), a novel data-driven Bayesian approach to modelling radio foregrounds at frequencies <400~MHz. B-GSM aims to address the limitations of previous models by incorporating robust error…

Instrumentation and Methods for Astrophysics · Physics 2025-11-12 George Carter , Will Handley , Mark Ashdown , Nima Razavi-Ghods

Radio interferometers, such as the Low-Frequency Array and the future Square Kilometre Array, are attempting to measure the spherically averaged 21-cm power spectrum from the Epoch of Reionization. Understanding of the dominant physical…

Cosmology and Nongalactic Astrophysics · Physics 2022-06-01 Ivelin Georgiev , Garrelt Mellema , Sambit K. Giri , Rajesh Mondal

We report the deepest upper limits to date on the power spectrum of the 21-cm signal during the Cosmic Dawn (redshifts: $z>15$), using four nights of observations with NenuFAR. The limits are derived from two redshift bins, centred at…

In this article, we consider the general task of performing Gaussian process regression (GPR) on pointwise observations of solutions of the 3 dimensional homogeneous free space wave equation.In a recent article, we obtained promising…

Analysis of PDEs · Mathematics 2023-11-10 Iain Henderson , Pascal Noble , Olivier Roustant

We are approaching a new era to probe the 21-cm neutral hydrogen signal from the period of cosmic dawn. This signal offers a unique window to the virgin Universe, e.g., to study dark matter models with different small-scale behaviours. The…

Cosmology and Nongalactic Astrophysics · Physics 2021-06-21 Venno Vipp , Andi Hektor , Gert Hütsi

Radio-interferometric arrays require very precise calibration to detect the Epoch of Reionization 21-cm signal. A remarkably complete and accurate sky model is therefore needed in the patches of the sky used to perform the calibration.…

Cosmology and Nongalactic Astrophysics · Physics 2025-10-13 Khandakar Md Asif Elahi , Samir Choudhuri , Nirupam Roy , Md Rashid , Philip Bull , Dharam Vir Lal

Detection of redshifted \ion{H}{i} 21-cm emission is a potential probe for investigating the Universe's first billion years. However, given the significantly brighter foreground, detecting 21-cm is observationally difficult. The Earth's…

Cosmology and Nongalactic Astrophysics · Physics 2024-01-30 Anshuman Tripathi , Abhirup Datta , Madhurima Choudhury , Suman Majumdar

The redshifted 21 cm absorption trough from cosmic atomic hydrogen is one of the most promising probes of the early Universe, but its detection is challenged by bright foregrounds and instrumental systematics. In this work we quantify the…

Cosmology and Nongalactic Astrophysics · Physics 2026-03-27 Joe H. N. Pattison , John M. Cumner , Dominic J. Anstey , Saurabh Pegwal , Wessel Croukamp , Dirk I. L. de Villiers , Eloy de Lera Acedo

The redshifted 21cm signal from the post-reionization epoch is highly non-Gaussian; thus, higher-order statistics, such as the bispectrum, are required to extract this non-Gaussian information. However, high-signal-to-noise ratio detection…

The observations of the redshifted 21-cm signal from neutral hydrogen are a promising probe for understanding the Cosmic Dawn and the Epoch of Reionisation (EoR). One of the primary obstacles to the statistical detection of the Cosmological…

Cosmology and Nongalactic Astrophysics · Physics 2026-05-22 Eeshan Beohar , Abhirup Datta , Anshuman Tripathi , Samit Kumar Pal , Rashmi Sagar