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Detecting the cosmic 21-cm signal during the Epoch of Reionisation and Cosmic Dawn will reveal insights into the properties of the first galaxies and advance cosmological parameter estimation. Until recently, the primary focus for…

Cosmology and Nongalactic Astrophysics · Physics 2022-04-20 Bradley Greig , Yuan-Sen Ting , Alexander A. Kaurov

Detecting the 21-cm hyperfine transition from neutral hydrogen in the intergalactic medium is our best probe for understanding the astrophysical processes driving the Epoch of Reionisation (EoR). The primary means for a detection of this…

Cosmology and Nongalactic Astrophysics · Physics 2023-01-18 Bradley Greig , Yuan-Sen Ting , Alexander A. Kaurov

We explore the imprints of fuzzy dark matter (FDM) on the redshifted 21~cm signal from the Cosmic Dawn and the Epoch of Reionization by employing the wavelet scattering transform (WST). FDM, composed of ultralight scalar particles with…

Cosmology and Nongalactic Astrophysics · Physics 2025-12-02 Hayato Shimabukuro , Shihang Liu , Bohua Li

Optimal extraction of the non-Gaussian information encoded in the Large-Scale Structure (LSS) of the universe lies at the forefront of modern precision cosmology. We propose achieving this task through the use of the Wavelet Scattering…

Cosmology and Nongalactic Astrophysics · Physics 2022-05-30 Georgios Valogiannis , Cora Dvorkin

The absorption features in spectra of high-redshift background radio sources, caused by hyperfine structure lines of hydrogen atoms in the intervening structures, are known collectively as the 21-cm forest. They provide a unique probe of…

Cosmology and Nongalactic Astrophysics · Physics 2023-09-21 Yue Shao , Yidong Xu , Yougang Wang , Wenxiu Yang , Ran Li , Xin Zhang , Xuelei Chen

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

An alternative to both the tomography technique and the power spectrum approach is to search for the 21cm forest, that is the 21cm absorption features against high-z radio loud sources caused by the intervening cold neutral intergalactic…

Cosmology and Nongalactic Astrophysics · Physics 2015-01-20 Benedetta Ciardi , Susumu Inoue , Katherine J. Mack , Yidong Xu , Gianni Bernardi

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…

Cosmology and Nongalactic Astrophysics · Physics 2015-05-27 Katherine J. Mack , J. Stuart B. Wyithe

The interstellar medium (ISM) is a complex non-linear system governed by gravity and magneto-hydrodynamics, as well as radiative, thermodynamical, and chemical processes. Our understanding of it mostly progresses through observations and…

Cosmology and Nongalactic Astrophysics · Physics 2019-09-25 E. Allys , F. Levrier , S. Zhang , C. Colling , B. Regaldo-Saint Blancard , F. Boulanger , P. Hennebelle , S. Mallat

The 21-cm forest signal is a promising probe of the Epoch of Reionization complementary to other 21-cm line observables and Ly$\alpha$ forest signal. Prospects of detecting it have significantly improved in the last decade thanks to the…

Cosmology and Nongalactic Astrophysics · Physics 2025-01-20 Tomáš Šoltinský , Girish Kulkarni , Shriharsh P. Tendulkar , James S. Bolton

We investigate the Wavelet Scattering Transform (WST) as a tool for the study of Primordial non-Gaussianity (PNG) in Large Scale Structure (LSS), and compare its performance with that achievable via a joint analysis with power spectrum and…

Cosmology and Nongalactic Astrophysics · Physics 2024-03-27 Matteo Peron , Gabriel Jung , Michele Liguori , Massimo Pietroni

We describe a new technique for constraining the radio loud population of active galactic nuclei at high redshift by measuring the imprint of 21 cm spectral absorption features (the 21 cm forest) on the 21 cm power spectrum. Using…

Cosmology and Nongalactic Astrophysics · Physics 2014-06-03 Aaron Ewall-Wice , Joshua S. Dillon , Andrei Mesinger , Jacqueline Hewitt

We propose a new approach to improve the precision of astrophysical parameter constraints for the 21cm signal from the epoch of reionisation (EoR). Our method introduces new sets of summary statistics, hereafter `evolution compressed'…

Cosmology and Nongalactic Astrophysics · Physics 2024-06-12 Ian Hothi , Erwan Allys , Benoit Semelin , Francois Boulanger

We make forecasts for the constraining power of the 1D Wavelet Scattering Transform (WST) when used with a Lyman-$\alpha$ forest cosmology survey. Using mock simulations and a Fisher matrix, we show that there is considerable cosmological…

Cosmology and Nongalactic Astrophysics · Physics 2026-02-05 Hurum Maksora Tohfa , Simeon Bird , Ming-Feng Ho , Mahdi Qezlou , Martin Fernandez

The statistical characterization of the diffuse magnetized ISM and Galactic foregrounds to the CMB poses a major challenge. To account for their non-Gaussian statistics, we need a data analysis approach capable of efficiently quantifying…

Cosmology and Nongalactic Astrophysics · Physics 2020-10-28 Bruno Regaldo-Saint Blancard , François Levrier , Erwan Allys , Elena Bellomi , François Boulanger

The 21-cm forest, comprising narrow absorption features imprinted on the radio spectra of high-redshift radio-loud quasars by intervening neutral hydrogen, offers a uniquely sensitive probe of the thermal state of the neutral intergalactic…

Cosmology and Nongalactic Astrophysics · Physics 2026-02-25 Sameer K. Patil , Tomáš Šoltinský , Soumak Maitra , Girish Kulkarni

The information regarding how the intergalactic medium is reionized by astrophysical sources is contained in the tomographic three-dimensional 21 cm images from the epoch of reionization. In Zhao et al. (2022a) ("Paper I"), we demonstrated…

Instrumentation and Methods for Astrophysics · Physics 2024-09-12 Xiaosheng Zhao , Yi Mao , Shifan Zuo , Benjamin D. Wandelt

Understanding the nature of dark matter (DM) particles remains a pivotal challenge in modern cosmology. Current cosmological research on these phenomena primarily utilizes cosmic microwave background (CMB) observations and other late-time…

Cosmology and Nongalactic Astrophysics · Physics 2026-02-24 Meng-Lin Zhao , Yue Shao , Sai Wang , Xin Zhang

We discuss the feasibility of the detection of the 21cm forest in the diffuse IGM with the radio telescope LOFAR. The optical depth to the 21cm line has been derived using simulations of reionization which include detailed radiative…

Large-scale structure (LSS) analysis in galaxy surveys is a powerful cosmological probe but is limited by tracer bias, which can obscure underlying information and weaken parameter constraints. Existing methods either model bias or restrict…

Cosmology and Nongalactic Astrophysics · Physics 2025-12-01 Zhujun Jiang , Xiaolin Luo , Wenying Du , Zhiwei Min , Fenfen Yin , Longlong Feng , Jiacheng Ding , Le Zhang , Xiao-Dong Li
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