Observational Frontiers in the post-EoR 21-cm Intensity Mapping: Lessons from the SKA Pathfinders

arXiv:2606.25049 · astro-ph.CO · Submitted 2026-06-23 · Read on arXiv

Khandakar Md Asif Elahi, Somnath Bharadwaj, Philip Bull, Stefano Camera, Arnab Chakraborty, Tzu-Ching Chang, Xuelei Chen, Samir Choudhuri, Devin Crichton, Abhirup Datta, Simon Foreman, Wenkai Hu, Yichao Li, Kiyo Masui, Ainulnabilah Nasirudin, Samit Kumar Pal, Rashmi Sagar, Seth R. Siegel, Lister Staveley-Smith, Eric Switzer, Yougang Wang, Laura Wolz, Wenxiu Yang, Shifan Zuo

Indian Institute of Technology Madras, Chennai, India · Indian Institute of Technology Kharagpur, Kharagpur, India · University of Western Cape, Cape Town, South Africa · University of Western Cape, Cape Town, South Africa · McGill University, Montreal, Canada · Jet Propulsion Laboratory, California Institute of Technology, Pasadena, USA · Northeastern University, Shenyang, China · Indian Institute of Technology Madras, Chennai, India · ETH Zurich, Zurich, Switzerland · Indian Institute of Technology Indore, Indore, India · Arizona State University, Tempe, USA · National Astronomical Observatories, Chinese Academy of Sciences, Beijing, China · Northeastern University, Shenyang, China · Massachusetts Institute of Technology, Cambridge, USA · University of Manchester, Manchester, United Kingdom · Indian Institute of Technology Indore, Indore, India · Indian Institute of Technology Indore, Indore, India · Perimeter Institute for Theoretical Physics, Waterloo, Canada · University of Western Australia, Crawley, Australia · NASA Goddard Space Flight Center, Greenbelt, USA · Northeastern University, Shenyang, China · University of Manchester, Manchester, United Kingdom · University of Chinese Academy of Sciences, Beijing, China · State Key Laboratory of Radio Astronomy and Technology, Beijing, China

astro-ph.CO

Submitted: 2026-06-23

Comments: Published in Advancing Astrophysics with the SKA II (AASKAII), 2026 (arXiv:2606.20366). Report-no:AASKAII/Elahi01. Advancing Astrophysics with the SKA II (AASKAII) outlines the transformative scientific advances that will be enabled by the SKA telescopes

Code: https://github.com/TianlaiProject/fpipe

License: http://creativecommons.org/licenses/by-nc-sa/4.0/

The gist: The 21-cm line from neutral hydrogen has long been recognised as a promising tracer of the large-scale structure of the Universe.

Terminology

Abstract

The 21-cm line from neutral hydrogen has long been recognised as a promising tracer of the large-scale structure of the Universe. The line is weak however, making individual galaxy detections quite inefficient, especially at higher redshifts. The technique of 21-cm intensity mapping has been pioneered over the last two decades to address this limitation. Instead of detecting individual galaxies, the brightness temperature field from the combined 21-cm emission of many unresolved galaxies is mapped as a function of angle and frequency, resulting in 3D tracer maps of the large-scale structure. In this chapter, we review the major pioneering efforts to develop this observable into a competitive cosmological tool, paying particular attention to the status of pathfinder observations that have paved the way for a large and highly sensitive 21-cm intensity mapping survey with the SKA-Mid telescope.

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