Cosmic hydrogen measurement marks breakthrough in mapping the universe

An international research project, the MeerKLASS Collaboration, has made a groundbreaking measurement of the large-scale clustering of cosmic hydrogen, marking a significant step in mapping the universe. The study, published in the journal Monthly Notices of the Royal Astronomical Society, reports the first direct measurement of how neutral hydrogen "clumps" in the distant universe, demonstrating that its distribution follows the structure of the cosmic web. The research team used the South African MeerKAT radio telescope to analyze data across approximately 250 square degrees of sky, capturing the collective pattern of hydrogen emission from many galaxies. The observed signal originated about 4.5 billion years ago, when the universe was about 9 billion years old.

• "MeerKAT" operated each dish as an independent telescope, trading sharp angular resolution for very high survey speed, allowing the team to produce many independent maps that could be cross-compared.
• The measurement relied on a completely new observing mode for MeerKAT, enabling the detection of a signal more than six times above the statistical noise.
• The study highlights the importance of a decade of international teamwork, with researchers from seven countries and three continents contributing to the project.

This result is a milestone in establishing 21-cm intensity mapping as a novel tool for cosmology. It demonstrates that the distribution of cosmic hydrogen follows the structure of the cosmic web, providing a new way to map the universe. The measurement is a culmination of a decade of work, involving early-career scientists and highlighting the value of collaborative research. The success of the project underscores the importance of sustained and genuine teamwork in scientific endeavors, and it is a testament to the capabilities of the South African Radio Astronomy Observatory in supporting such ambitious research.

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