Astronomers Hear the Faint Whispers of Cosmic Hydrogen from the Distant Past.

Astronomers from the University of Manchester and the University of the Western Cape detected a faint radio signal from neutral hydrogen, which existed when the universe was about 10 and 9 billion years old. The signal was observed using the MeerKAT telescope in South Africa, and it was the first time a single observatory directly detected cosmic hydrogen. The study, published in The Astrophysical Journal Letters, used 96 hours of MeerKAT data to detect two signals at redshifts z = 0.32 and 0.44, corresponding to distances of 3.67 and 4.76 billion light-years. The technique, called Hydrogen Intensity Mapping (HIM), allows astronomers to study the universe's history by measuring the combined radio emission of many galaxies.

The team analyzed data from MeerKAT and found the signal was extremely faint, making it difficult to isolate from foreground emission and instrumental effects. The signal was detected nearly a decade ago, when MeerKAT was just starting science operations. This discovery highlights the potential of HIM as a practical tool for cosmology, as it allows for efficient mapping of the universe without needing to detect individual galaxies. The study also shows that MeerKAT data can be used to extend cosmological surveys, providing new insights into galaxy formation and the role of dark matter and dark energy.

The research emphasizes the importance of MeerKAT in opening new windows for cosmology. The signal was extracted from data not originally designed for hydrogen intensity mapping, demonstrating the scientific value of the observatory's archival data. The study's results suggest there could be many more signals in MeerKAT's data that could be used for future cosmological surveys. Co-authors highlighted the significance of the findings in understanding how galaxies form and evolve, and how dark matter and dark energy shape the cosmic web. The work also points the way to future observations with the Square Kilometer Array Observatory (SKAO), which will combine data from MeerKAT and the MRAO in Australia.

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