CAPE TOWN, Sept. 4 (Xinhua) -- An international team of astronomers has used South Africa's MeerKAT radio telescope to directly detect faint radio emission from neutral hydrogen gas across cosmic distances, providing a new way to trace the large-scale structure of the universe.
The finding, published in The Astrophysical Journal Letters, involved astronomers from the University of the Western Cape (UWC) in South Africa and the University of Manchester in Britain, UWC spokesperson Gasant Abader told Xinhua on Friday.
The new study detected the signal using MeerKAT radio observations alone, despite the data not originally being collected for the experiment. The finding marks a significant step toward using neutral hydrogen to map the three-dimensional structure of the universe on large scales, according to a UWC statement.
The team analyzed about 96 hours of MeerKAT observations and detected the signal from two periods in cosmic history, corresponding to redshifts of about 0.32 and 0.44. The emission traveled roughly four to five billion years before reaching Earth, tracing hydrogen over megaparsec scales.
"The signal is extremely faint and difficult to isolate from foreground emission, human-made radio-frequency interference, and instrumental effects," Sourabh Paul, lead author of the study, was quoted as saying in the statement. "Detecting it directly with MeerKAT shows that this technique is becoming a practical tool for cosmology."
The MeerKAT telescope, operated by the South African Radio Astronomy Observatory in the country's remote Karoo region, consists of 64 radio dishes. It is a precursor to the Square Kilometer Array Observatory, which is expected to begin science operations around 2028.
"MeerKAT continues to open new windows for cosmology," said Laura Wolz, a co-author from the University of Manchester.
"The fact that this signal can be extracted from observations that were not originally designed for hydrogen intensity mapping is very encouraging," she said.
Neutral hydrogen emits a faint radio signal known as the 21-cm line. As the universe expands, the signal is stretched to longer wavelengths, allowing astronomers to trace hydrogen at different stages of cosmic history.
Hydrogen intensity mapping measures the combined emission from many unresolved galaxies rather than detecting individual galaxies, enabling surveys of vast regions of the universe.
Previous robust detections of the signal at similar redshifts have typically combined radio observations with optical galaxy surveys. ■
