South Africa’s MeerKAT radio telescope array has chalked up yet another astronomical first. A team of South African and international astronomers has used MeerKAT to, for the first time, measure the neutral hydrogen gas (which is the material that forms and fuels stars) around galaxies as they were four-billion years ago. (Or, in other words, galaxies that lie four billion light years from Earth.) Neutral hydrogen gas is the most abundant material in the universe.

“For the first time, the team were able to measure the hydrogen gas for galaxies of different sizes and star formation activity to determine how the fuel content relates to other observable properties of galaxies four-billion years in the past,” highlighted University of Cape Town eResearch rirector Professor Mattia Vaccari. “These were compared to galaxies in the present day.”

And the results of the comparison surprised the astronomers. They had expected that galaxies four-billion years ago would have more neutral hydrogen gas in and around them than younger, closer galaxies would have. This was because it was thought that a lot of the neutral hydrogen gas would be consumed by the processes of star formation. What they discovered was that these older, more remote galaxies had similar amounts of the gas to younger, closer galaxies. This, in turn, signals that galaxies can and do replenish their ‘reservoirs’ of neutral hydrogen gas.

“We were thrilled to exploit the potential of MeerKAT to improve our understanding of the cold gas in distant galaxies,” said study lead author and University of Padova (Italy) PhD candidate Francesco Sinigaglia. “We believe this study represents a strong step forward in the field, as it delivers new pieces of information on hydrogen in galaxies, never obtained before.”

This research was only possible because of the existence of MeerKAT and used radio wavelength data from the MeerKAT International GigaHertz Tiered Extragalactic Exploration (MIGHTEE) project (an international large astronomical survey), supplemented by data from optical telescopes. The data was processed by South Africa’s Inter-University Institute for Data Intensive Astronomy (IDIA).

“The data taught us a lot about the processing challenges involved and was an important testbed for coordinating science projects,” affirmed IDIA associate director for astronomy computing and MIGHTEE-Neutral Hydrogen co-chair Dr Bradley Frank. “Francesco’s science result is the perfect validation for our processing strategy and teamwork, providing an exciting glimpse of the future of MIGHTEE.”

Other members of the research team included Sinigaglia’s PhD supervisor, University of Padova Associate Professor Giulia Rodighiero, and University of Western Cape astronomer Dr Ed Elson. “This is wonderful fundamental science, made possible by South Africa building the most powerful telescope of its kind in the world, thereby attracting international collaboration with South Africans at the very top level,” emphasised South African Radio Astronomy Observatory MD Dr Rob Adam.