Atomic Hydrogen Gas Detected in Far-flung Galaxies at Record-breaking Distances

Astronomers have managed to detect the faint signal emitted by atomic hydrogen gas in galaxies that are at record-breaking distances from Earth--a staggering three billion light-years. The detects break the previous record distance by 500 million light-years, and reveal a bit more about these ancient galaxies.

In order to make the new detections, the researchers used the 305-m diameter Arecibo radio telescope in Puerto Rico. This allowed them to measure the hydrogen gas content of nearly 40 galaxies at distances of up to three billion light-years. In the end, they uncovered a unique population of galaxies hosting huge reservoirs of hydrogen gas, which is the fuel for forming new stars.

"Atomic hydrogen gas is the fuel out of which new stars are formed, hence it is a crucial component to study if we are to understand how galaxies form and evolve," said Barbara Catinella, one of the researchers, in a news release. "Because of the limitations of current instruments, astronomers still know very little about the gas content of galaxies beyond our local neighborhood."

The very gas-rich systems each contain between 20 and 80 billion times the mass of the sun in atomic gas. While these galaxies are rare today, scientists believe that they were more common in the past when the universe was younger.

This particular study actually started as an experiment to see at what distances astronomers could detect the signal from atomic hydrogen in galaxies. Needless to say, the detection methods exceeded the expectations of the astronomers.

"Not only did we detect radio signals emitted by distant galaxies when the universe was three billion years younger, but their gas reservoirs turned out to be unexpectedly large, about 10 times larger than the mass of hydrogen in our Milky Way," said Catinella. "Such a huge amount of fuel will be able to feed star formation in these galaxies for several billion years in the future."

The findings are published in the journal Monthly Notices of the Royal Astronomical Society.

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