Astronomers have detected a massive reservoir of cold molecular gas in a massive early galaxy for the first time. This provides direct evidence that some galaxies already possessed enormous reserves of fuel for star formation when the universe was only 700 million years old.
Fuel for the stars
Researchers at Leiden University focused on the galaxy REBELS-25, which we see as it was during the first 5% of the universe’s existence. Scientists have long suspected that the bright, massive galaxies of that era had enormous gas reserves, but they had never directly detected them at such distances.
The team used two instruments for the observations. The National Science Foundation’s (NSF) Very Large Array (VLA) in New Mexico detected faint radio emissions from carbon monoxide molecules, while the Atacama Large Millimeter/submillimeter Array (ALMA) in the Chilean Andes provided data on higher-energy states of the same gas. Together, they made it possible to estimate its density and temperature under conditions in the early universe.
The faintest signal
The detected carbon monoxide line represents the most distant detection of a low-energy signal of this type in the history of astronomy. The signal was bright enough to indicate a truly large supply of star-forming material.
The observations were complicated by the cosmic microwave background. At high redshifts, it becomes significantly brighter and weakens the contrast of cold gas in early galaxies. Leiden University PhD student and lead author of the study Karin Cescon noted that it was the deep observations from the NSF VLA that made it possible to overcome this obstacle.
Why did galaxies grow so quickly?
This new discovery answers a question that has long puzzled cosmologists. Previously, scientists could only estimate the gas reserves in early galaxies indirectly, either through the rate of star formation or through luminosity. Now, for the first time, they have managed to measure the actual fuel that drove this process.
The large gas supply in REBELS-25 suggests that some early galaxies had all the conditions necessary for intense star formation right from the start. This is a key piece of the puzzle in understanding how such massive structures formed during the first billion years of the universe’s existence.
The next generation of telescopes
The prototype of the Next-Generation Very Large Array (ngVLA) has already collected its first light and undergone initial testing. Once it is fully operational, such measurements will be performed ten times faster and will cover a much larger number of early galaxies.
Jacqueline Hodge, a professor at Leiden University, noted that the future ngVLA would allow researchers to study cold gas in young galaxies that existed even earlier than REBELS-25. The study was published in the journal Monthly Notices of the Royal Astronomical Society.
According to phys.org
