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The galaxies that formed in the first billions of years after the Big Bang should have lived long and healthy lives. After all, they were born with rich reserves of cold hydrogen gas, exactly the fuel needed to continue star formation.
But new observations have revealed “extinct” galaxies that interrupted star formation. And astronomers don’t know why.
An international team of astronomers studied a cluster of six primitive galaxies with the Atacama Large Millimeter / submillimeter Array (ALMA) and the Hubble Space Telescope. The research results were recently published in Nature.
These galaxies were targeted because they were known to be “extinct”, with little or no star formation.
Previously, astronomers believed something had happened to stop star formation in these otherwise rich galaxies.
“The most massive galaxies in the Universe lived fast and furiously, creating their stars in a remarkably short span of time. Gas, the fuel for star formation, should be plentiful in these early days of the Universe.” said Kate Whitaker, lead author on the study, and assistant professor of astronomy at the University of Massachusetts, Amherst.
“We originally thought that these extinct galaxies had braked just a few billion years after the Big Bang. In our new research, we concluded that the first galaxies did not brake, but rather that they were running on empty. . ”
Usually these types of galaxies are so far apart that they are impossible to solve, but the team behind the investigation (called REQUIEM, for REsolving QUIEscent Magnified galaxies) used a trick: they used gravitational lenses. around nearby galaxies to amplify images of the target galaxies.
“If a galaxy doesn’t make a lot of new stars, it gets very faint very quickly, so it’s difficult or impossible to observe them in detail with an individual telescope. REQUIEM solves this problem by studying gravitational lens galaxies, which means that their light stretches and magnifies as it bends and warps around other galaxies much closer to the Milky Way, ”said Justin Spilker, co-author of the new study and NASA Hubble postdoctoral fellow at the University of Texas at Austin.
“In this way, the gravitational lens, combined with the resolving power and sensitivity of Hubble and ALMA, acts like a natural telescope and makes these dying galaxies appear larger and brighter than they actually are,” allowing us to see what is happening and what is happening. ‘t. “
The team found that, contrary to expectations, there had been no sudden drop in the ability of galaxies to turn cold gas into stars. On the contrary, the stars were completely lacking in cold gas.
“We don’t yet understand why this is happening, but the possible explanations could be that the main gas supply to the galaxy is cut off, or maybe a supermassive black hole is injecting energy that keeps the gas hot. in the galaxy, ”Christina said. Williams, University of Arizona astronomer and research co-author.
“Essentially, this means that the galaxies are unable to fill the fuel tank, and therefore unable to restart the engine when producing stars.”
But what is it that removes cold gas from galaxies? Astronomers are perplexed and will have to continue their observations to find clues to this great galactic mystery.
“We still have so much to learn about the reasons why the most massive galaxies formed so early in the Universe and why they stopped their star formation when they had so much cold gas,” said Whitaker said.
“The simple fact that these huge beasts of the cosmos formed 100 billion stars in about a billion years and then suddenly stopped star formation is a mystery we would all like to solve, and REQUIEM provided the first clue. “
This article was originally published by Universe Today. Read the original article.
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