Scientists studying the first galaxies were stunned earlier this year when they discovered six massive galaxies that appear to have died during the most active birth period of the stars in the universe. NASA’s Hubble Space Telescope spied on the six galaxies, which appeared to have run out of the cold hydrogen gas needed to make stars while most other galaxies produced new stars at a fast pace.
“At this time in our universe, all galaxies should form many stars. It’s the peak time of star formation,” said Kate Whitaker, assistant professor of astronomy at the University of Massachusetts, Amherst, lead author. from a recent study of the six galaxies, it said in a press release. “So what happened to all the cold gas in these galaxies so soon?”
Without the cold hydrogen gas needed to power stars and the birth of new ones, galaxies are essentially dead. Nor can they rejuvenate, even if they have absorbed smaller galaxies and nearby gas clouds. Whitaker said the act of absorbing only “inflated” dead galaxies.
But the reason they died in the first place is still a mystery.
“Did a supermassive black hole ignite in the center of the galaxy and heat up all the gas?” Whitaker raised. “If so, the gas could still be there, but it’s hot now. Or could it have been ejected and now prevented from returning to the galaxy. Or has the galaxy only used it even though the supply is cut off?”
“These are some of the open questions we will continue to explore with new observations along the way,” Whitaker added.
Astronomers used Hubble to identify galaxies, and then using the Atacama Large Millimeter / Submillimeter (ALMA) matrix in northern Chile, researchers were able to detect whether or not the galaxies contained the cold dust that indicates their existence. of cold hydrogen gas.
But because galaxies were so ancient and so far away, scientists would not have been able to detect them without a technique known as the “gravitational lens,” NASA said. The team used supermassive clusters of galaxies that were closer to Earth as natural telescopes. The light of the background objects is amplified by the gravity of these groups. According to NASA, when very distant galaxies are behind clusters, they appear stretched and magnified in the images, which helps astronomers see details that would otherwise be lost without the increase in galaxy clusters.
“By using strong gravitational lenses as a natural telescope, we can find the first more distant, massive galaxies that closed their star formation,” Whitaker said. “I like to think about how to do science in the 2030s or ’40s (with powerful next-generation space telescopes), but today combining the capabilities of Hubble and ALMA, which are bolstered by a sharp slowdown.”
Mohammad Akhshik, lead researcher on Hubble’s observation program, said the team gathered the largest sample to date of these rare dead galaxies in the early universe.