New images from the James Webb Space Telescope (JWST) reveal for the first time galaxies with stellar bars.
(elongated features of stars extending from the center of galaxies toward their outer disks) at a time when the universe was only 25% full. his present age.
Finding so-called barred galaxies, similar to our Milky Way , so early in the universe will require astrophysicists to refine their theories of galaxy evolution.
Challenging spatial paradigms
Before James Webb , Hubble Space Telescope images had never detected bars at such young times. In one Hubble image, one galaxy, EGS-23205 , is little more than a disk-shaped blob, but in the corresponding JWST image taken last summer, it’s a beautiful spiral galaxy with a clear star bar. Both are shown above.
“I took one look at this data and said, ‘Let’s drop everything else!'” said Shardha Jogee, a professor of astronomy at the University of Texas at Austin. “The faint bars in the Hubble data just showed up in the James Webb image , showing the tremendous power of the JWST to see the underlying structure in galaxies,” he said in a statement, describing the data from the Cosmic Evolution Early Release Science Survey. (CEERS), led by UT Austin professor Steven Finkelstein.
The team identified another barred galaxy, EGS-24268 , also from around 11 billion years ago, making two barred galaxies exist further back in time than any previously discovered.
In a paper accepted for publication in The Astrophysical Journal Letters , they highlight these two galaxies and show examples of four other barred galaxies from more than 8 billion years ago.
“For this study, we are looking for a new regimen where no one has used this type of data or done this type of quantitative analysis before,” said Yuchen “Kay” Guo, a graduate student who led the analysis. “So everything is new. It’s like going into a forest that no one has ever been in before.”
The bars play an important role in the evolution of galaxies by funneling gas into the central regions, which drives star formation.
“The bars solve the supply chain problem in galaxies,” Jogee said. “Just like we need to get raw materials from the port to inland factories that make new products, a rod transports gas with force to the Midwest, where the gas rapidly turns into new stars at a rate typically 10 to 100 times faster than in the rest of the galaxy.” The bars also help supermassive black holes grow at the centers of galaxies by funneling gas part of the way.
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The discovery of bars during such early times shakes up galaxy evolution scenarios in several ways. “This discovery of early bars means that models of galaxy evolution now have a new path through bars to accelerate the production of new stars at early epochs,” Jogee said.
And the very existence of these early bars defies theoretical models, since they need to get the physics of the galaxy right to predict the correct abundance of bars. The team will test different models in their next articles.
James Webb can reveal structures in distant galaxies better than Hubble for two reasons: First, its larger mirror gives it greater light-gathering ability, allowing it to see farther and with higher resolution. Second, it can see through the dust better, since it observes at longer infrared wavelengths than Hubble.
Undergraduate students Eden Wise and Zilei Chen played a key role in the research by visually reviewing hundreds of galaxies, looking for those that appeared to have bars, helping to narrow the list down to a few dozen for other researchers to analyze with a more intensive mathematical approach. (Europe Press)