The Milky Way is a barred spiral galaxy. The spiral arms do not rotate around a spherical core of stars, but a more elongated structure known as the bar. The evolution of bars is a very active field, and new observations from JWST are certain to add to it. The infrared telescope discovered two barred galaxies whose light comes to us from 11 billion years ago – the oldest and most distant barred spirals known.
One of the galaxies is called EGS-23205. First seen by Hubble, only the power of JWST could show that it was more than just a disk, it was a barred spiral. The second one, EGS-24268, had not been seen before. The data that delivered these insights to astronomers is part of the Cosmic Evolution Early Release Science Survey (CEERS).
"I took one look at these data, and I said, 'We are dropping everything else!'" Shardha Jogee, professor of astronomy at The University of Texas at Austin, said in a statement. "The bars hardly visible in Hubble data just popped out in the JWST image, showing the tremendous power of JWST to see the underlying structure in galaxies.”
The work found four other barred spirals closer in time to us, from 8 billion years ago. The barred structure can help with the growth of supermassive black holes residing at the center of these galaxies, and also bring in gas to form new stars.
"Bars solve the supply chain problem in galaxies," Jogee explained. "Just like we need to bring raw material from the harbor to inland factories that make new products, a bar powerfully transports gas into the central region where the gas is rapidly converted into new stars at a rate typically 10 to 100 times faster than in the rest of the galaxy."
The presence of bars so early in the history of the universe is certainly an exciting finding to understand galaxy evolution. Models can use them to better explain supermassive black hole growth and increase in star formation. At the same time, models needs to explain how many bars they have been seeing, so the presence so early in the universe might be a challenge for them as well.
"For this study, we are looking at a new regime where no one had used this kind of data or done this kind 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 nobody has ever gone into."
The research is accepted for publication in The Astrophysical Journal Letters,