Stellar bars are elongated features of stars extending from the centers of galaxies to their outer disks.
The discovery of so-called barred galaxies similar to our Milky Way in this early phase of the universe will require astrophysicists to refine their theories of galaxy evolution.
Before the James Webb Space Telescope (JWST), images from the Hubble Space Telescope had never detected bands at such young epochs. In a Hubble image, one galaxy, EGS-23205, is little more than a disc-shaped blob, but in the corresponding JWST image taken last summer, it’s a beautiful spiral galaxy with a clear star bar.
JWST’s power to map galaxies at high resolution and at longer infrared wavelengths than Hubble allows it to peer through dust and reveal the underlying structure and mass of distant galaxies. This can be seen in these two images of the galaxy EGS23205, seen as it was about 11 billion years ago. In the HST image (left, taken in the near-infrared filter), the galaxy is little more than a disc-like blob obscured by dust and affected by the glow of young stars, but in the corresponding JWST mid-infrared image (taken last summer), it’s a beautiful spiral galaxy with clear star band. (Credit: NASA/CEERS/UT Austin)
“I looked at this data and said, ‘We’re throwing everything else away!'” says Sharda Jogi, a professor of astronomy at the University of Texas at Austin.
“Bands that were barely visible in the Hubble data just popped up in the JWST image, showing the tremendous power of JWST to see the underlying structure in galaxies,” she says, describing data from the Cosmic Evolutionary Early Release Survey (CEERS ), led by UT Austin Professor Steven Finkelstein.
The team identified another barred galaxy, EGS-24268, also from about 11 billion years ago, making two barred galaxies more ancient than any discovered so far.
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 at a new regime where no one has used this kind of data or done this kind of quantitative analysis before,” says Yuchen “Kei” Guo, the graduate student who led the analysis, “so everything is new. It’s like going into a forest where no one has ever been before.”
Lattices play an important role in the evolution of galaxies by directing gas into the central regions, stimulating star formation.
“Bars solve the galactic supply chain problem,” says Jogi. “Just as we need to bring raw material from the harbor to the inland factories that make new products, the bar powerfully transports gas into the central region, where the gas rapidly turns into new stars at a rate typically 10 to 100 times faster than in the rest from the galaxy.”
Bars also help the growth of supermassive black holes at the centers of galaxies by channeling the gas part of the way.
The discovery of bars at such early epochs 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,” says Jogi.
And the very existence of these early bars challenges theoretical models because they need to get the physics of the galaxy right to predict the right abundance of bars. The team will test different models in their next papers.
JWST can reveal structures in distant galaxies better than Hubble for two reasons: First, its larger mirror gives it more light-gathering ability, allowing it to see farther and with higher resolution. Second, it can see better through dust because it observes at longer infrared wavelengths than Hubble.
Students Eden Wise and Zilei Chen played a key role in the study by visually inspecting hundreds of galaxies, looking for those that appeared to have bars, which helped narrow the list down to a few dozen for other researchers to analyze with a more intensive mathematical approach.
Additional co-authors are from UT Austin and other institutions in the US, UK, Japan, Spain, France, Italy, Australia and Israel.
Funding for this research came in part from the Roland K. Bloomberg Astronomy Foundation, the Heising-Simons Foundation, and NASA. This work relied on resources at the Texas Advanced Computing Center.
This article was originally published on Futurity. Republished under an Attribution 4.0 International license.
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