Webb Space Telescope rewrites the rules of galactic evolution

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Formation of galaxies Art

Discoveries with the James Webb Space Telescope suggest that early galaxies formed complex structures such as bars much earlier, indicating accelerated evolution. Credit: SciTechDaily

Advanced observations from the JWST indicate that early galaxies matured more quickly and were less chaotic, challenging previous theories of galaxy evolution.

New research has found that the universe’s early galaxies were less turbulent and developed more quickly than previously thought. This research, led by an international team from the University of Durham, used the James Webb Space Telescope (JWST) to find evidence of bar formation when the universe was just a few billion years old.

These findings were published in the journal Monthly notices of the Royal Astronomical Society.

Milky Way Galaxy Illustration

Artist’s impression of the structure of the Milky Way. The bar is the yellowish elongated structure that crosses the center of the Milky Way. Credit: NASA/JPL-Caltech/R. Pain (SSC/Caltech)

Insights from the James Webb Space Telescope

Bars are elongated strips of stars that occur in disk or spiral galaxies like ours Milky Way. As the bars develop, they regulate star formation in a galaxy, pushing gas toward the central region of the galaxy. Their presence tells scientists that galaxies have entered a steady, mature phase.

Previous studies using the Hubble Space Telescope identified galaxies that formed bars eight to nine billion years ago. However, the improved sensitivity and wider wavelength range of the JWST have allowed astronomers to detect these phenomena even further back in time.

Hubble Webb space telescope Galaxy EGS 31125

A grayscale image of the galaxy EGS_31125 from 10.6 billion years ago, visually classified as heavily streaked (outlined in the center image by a thick, solid purple line, with the spiral arms shown as faint purple lines). From left to right: Hubble Space Telescope WFC3 F160W and James Webb Space Telescope NIRCam F356W and F444W. This filter comparison demonstrates the effects of Point Spread Function (PSF), sensitivity and wavelength range on a galaxy image, especially in the context of bars. Credit: Zoe Le Conte

“Galaxies in the early universe matured much faster than we thought. This is a real surprise, because you would expect the universe to be very turbulent at that stage, with many collisions between galaxies and a lot of gas that has not yet transformed into stars,” explains author Zoe Le Conte, a PhD candidate at the University of California. Center for Extragalactic Astronomy, Department of Physics, University of Durham.

“But thanks to the James Webb Space Telescope We see many of these bars much earlier in the life of the universe, meaning that galaxies were at a calmer stage in their evolution than previously thought,” she adds. The researchers say this new evidence suggests that theories about the early evolution of galaxies may need significant revisions.

Hubble Space Telescope image of the Milky Way Galaxy EGS_31125

A grayscale image of the galaxy EGS_31125 from 10.6 billion years ago, as seen by the Hubble Space Telescope. The bar of the galaxy cannot be seen. Credit: Zoe Le Conte

Research methodology and findings

The researchers used the JWST to look for bar formation in galaxies as they would have been observed between 8 and 11.5 billion years ago. The universe itself is 13.7 billion years old. Of the 368 observed disk galaxies, the researchers saw that almost 20 percent had bars – twice as many as observed by Hubble.

Co-author Dr. Dimitri Gadotti, from the Center for Extragalactic Astronomy, Department of Physics, Durham University, said: “We find that there were many more bars present in the early universe than previously found in Hubble studies, implying that bar-driven galaxies Evolution has been happening for much longer than previously thought.”

James Webb Space Telescope image of Milky Way Galaxy EGS_31125

A grayscale image of the galaxy EGS_31125, 10.6 billion years ago, as seen by the James Webb Space Telescope. You can see the galaxy’s bar (outlined by a thick, solid purple line in the center image, while the spiral arms appear as faint purple lines). Credit: Zoe Le Conte

“The simulations of the universe now need to be examined closely to see if we get the same results as the observations we made with James Webb,” Gadotti added. “We have to think beyond what we thought we knew.”

As the researchers looked further back in time, they could see fewer and fewer bar-forming galaxies. They say this may be because galaxies may not have formed as well at an even earlier stage in the universe. There’s also currently no way to see shorter bars of stars, which are less easy to spot even with the JWST’s greater telescopic power.

James Webb space telescope Art

Artist’s impression of the James Webb Space Telescope, with the primary mirror pointing towards the cosmos. Credit: TRW-Ball

Future directions

The researchers say they now want to investigate even more galaxies in the early universe to see if they also formed bars. They hope to eventually be able to look further back in time – 12.2 billion years – to look at growth over time and the mechanisms behind this growth.

Reference: “A JWST study of the rod fraction at redshifts 1 ≤ z ≤ 3” by Zoe A Le Conte, Dimitri A Gadotti, Leonardo Ferreira, Christopher J Conselice, Camila de Sá-Freitas, Taehyun Kim, Justus Neumann, Francesca Fragkoudi, E Athanassoula and Nathan J Adams, April 23, 2024, Monthly notices of the Royal Astronomical Society.
DOI: 10.1093/mnras/stae921

The Center for Extragalactic Astronomy and the Center for Advanced Instrumentation at Durham University made significant contributions to the development of the JWST. The latest study also involved scientists from the Institute for Computational Cosmology at Durham University, University of Victoria, Canada; Jodrell Bank Center for Astrophysics – University of Manchester, UK; the European Southern Observatory; the Department of Astronomy and Atmospheric Sciences, Kyungpook National University, Republic of Korea; the Max Planck Institute for Astronomy, Germany; University of Aix Marseille, France. The research was funded in Great Britain by the UKRI-Science and Technology Facilities Council.

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