The Webb Space Telescope rewrites the rules of galactic evolution

Findings from the James Webb Space Telescope suggest that early galaxies were forming complex bar-like structures much earlier, indicating accelerated evolution. Credit: SciTechDaily

Advanced observations from JWST show that early galaxies matured faster and were less chaotic, challenging previous theories of galaxy evolution.

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

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

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

Insights from the James Webb Space Telescope

Bars are elongated bands of stars found in disk or spiral galaxies like our own Milky Way. As bars develop, they regulate star formation within a galaxy, pushing gas into the central region of the galaxy. Their presence tells scientists that galaxies have entered a settled and mature stage.

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

A grayscale image of the galaxy EGS_31125 at 10.6 billion years ago, visually classified as strongly barred (depicted in the central image as a thick solid purple line with the spiral arms shown as faint purple lines). 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, particularly in the context of bars. Credit: Zoe Le Conte

“Galaxies in the early Universe are maturing much faster than we thought. This is a real surprise because you would expect the Universe at that stage to be very turbulent with lots of collisions between galaxies and lots of gas that has not yet turned into stars,” explained lead author Zoe Le Conte, a Ph.D. at the Center for Extragalactic Astronomy, Department of Physics, Durham University.

“However, thanks The James Webb Space Telescope we are seeing many of these bars much earlier in the life of the Universe which means the galaxies were at a more established stage in their evolution than previously thought,” she adds. The researchers say that this new evidence suggests that theories about the early evolution of the galaxy may need significant revisions.

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

Research Methodology and Findings

Researchers used JWST to look for the formation of bars in galaxies, as they would have been seen between 8 and 11.5 billion years ago. The Universe itself is 13.7 billion years old. Of the 368 disc galaxies observed, the researchers found that almost 20 percent had bars—twice as many as observed by Hubble.

Co-author Dr. Dimitri Gadotti, at the Center for Extragalactic Astronomy, Department of Physics, Durham University, said: “We find that many more bars were present in the early Universe than previously found in Hubble studies, implying that the galaxy driven by rod evolution has been occurring for much longer than previously thought.”

A grayscale image of the galaxy EGS_31125 at 10.6 billion years ago as seen by the James Webb Space Telescope. The galaxy bar can be seen (outlined in the central image as a thick solid purple line with the spiral arms shown as faint purple lines). Credit: Zoe Le Conte

“Simulations of the Universe must now be examined to see if we get the same results as the observations we made with James Webb,” Gadotti adds. “We have to think outside of what we thought we knew.”

As the researchers looked further back in time, they were able to see fewer and fewer galaxies forming bars. They say this may be because galaxies in an even earlier stage of the Universe may not be as well formed. Also, there is currently no way to see shorter bands of stars, which are less easy to spot, even with the increased telescopic power provided by JWST.

Artist’s impression of the James Webb Space Telescope showing its main mirror pointed into space. Credit: TRW-Ball

Future directions

The researchers say they now want to probe even more galaxies in the early Universe to see if they also formed bars. They hope to eventually look further back in time – 12.2 billion years – to see the increase in levels over time and what mechanisms are behind this increase.

Reference: “A JWST investigation of the bar 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 E Athanassoula and Nathan J Adams, 23 April 2024, Monthly Notices of the Royal Astronomical Society.
DOI: 10.1093/mnras/stae921

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