This simulation shows both how star bars form (left) and bar-driven gas inlets (right). Star bars play an important role in galaxy evolution by flowing gas into the central regions of a galaxy, where gas is rapidly converted into new stars at a rate typically 10 to 100 times faster than the rest of the galaxy. The rods also indirectly help supermassive black holes grow at the centers of galaxies by channeling the gas portion of the path. Credits: Françoise Combes, Paris Observatory
new images[{” attribute=””>NASA’s James Webb Space Telescope (JWST) reveal for the first time galaxies with stellar bars — elongated features of stars stretching from the centers of galaxies into their outer disks — at a time when the universe was a mere 25% of its present age. The finding of so-called barred galaxies, similar to our Milky Way, this early in the universe will require astrophysicists to refine their theories of galaxy evolution.
Prior to JWST, images from the Hubble Space Telescope had never detected bars at such young epochs. In a Hubble image, one galaxy, EGS-23205, is little more than a disk-shaped smudge, but in the corresponding JWST image taken this past summer, it’s a beautiful spiral galaxy with a clear stellar bar.
“I took one look at these data, and I said, ‘We are dropping everything else!’” said Shardha Jogee, professor of astronomy at The University of Texas at Austin. “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,” she said, describing data from the Cosmic Evolution Early Release Science Survey (CEERS), led by UT Austin professor, Steven Finkelstein.
The power of JWST to map galaxies at high resolution and at longer infrared wavelengths than Hubble allows it look through dust and unveil 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 disk-shaped smudge obscured by dust and impacted by the glare of young stars, but in the corresponding JWST mid-infrared image (taken this past summer), it’s a beautiful spiral galaxy with a clear stellar bar. Credit: NASA/CEERS/University of Texas at Austin
The team identified another barred galaxy, EGS-24268, also from about 11 billion years ago, which makes two barred galaxies existing farther back in time than any previously discovered.
In an article 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 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.”
Bars play an important role in galaxy evolution by funneling gas into the central regions, boosting star formation.
“Bars solve the supply chain problem in galaxies,” Jogee said. “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.”
Bars also help to grow supermassive black holes in the centers of galaxies by channeling the gas part of the way.
This simulation shows both how star bars form (left) and bar-driven gas inlets (right). Star bars play an important role in galaxy evolution by flowing gas into the central regions of a galaxy, where gas is rapidly converted into new stars at a rate typically 10 to 100 times faster than the rest of the galaxy. The rods also indirectly help supermassive black holes grow at the centers of galaxies by channeling the gas portion of the path. Credits: Françoise Combes, Paris Observatory
The discovery of rods in such early times is shaking up galaxy evolution scenarios in several ways.
“This discovery of early rods means that models of galaxy evolution now have a new way through rods to accelerate the production of new stars in the early stages,” said Jogee. Said.
And the existence of these first bars defies theoretical models because they need to get galaxy physics right to accurately predict the abundance of bars. The team will test different models in their next article.
Assembly of JWST images showing six sample barred galaxies, two of which represent the highest reexamination times quantitatively identified and characterized to date. Labels in the upper left of each figure indicate the reexamination time of each galaxy, ranging from 8.4 to 11 billion years ago (Gyr), when the universe was only 40% to 20% of its current age. Credit: NASA/CEERS/University of Texas at Austin
JWST can reveal structures in distant galaxies better than Hubble for two reasons: First, its larger mirror gives it the ability to gather more light, allowing it to see farther and at higher resolution. Second, because it observes at longer infrared wavelengths, it can see behind the dust better than Hubble.
Undergraduate students Eden Wise and Zilei Chen played an important role in the research by visually examining hundreds of galaxies, looking for those that appear to have bars; approach.
Reference: “First Look at z > 1 Bars in Rest-Frame Near-Infrared with JWST Early CEERS Imaging” by Yuchen Guo, Shardha Jogee, Steven L. Finkelstein, Zilei Chen, Eden Wise, Micaela B. Bagley, Guillermo Barro, Stijn Wuyts, Dale D. Kocevski, Jeyhan S. Kartaltepe, Elizabeth J. McGrath, Henry C. Ferguson, Bahram Mobasher, Mauro Giavalisco, Ray A. Lucas, Jorge A. Zavala, Jennifer M. Lotz, Norman A. Grogin, Marc Huertas -Company, Jesús Vega-Ferrero, Nimish P. Hathi, Pablo Arrabal Haro, Mark Dickinson, Anton M. Koekemoer, Casey Papovich, Nor Pirzkal, LY Aaron Yung, Bren E. Backhaus, Eric F. Bell, Antonello Calabrò, Nikko J Cleri, Rosemary T. Coogan, MC Cooper, Luca Costantin, Darren Croton, Kelcey Davis, Alexander de la Vega, Avishai Dekel, Maximilien Franco, Jonathan P. Gardner, Benne W. Holwerda, Taylor A. Hutchison, Viraj Pandya, Pablo G. Pérez-González, Swara Ravindranath, Caitlin Rose, Jonathan R. Trump and Weichen Wang, Accepted, Astrophysical Journal Letters.
arXiv:2210.08658
Other co-authors from UT Austin are Steven Finkelstein, Micaela Bagley and Maximilien Franco. Dozens of co-authors from other institutions come from the US, UK, Japan, Spain, France, Italy, Australia and Israel.
This research was funded in part by the Roland K. Blumberg Foundation for Astronomy, the Heising-Simons Foundation, and NASA. This work relied on resources at the Texas Advanced Computing Center, including Frontera, the most powerful supercomputer at a US university.
