Astronomers using the NASA/ESA/CSA James Webb Space Telescope have spotted early 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.
“Stellar bars play a central role in the secular evolution of galaxies by efficiently redistributing mass and angular momentum and driving gas inflows into the circumnuclear region through gravitational torques and shocks,” said University of Texas at Austin’s Professor Shardha Jogee and colleagues.
“Most present-day spirals are barred, including our own Milky Way Galaxy.”
“Observational evidence in nearby galaxies suggests bars influence their central molecular gas concentrations, velocity fields of ionized gas, star formation activity, and central bulges.”
In the new study, the astronomers focused on a sample of 348 galaxies in the early Universe.
The observations were made as part of the Cosmic Evolution Early Release Science Survey (CEERS).
They were able to detect stellar bars in six galaxies: two galaxies from about 11 billion years ago and four galaxies from more than 8 billion years ago.
Prior to Webb, images from the NASA/ESA Hubble Space Telescope had never detected bars at such young epochs.
“I took one look at these data, and I said, ‘We are dropping everything else!’” Professor Jogee said.
“The bars hardly visible in Hubble data just popped out in the Webb image, showing the tremendous power of Webb to see the underlying structure in galaxies.”
“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, so everything is new. It’s like going into a forest that nobody has ever gone into,” said Yuchen ‘Kay’ Guo, a graduate student at the University of Texas at Austin.
“Bars solve the supply chain problem in galaxies,” Professor 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.”
“The discovery of bars during such early epochs shakes up galaxy evolution scenarios in several ways.”
“This discovery of early bars means galaxy evolution models now have a new pathway via bars to accelerate the production of new stars at early epochs.”
The study was published in the Astrophysical Journal Letters.
Yuchen Guo et al. 2023. First Look at z > 1 Bars in the Rest-Frame Near-Infrared with JWST Early CEERS Imaging. ApJL, in press; arXiv: 2210.08658
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