Using the James Webb Space Telescope, astronomers have for the first time observed a galaxy in the early universe growing from the inside out, a mere 700 million years after the Big Bang.
This galaxy, significantly smaller yet more mature than expected, demonstrates unique growth patterns with its dense core and rapidly forming star outskirts.
Astronomers have employed the NASA/ESA James Webb Space Telescope (JWST) to observe the ‘inside-out’ growth of a galaxy in the early universe, a mere 700 million years after the Big Bang.
This galaxy is one hundred times smaller than the Milky Way, yet it is surprisingly mature for so early in the universe. Like a large city, this galaxy features a densely packed core of stars but becomes sparser in the galactic ‘suburbs’. And like a large city, this galaxy is starting to sprawl, with star formation accelerating in the outskirts.
This is the earliest-ever detection of inside-out galactic growth. Until Webb, it had not been possible to study galaxy growth so early in the universe’s history. Although the images obtained with Webb represent a snapshot in time, the researchers, led by the University of Cambridge, say that studying similar galaxies could help us understand how they transform from clouds of gas into the complex structures we observe today. The results are reported today (October 11) in the journal Nature Astronomy.
New Insights Into Early Galactic Evolution
“The question of how galaxies evolve over cosmic time is an important one in astrophysics,” said co-lead author Dr. Sandro Tacchella from Cambridge’s Cavendish Laboratory. “We’ve had lots of excellent data for the last ten million years and for galaxies in our corner of the universe, but now with Webb, we can get observational data from billions of years back in time, probing the first billion years of cosmic history, which opens up all kinds of new questions.”
The galaxies we observe today grow via two main mechanisms: either they pull in, or accrete, gas to form new stars, or they grow by merging with smaller galaxies. Whether different mechanisms were at work in the early universe is an open question which astronomers are hoping to address with Webb.
“You expect galaxies to start small as gas clouds collapse under their own gravity, forming very dense cores of stars and possibly black holes,” said Tacchella. “As the galaxy grows and star formation increases, it’s sort of like a spinning figure skater: as the skater pulls in their arms, they gather momentum, and they spin faster and faster. Galaxies are somewhat similar, with gas accreting later from larger and larger distances spinning the galaxy up, which is why they often form spiral or disc shapes.”
Observing Star Formation in the Early Universe
This galaxy, observed as part of the JADES (JWST Advanced Extragalactic Survey) collaboration, is actively forming stars in the early universe. It has a highly dense core, which despite its relatively young age, is of a similar density to present-day massive elliptical galaxies, which have 1000 times more stars. Most of the star formation is happening further away from the core, with a star-forming ‘clump’ even further out.
The star formation activity is strongly rising toward the outskirts, as the star formation spreads out and the galaxy grows in size. This type of growth had been predicted with theoretical models, but with Webb, it is now possible to observe it.
“One of the many reasons that Webb is so transformational to us as astronomers is that we’re now able to observe what had previously been predicted through modeling,” said co-author William Baker, a PhD student at the Cavendish. “It’s like being able to check your homework.”
Advances in Galactic Research with Webb
Using Webb, the researchers extracted information from the light emitted by the galaxy at different wavelengths, which they then used to estimate the number of younger stars versus older stars, which is converted into an estimate of the stellar mass and star formation rate.
Because the galaxy is so compact, the individual images of the galaxy were ‘forward modeled’ to take into account instrumental effects. By using stellar population modeling that includes prescriptions for gas emission and dust absorption, the researchers found older stars in the core, while the surrounding disc component is undergoing very active star formation. This galaxy doubles its stellar mass in the outskirts roughly every 10 million years, which is very rapid: the Milky Way galaxy doubles its mass only every 10 billion years.
The density of the galactic core, as well as the high star formation rate, suggest that this young galaxy is rich with the gas it needs to form new stars, which may reflect different conditions in the early universe.
“Of course, this is only one galaxy, so we need to know what other galaxies at the time were doing,” said Tacchella. “Were all galaxies like this one? We’re now analyzing similar data from other galaxies. By looking at different galaxies across cosmic time, we may be able to reconstruct the growth cycle and demonstrate how galaxies grow to their eventual size today.”
Reference: “A core in a star-forming disc as evidence of inside-out growth in the early Universe” by William M. Baker, Sandro Tacchella, Benjamin D. Johnson, Erica Nelson, Katherine A. Suess, Francesco D’Eugenio, Mirko Curti, Anna de Graaff, Zhiyuan Ji, Roberto Maiolino, Brant Robertson, Jan Scholtz, Stacey Alberts, Santiago Arribas, Kristan Boyett, Andrew J. Bunker, Stefano Carniani, Stephane Charlot, Zuyi Chen, Jacopo Chevallard, Emma Curtis-Lake, A. Lola Danhaive, Christa DeCoursey, Eiichi Egami, Daniel J. Eisenstein, Ryan Endsley, Ryan Hausen, Jakob M. Helton, Nimisha Kumari, Tobias J. Looser, Michael V. Maseda, Dávid Puskás, Marcia Rieke, Lester Sandles, Fengwu Sun, Hannah Übler, Christina C. Williams, Christopher N. A. Willmer and Joris Witstok, 11 October 2024, Nature Astronomy.
DOI: 10.1038/s41550-024-02384-8
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5 Comments
That seems like what a naive growth model from infalling gas would have it.
One example of the spinning up scenario is that some early compact galaxies – the “little red dots [LRDs]” – had huge gas spin rates.
“The objects are spinning super fast, Dale Kocevski(opens a new tab) of Colby College told me — gas in the clouds is being flung around at 3,000 kilometers per hour. Typical gas flow is about 300 kilometers per hour. Only something huge can accelerate gas to those speeds, so some people argue the LRDs contain spinning supermassive black holes.
“But there are ways out of it,” countered Erica Nelson of the University of Colorado, Boulder. Her presentation described how, if LRDs are really tight, compact balls of gas, the gas might actually spin around that quickly. ”
[“The ‘Beautiful Confusion’ of the First Billion Years Comes Into View”, Rebecca Boyle, October 9, 2024, Quanta Magazine]
The authors are right,a hypothesis is present according to the Principle for observation of only stars of a galaxy solely from the earth;noted that JWST is placed at a specific position,where gravity of the earth and the sun balances to each other.
Thus,the Coevolution Theory of supermassive black hole at the center of galaxy and stars due to rotation,in the modified version of the Dynamic Big Bang,is in progress with different observations in parts.
The Theory of Coevolution of supermassive black hole at the center of galaxy and stars in the new Dynamic version of the Big Bang due to rotation of galaxy along the Time axis,explains all early universe up to 1 billion years from the origin.This follows the Octet Rule;where,one octet is defined by 8 ×(125 + or _ 25) million years and is broadly divided in to two equal parts.
Thanks to the aithors for invaluable experimental work done with JWST for an early galaxy,present 700 million years after the big bang to establish a hypothesis.For a similar or linked hypothesis,as presented here,a statistical fluke of an order is present to transform as a theory;so,this difference must be accounted for,in order to obtain good result in the calculation.