“Teenage Galaxies” Unveiled: Webb Space Telescope’s Remarkable Glimpse Into the Early Universe

Studying “teenage galaxies” from the ancient universe can teach scientists about how these massive systems of stars mature and evolve.

Galaxies that formed just 2 to 3 billion years after the Big BangThe Big Bang is the leading cosmological model explaining how the universe as we know it began approximately 13.8 billion years ago.” data-gt-translate-attributes=”[{“attribute”:”data-cmtooltip”, “format”:”html”}]”>Big Bang are unusually hot and glow with light from surprising elements, like nickel, according to new work led by Carnegie’s Gwen Rudie and Northwestern UniversityEstablished in 1851, Northwestern University (NU) is a private research university based in Evanston, Illinois, United States. Northwestern is known for its McCormick School of Engineering and Applied Science, Kellogg School of Management, Feinberg School of Medicine, Pritzker School of Law, Bienen School of Music, and Medill School of Journalism. ” data-gt-translate-attributes=”[{“attribute”:”data-cmtooltip”, “format”:”html”}]”>Northwestern University’s Allison Strom. Studying “teenage galaxies” from the ancient universe can teach scientists about how these massive systems of stars mature and evolve.

Their findings, published in The Astrophysical Journal LettersThe Astrophysical Journal Letters (ApJL) is a peer-reviewed scientific journal that focuses on the rapid publication of short, significant letters and papers on all aspects of astronomy and astrophysics. It is one of the journals published by the American Astronomical Society (AAS), and is considered one of the most prestigious journals in the field.” data-gt-translate-attributes=”[{“attribute”:”data-cmtooltip”, “format”:”html”}]”>Astrophysical Journal Letters, are part of the CECILIA (Chemical Evolution Constrained using Ionized Lines in Interstellar Aurorae) survey, developed by Rudie and Strom—a former Carnegie postdoc. Last July, they pointed NASA’s James Webb Space Telescope (JWST) at 33 specially selected ancient galaxies whose light traveled more than 10 billion years to reach us and stared with the new telescope for more than a day, providing the most detailed view of these early galaxies yet captured.

JWST telescope image of a galaxy cluster known as “El Gordo,” which is an example of a “cosmic teenager.” Credit: NASA, ESA, CSA, Jose M. Diego (IFCA), Brenda Frye (University of Arizona), Patrick Kamieneski (ASU), Tim Carleton (ASU), Rogier Windhorst (ASU), Alyssa Pagan (STScI), Jake Summers (ASU), Jordan C. J. D’Silva (UWA), Anton M. Koekemoer (STScI), Aaron Robotham (UWA), Rogier Windhorst (ASU)

Star Formation and Galactic Evolution

In the universe’s youth, many galaxies, including the 33 chosen for this study, experienced a period of intense star formation. Today, some galaxies, such as our own Milky WayThe Milky Way is the galaxy that contains our Solar System and is part of the Local Group of galaxies. It is a barred spiral galaxy that contains an estimated 100-400 billion stars and has a diameter between 150,000 and 200,000 light-years. The name "Milky Way" comes from the appearance of the galaxy from Earth as a faint band of light that stretches across the night sky, resembling spilled milk.” data-gt-translate-attributes=”[{“attribute”:”data-cmtooltip”, “format”:”html”}]”>Milky Way, still form new stars, albeit not as rapidly. Other galaxies have stopped forming stars altogether. This new work can help astronomers understand the reasons behind these different trajectories.

“We’re trying to understand how galaxies grew and changed over the 14 billion years of cosmic history,” said first author Allison Strom. “Using the JWST, our program targets teenage galaxies when they were going through a messy time of growth spurts and change. Teenagers often have experiences that determine their trajectories into adulthood. For galaxies, it’s the same.”

Observations by NASA’s James Webb Space Telescope were crucial to this research. Credit: NASA

Spectral Analysis and Elemental Discoveries

The CECILIA team studied the spectra from these distant galaxies, separating their light into its component wavelengths, just as a prism spreads sunlight into the colors of the rainbow. Looking at the light in this way helps astronomers measure the temperature and chemical composition of cosmic sources.

“We averaged together the spectra from all 33 galaxies to create the deepest spectrum of a distant galaxy ever seen—which it would take 600 hours of telescope time to replicate,” Rudie explained. “This enabled us to create an atlas, of sorts, that will inform future JWST observations of very distant objects.”

Using the spectra, the researchers were able to identify eight distinct elements: Hydrogen, helium, nitrogen, oxygen, silicon, sulfur, argon, and nickel.

“These elements existing in these galaxies is not a surprise, but our ability to measure their light is unprecedented and shows the power of JWST,” said Rudie.

All elements that are heavier than hydrogen and helium form inside stars. When stars explode in violent events like supernovae, they spew these elements out into the cosmic surroundings, where they are incorporated into the next stellar generation. So, by revealing the presence of certain elements in these early galaxies, astronomers can learn about how star formation changes over the course of their evolution.

The CECILIA team was surprised by the presence of nickel, which is particularly difficult to observe.

“Never in my wildest dreams did I imagine we would see nickel,” Strom said. “Even in nearby galaxies, people don’t observe this. There has to be enough of an element present in a galaxy and the right conditions to observe it. No one ever talks about observing nickel. Elements have to be glowing in gas in order for us to see them. So, in order for us to see nickel, there may be something unique about the stars within the galaxies.”

“JWST is still a very new observatory,” added co-author Ryan Trainor of Franklin & Marshall College. “Astronomers around the world are still trying to figure out the best ways to analyze the data we receive from the telescope.”

Temperature Findings and Legacy

Another surprise: The teenage galaxies were extremely hot. By examining the spectra, physicists can calculate a galaxy’s temperature. While the hottest pockets with galaxies can reach over 9,700 degrees CelsiusThe Celsius scale, also known as the centigrade scale, is a temperature scale named after the Swedish astronomer Anders Celsius. In the Celsius scale, 0 °C is the freezing point of water and 100 °C is the boiling point of water at 1 atm pressure.” data-gt-translate-attributes=”[{“attribute”:”data-cmtooltip”, “format”:”html”}]”>Celsius or 17,492 degrees FahrenheitThe Fahrenheit scale is a temperature scale, named after the German physicist Daniel Gabriel Fahrenheit and based on one he proposed in 1724. In the Fahrenheit temperature scale, the freezing point of water freezes is 32 °F and water boils at 212 °F, a 180 °F separation, as defined at sea level and standard atmospheric pressure. ” data-gt-translate-attributes=”[{“attribute”:”data-cmtooltip”, “format”:”html”}]”>Fahrenheit, the teenage galaxies clock in at higher than 13,350 degrees Celsius or 24,062 degrees Fahrenheit.

“We expected these early galaxies to have very, very different chemistry from our own Milky Way and the galaxies that surround us today,” Rudie said. “But we were still surprised by what JWST revealed.”

The project was named in honor of Cecilia Payne-Gaposchkin, who did pioneering work on the chemistry of our Sun nearly 100 years ago. Her findings upended the scientific community’s understanding of the Sun’s composition, and she faced unfair criticism for years before her breakthrough work was finally recognized.

“Naming our JWST survey after Cecilia Payne was intended to pay homage to her pioneering studies of the chemical makeup of stars. Allison and I recognize that our own work revealing the chemistry of these very early galaxies is built upon her legacy.” Rudie said.

CECILIA was the first of six initial JWST projects led by Carnegie and Carnegie-affiliated astronomers selected to make observations using the incredible space telescope. Earlier this year, another four Carnegie-led initiatives were chosen for the second cycle of JWST time allocations.

For more on this research, see Webb Reveals “Teenage Galaxies” Are Unusually Hot, Glowing With Unexpected Elements.

Reference: “CECILIA: The Faint Emission Line Spectrum of z ∼ 2–3 Star-forming Galaxies” by Allison L. Strom, Gwen C. Rudie, Ryan F. Trainor, Gabriel B. Brammer, Michael V. Maseda, Menelaos Raptis, Noah S. J. Rogers, Charles C. Steidel, Yuguang Chen, 昱光 陈 and David R. Law, 20 November 2023, The Astrophysical Journal Letters.
DOI: 10.3847/2041-8213/ad07dc

This work was supported by NASAEstablished in 1958, the National Aeronautics and Space Administration (NASA) is an independent agency of the United States Federal Government that succeeded the National Advisory Committee for Aeronautics (NACA). It is responsible for the civilian space program, as well as aeronautics and aerospace research. Its vision is "To discover and expand knowledge for the benefit of humanity." Its core values are "safety, integrity, teamwork, excellence, and inclusion." NASA conducts research, develops technology and launches missions to explore and study Earth, the solar system, and the universe beyond. It also works to advance the state of knowledge in a wide range of scientific fields, including Earth and space science, planetary science, astrophysics, and heliophysics, and it collaborates with private companies and international partners to achieve its goals.” data-gt-translate-attributes=”[{“attribute”:”data-cmtooltip”, “format”:”html”}]”>NASA, the Pittsburgh Foundation, and the Research Corporation for Scientific Advancement. The data were obtained from the Mikulski Archive for Space Telescopes at the Space Telescope Science Institute and from the W.M. Keck Observatory.