Distant star cradles

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The James Webb Space Telescope Reveals Star Formation in Gas and Dust Networks of Other Galaxies

NGC 1365 is a very active barred spiral galaxy at a distance of 64 million light
NGC 1365 is a very active barred spiral galaxy at a distance of 64 million light years. Gas and dust along the bar connect the spiral arms to the galactic center. The bar is constantly feeding new gas into the galaxy’s core, driving ongoing star formation there. The image is composed in the same way as described for NGC 628. NASA / ESA / CSA / Judy Schmidt (CC BY 2.0)

Even the first images from the James Webb Space Telescope are helping to clarify questions about how stars form in relatively nearby galaxies. Data from the powerful infrared telescope are revealing to scientists previously hidden regions where new stars are born. These images provide the first clues about how networks of gas and dust become the site of active star formation.

Astronomers from around the world, including scientists from the Max Planck Institute for Astronomy, aim to unravel some of the last mysteries of star formation in galaxies. The study, called Physics at High Angular Resolution in Nearby Galaxies with JWST (Phangs-JWST), led by Janice Lee, principal investigator of the Gemini Observatory at the National Science Foundation’s NOIRLab in Tucson, Arizona, USA, analyzes images from the James Webb Space Telescope. The team’s latest results were recently published in a special issue of the Astrophysical Journal Letters.

Four galaxies in new light

In its first months of science operation, the James Webb Telescope (JWST) has observed four of the 19 planned galaxies in relative proximity to the Milky Way in the infrared wavelength range. These are consistently galaxies that we see from above or below. More precisely, they are the objects NGC 628 (M 74), NGC 1365, NGC 7496, and IC 5332. "We are particularly proud of the major technical contributions of the Max Planck Institute for Astronomy to one of the infrared cameras used, Miri, such as the filter wheel mechanism of the imaging camera," says Eva Schinnerer, group leader at the institute. She leads the overall Phangs collaboration. The Miri images reveal a network of highly structured details in these galaxies, such as bar structures that funnel gas into the centers of the galaxies, fueling the formation of new stars.

The clarity with which we see the fine structures really surprised us," says Adam Leroy of Ohio State University, USA, and Humboldt Research Award winner at the Max Planck Institute for Astronomy. "The new Phangs JWST data give us a fascinating insight into the star formation of surrounding spiral galaxies at the highest resolution," explains Nadine Neumayer, head of a Lise Meitner research group at the Max Planck Institute. The infrared images complement existing Hubble Space Telescope data from the optical spectral range.

For years, the Phangs team used Hubble images, among others, to study how these galaxies look in optical or ultraviolet light. But in the process, they saw only gas and dust in the regions where the stars form, because the light from the new stars does not penetrate outward from these birth cocoons. The crucial early phase in the life cycle of a star thus remained hidden from view from Earth. Infrared light, on the other hand, can penetrate the dust. The James Webb Space Telescope, which is very powerful in the infrared range, now makes it possible to visualize the missing pieces of the stellar birth puzzle.

Fine networks of star formation

The images reveal subtle, never-before-seen structures, such as in the center of NGC 628, that the team cannot yet explain. "The new perspective that JWST gives us on the centers of galaxies contributes fundamentally to our understanding of the evolution of star clusters and galaxies," says Nils Hoyer, a doctoral student at the Max Planck Institute for Radio Astronomy and the University of Heidelberg. "With the JWST, we can precisely locate the youngest stars still in their birth clouds in nearby galaxies," Schinnerer adds. In addition, the researchers can trace where and how incoming gas is converted into stars, such as in NGC 1365, and then compare these findings with the corresponding processes in the Milky Way. In addition, at the center of the galaxy NGC 628, the observations reveal a very massive and tightly packed star cluster. Overall, the new data already show a wide variety from amazingly quiet to dense and massive regions with episodes of very active star formation.

The astronomers also discovered how stars form not only in the spiral arms, but also between them. "By using JWST, we were finally able to detect the young stars in fine extensions of gas, called spurs, that extend from the spiral arms," explains Tom Williams, a former astronomer at the Max Planck Institute for Astronomy. "Our earlier observations had already indicated that this might be the case. The first results show that, as expected, the star formation rate is higher in the spiral arms because there is more gas and dust. However, the efficiency with which stars are formed from them appears to be constant throughout the Galactic disk.

James Webb’s images are available to all research teams and also to the public. The Phangs team is working to increase the value of these images to the astronomical community by matching them with complementary images from other observatories. The quality of the data opens the door to an even more comprehensive understanding of how small-scale processes of the intricate web of dust and gas and large-scale galaxy evolution and structure interact.

PHANGS-JWST First Results: Spurring on Star Formation: JWST Reveals Localized Star Formation in a Spiral Arm Spur of NGC 628