Webb Depicts Staggering Structure in 19 Nearby Spiral Galaxies

January 29, 2024

The scientific collaboration PHANGS (Physics at High Angular resolution in Nearby GalaxieS), led by Eva Schinnerer, an astronomer at the Max Planck Institute for Astronomy (MPIA) in Heidelberg, Germany, today released stunning pictures of 19 nearby galaxies taken with the James Webb Space Telescope (JWST). These images are made from infrared light and provide a detailed view of the distribution of stars and the material from which they are born. The data is now publicly available to astronomers worldwide to boost the research into galaxies, particularly the formation of their stars.

It’s oh-so-easy to be absolutely mesmerised by these spiral galaxies. Follow their clearly defined arms, which are brimming with stars, to their centres, where there may be old star clusters and – sometimes – active supermassive black holes. Only the JWST can deliver highly detailed scenes of nearby galaxies in a combination of near- and mid-infrared light – and they were publicly released today.

JWST’s images are part of a large, long-standing project, the Physics at High Angular resolution in Nearby GalaxieS (PHANGS) program, supported by more than 150 astronomers worldwide. Before JWST took these images, PHANGS was already crammed with data from the Hubble Space Telescope (HST), the Very Large Telescope’s (VLT) Multi-Unit Spectroscopic Explorer (MUSE), and the Atacama Large Millimeter/submillimeter Array (ALMA), including observations in ultraviolet, visible, and radio light. JWST’s near- and mid-infrared contributions have provided several new puzzle pieces.

“Webb’s new images are extraordinary,” said Janice Lee, a project scientist for strategic initiatives at the Space Telescope Science Institute (STScI) in Baltimore, USA. “They’re mind blowing even for researchers who have studied galaxies for decades. Bubbles and filaments are resolved down to the smallest scales ever observed and tell a story about the star formation cycle.”

Excitement rapidly spread throughout the team as the images flooded in. “I feel like our team lives in a constant state of being overwhelmed – in a positive way – by the amount of detail in these images,” added Thomas Williams, a postdoctoral researcher at the University of Oxford in the United Kingdom and a former post-doc at MPIA.

Follow the Spiral Arms

JWST’s NIRCam (Near-Infrared Camera) captured millions of stars in these images, which sparkle in blue tones. Some stars are spread throughout the spiral arms, but others are clumped tightly together in star clusters.

The telescope’s MIRI (Mid-Infrared Instrument) data highlights glowing dust, showing us where it exists behind, around, and between stars. It also spotlights stars that have not yet fully formed – they are still encased in the gas and dust that feed their growth, like bright red seeds at the tips of dusty peaks. “These are where we can find the newest, most massive stars in the galaxies,” said Erik Rosolowsky, a professor of physics at the University of Alberta in Edmonton, Canada.

MPIA engineers, supported by Hensoldt in Oberkochen, Germany, developed, among other parts, a filter wheel for the MIRI camera that now produces these fantastic pictures. “We are proud to have contributed to MIRI’s overwhelming success. These marvellous pictures are the reward for decades filled with hard work,” said MPIA’s Oliver Krause. He is the head of the research group for Infrared Space Astronomy at MPIA and responsible for the institute’s technical contributions to the JWST.

Selected Webb Images

Something else that knocked astronomers out of their chairs? JWST’s images show large, spherical shells in the gas and dust. “These holes may have been created by one or more stars that exploded, carving out giant holes in the interstellar material,” explained Adam Leroy, a professor of astronomy at the Ohio State University in the US. “We only see these relics in JWST’s images.”

Now, trace the spiral arms to find extended regions of gas that appear red and orange. “These structures tend to follow the same pattern in certain parts of the galaxies,” Rosolowsky added. “We think of these like waves, and their spacing tells us a lot about how a galaxy distributes its gas and dust.” Studying these structures will provide crucial insights into how galaxies build, maintain, and shut off star formation.

Dive into the Interior

Evidence shows that galaxies grow from inside out – star formation begins at galaxies’ cores and spreads along their arms, spiralling away from the centre. The farther a star is from the galaxy’s core, the more likely it is to be younger. In contrast, the areas near the cores that look lit by a blue spotlight are populations of older stars.

What about galaxy cores that are awash in pink-and-red diffraction spikes? They appear when light from bright and compact objects enter the telescope and hits structures such as the secondary mirror mount. “That’s a clear sign that there may be an active supermassive black hole,” said MPIA research group leader Eva Schinnerer, the PI of the PHANGS collaboration. “Or, the star clusters toward the centre are so bright that they have saturated that area of the image.”

Research Galore

There are practically endless questions researchers can begin to answer with the combined PHANGS data. Still, the unprecedented number of stars JWST resolved is a great place to begin. “Stars can live for billions or trillions of years,” Leroy said. “By precisely cataloguing all types of stars, we can build a more reliable, holistic view of their life cycles.”

In addition to immediately releasing the images, the PHANGS team has released the largest catalogue of roughly 100,000 star clusters to date. “The amount of analysis that can be done with these images is vastly larger than anything our team could possibly handle,” Rosolowsky emphasised. “We’re excited to support the community so all researchers can contribute.”

Additional Information

MPIA scientists involved in the PHANGS project are Eva Schinnerer (PHANGS Lead), Nadine Neumayer (MPIA Lise Meitner Group Lead), Franziska Bruckmann, Stephen Hannon, Jonathan Henshaw, Nils Hoyer, Justus Neumann, and Sophia Stuber.

The James Webb Space Telescope is the world’s premier space science observatory. JWST is solving mysteries in our solar system, looking beyond to distant worlds around other stars, and probing our universe’s mysterious structures and origins and our place in it. It is an international program led by NASA with its partners, ESA (European Space Agency) and the Canadian Space Agency (CSA).

The MIRI consortium consists of personnel from the ESA member states Belgium, Denmark, France, Germany, Ireland, the Netherlands, Spain, Sweden, Switzerland, and the United Kingdom.

The consortium’s work is funded by the national science organisations – in Germany by the Max Planck Society (MPG) and the German Aerospace Center (DLR). The participating German institutions are the Max Planck Institute for Astronomy in Heidelberg, the University of Cologne, and Hensoldt AG in Oberkochen, formerly Carl Zeiss Optronics.

This press release was adapted from the original version published by STScI.

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