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Webb depicts staggering structure in 19 nearby spiral galaxies

A new treasure trove of images from the NASA/ESA/CSA James Webb Space Telescope showcases near- and mid-infrared portraits of 19 face-on spiral galaxies. This new set of exquisite images show stars, gas, and dust on the smallest scales ever observed beyond our own galaxy. Teams of researchers are studying these images to uncover the origins of these intricate structures. The research community’s collective analysis will ultimately inform theorists’ simulations, and advance our understanding of star formation and the evolution of spiral galaxies.

19 Nineteen Webb images of face-on spiral galaxies are combined in a mosaic, some within squares, and others horizontal or vertical rectangles. Galaxies’ spiral arms appear in shades of orange, and many of their centres have light blue hazes.
This collection of 19 face-on spiral galaxies from the NASA/ESA/CSA James Webb Space Telescope in near- and mid-infrared light is at once overwhelming and awe-inspiring. Webb’s NIRCam (Near-Infrared Camera) captured millions of stars in these images. Older stars appear blue here, and are clustered at the galaxies’ cores. The telescope’s MIRI (Mid-Infrared Instrument) observations highlight glowing dust, showing where it exists around and between stars – appearing in shades of red and orange. Stars that haven’t yet fully formed and are encased in gas and dust appear bright red.
Webb’s high-resolution images are the first to show large, spherical shells in the gas and dust in such exquisite detail. These holes may have been created by stars that exploded and carved out giant regions in the interstellar material.
Another eye-catching detail? Several galaxy cores are awash in pink-and-red diffraction spikes. These are clear signs that these galaxies may have central active supermassive black holes or central star clusters.
These spiral galaxies are Webb’s first big batch of contributions to the Physics at High Angular resolution in Nearby GalaxieS (PHANGS) program, that includes existing images and data from the NASA/ESA Hubble Space Telescope, the Very Large Telescope’s Multi-Unit Spectroscopic Explorer (MUSE), and the Atacama Large Millimetre/submillimetre Array (ALMA). With Webb’s images, researchers can now examine these galaxies in ultraviolet, visible, infrared, and radio light.
Credit: NASA, ESA, CSA, STScI, J. Lee (STScI), T. Williams (Oxford), PHANGS Team, E. Wheatley (STScI)

If you follow each of the galaxy’s clearly defined arms, which are brimming with stars, to their centres, there may be old star clusters and – sometimes – active supermassive black holes. Only the James Webb Space Telescope can deliver highly detailed scenes of nearby galaxies in a combination of near- and mid-infrared light – and a set of these images were publicly released today.

These Webb images are part of a large, long-standing project, the Physics at High Angular resolution in Nearby GalaxieS (PHANGS) programme, which is supported by more than 150 astronomers worldwide. Before Webb took these images, PHANGS was already brimming with data from the NASA/ESA Hubble Space Telescope, the Very Large Telescope’s Multi-Unit Spectroscopic Explorer, and the Atacama Large Millimetre/submillimetre Array, including observations in ultraviolet, visible, and radio light. Webb’s near- and mid-infrared contributions have provided several new puzzle pieces.

Webb’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 haven’t 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.

To the amazement of astronomers, Webb’s images also show large, spherical shells in the gas and dust that may have been created by exploded stars.

The spiral arms’ extended regions of gas also reveal details in red and orange. Astronomers study the spacing of these features to learn how a galaxy distributes its gas and dust. These structures will provide key insights about how galaxies build, maintain, and shut off star formation.

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. The galaxy cores that are awash in pink-and-red diffraction spikes may indicate an active supermassive black hole or saturation from bright star clusters toward the centre.

There are many avenues of research that scientists can begin to pursue with the combined PHANGS data, but the unprecedented number of stars Webb resolved are a great place to begin. In addition to immediately releasing these images, the PHANGS team has also released the largest catalogue to date of roughly 100 000 star clusters.

 

Press release from ESA Webb.

Researchers using the NASA/ESA/CSA James Webb Space Telescope are getting their first look at star formation, gas, and dust in nearby galaxies with unprecedented resolution at infrared wavelengths. The data have enabled an initial collection of 21 research papers which provide new insight into how some of the smallest-scale processes in the Universe — the beginnings of star formation — impact the evolution of the largest objects in our cosmos: galaxies.

The largest survey of nearby galaxies in Webb’s first year of science operations is being carried out by the Physics at High Angular resolution in Nearby Galaxies (PHANGS) collaboration, involving more than 100 researchers from around the globe. The Webb observations are led by Janice Lee, Gemini Observatory chief scientist at the US National Science Foundation’s NOIRLab and an affiliate astronomer at the University of Arizona in Tucson.

The team is studying a diverse sample of 19 spiral galaxies, and in Webb’s first few months of science operations, observations have been made of five of those targets — M74, NGC 7496, IC 5332, NGC 1365, and NGC 1433. The results are already astounding astronomers.

The images from Webb’s Mid-Infrared Instrument (MIRI) reveal the presence of a network of highly structured features within these galaxies — glowing cavities of dust and huge cavernous bubbles of gas that line the spiral arms. In some regions of the nearby galaxies observed, this web of features appears built from both individual and overlapping shells and bubbles where young stars are releasing energy.

The high-resolution imaging needed to study these structures has long evaded astronomers — that is, until Webb came into the picture. Webb’s powerful infrared capabilities can pierce through the dust to connect the missing pieces of the puzzle. For example, specific wavelengths observable by MIRI (7.7 and 11.3 microns) are sensitive to emission from polycyclic aromatic hydrocarbons, which play a crucial role in the formation of stars and planets. These molecules were detected by Webb in the first observations by the PHANGS programme.

Studying these interactions at the finest scales can help provide insights into the larger picture of how galaxies have evolved over time.

The PHANGS team will work to create and release datasets that align Webb’s data to each of the complementary datasets obtained previously from the other observatories, to help accelerate discoveries by the broader astronomical community.

The research by the PHANGS team is being conducted as part of the General Observer program 2107. The team’s initial findings, comprising 21 individual studies, were recently published in a special focus issue of The Astrophysical Journal Letters.

Press release from ESA Webb