The PHANGS-program studies nearby 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 National Science Foundation’s NOIRLab and affiliate astronomer at the University of Arizona in Tucson.

Astounding results

The team is studying a diverse sample of 19 spiral galaxies, and in Webb’s first few months of science operations, observations of five of those targets – M74, NGC 7496, IC 5332, NGC 1365, and NGC 1433 – have taken place. 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.

“Areas which are completely dark in Hubble imaging light up in exquisite detail in these new infrared images, allowing us to study how the dust in the interstellar medium has absorbed the light from forming stars and emitted it back out in the infrared, illuminating an intricate network of gas and dust,” said team member Karin Sandstrom of the University of California, San Diego.

Star formation

Missing pieces

The high-resolution imaging needed to study these structures has long evaded astronomers – until Webb came into the picture. The PHANGS team has spent years observing these galaxies at optical, radio, and ultraviolent wavelengths using NASA’s Hubble Space Telescope, the Atacama Large Millimeter/Submillimeter Array, and the Very Large Telescope’s Multi Unit Spectroscopic Explorer, but, the earliest stages of a star’s lifecycle have remained out of view because the process is enshrouded within gas and dust clouds.

Webb’s powerful infrared capabilities can pierce through the dust to connect the missing puzzle pieces. For example, specific wavelengths observable by MIRI (7.7 and 11.3 microns) are sensitive to emission from polycyclic aromatic hydrocarbons, which play a critical role in the formation of stars and planets. These molecules were detected by Webb in the first observations by the PHANGS program.

Accelerate astronomical discoveries

Studying these interactions at the finest scale can help provide insights into the larger picture of how galaxies have evolved over time. Because these observations are taken as part of a Webb Treasury program, they are available to the public as they are observed and received on Earth.

The PHANGS team will work to create and release data sets that align Webb’s data to each of the complementary data sets obtained previously from the other observatories, to help accelerate discovery by the broader astronomical community. Thanks to Webb’s resolution, for the first time researchers can conduct a complete census of star formation, and take inventories of the interstellar medium bubble structures in nearby galaxies beyond the Local Group. That census will help researchers understand how star formation and its feedback imprint themselves on the interstellar medium, then give rise to the next generation of stars, or how it actually impedes the next generation of stars from being formed.

The dust captured by James Webb at exceptionally high sensitivity and spatial resolution in the mid-IR gives us a whole new view of how the gas is organized in galaxies. We see structures that form as the result of the energy released by young stars on small scales and also fine filamentary features on larger scales that hint at how the galaxy itself helps organize the star-forming gas," said team members Sharon Meidt van der Wel and Jérémy Chastenet. from Ghent University.

Contact

Dr. Sharon Meidt van der Wel & Dr. Jérémy Chastenet

Department of Physics and Astronomy

sharon.vanderwel@ugent.be

jeremy.chastenet@ugent.be

• Read the PHANGS team’s initial findings, comprised of 21 individual studies, in a special focus issue of The Astrophysical Journal Letters.