Free Astronomy Magazine May-June 2023

MAY-JUNE 2023 N GC 1365, observed here by Webb’s Mid-Infrared Instrument (MIRI), is one of a total of 19 galaxies targeted for study by the Physics at High Angular reso- lution in Nearby Galaxies (PHANGS) collaboration. In the MIRI observations of NGC 1365, clumps of dust and gas in the interstellar medium have absorbed the light from forming stars and emitted it back out in the infrared, lighting up an intricate network of cavernous bubbles and filamentary shells created by young stars releasing energy into the galaxy’s spiral arms. [NASA, ESA, CSA, Janice Lee (NOIRLab). Image processing: Alyssa Pagan (STScI)] University of California, San Diego. 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 Tele- scope, the Atacama Large Millime- ter/Submillimeter Array, and the Very Large Telescope’s Multi Unit Spectroscopic Explorer,” added team member Adam Leroy of the Ohio State University. “But, the ear- liest 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 capabili- ties can pierce through the dust to connect the missing puzzle pieces. For example, specific wavelengths observable by MIRI (7.7 and 11.3 mi- crons) and Webb’s Near-Infrared Camera (3.3 microns) are sensitive to emission from polycyclic aro- matic hydrocarbons, which play a critical role in the formation of stars and planets. These molecules were detected by Webb in the first obser- vations by the PHANGS program. Studying these interactions at the finest scale can help provide insights into the larger picture of how galax- ies have evolved over time. “Because these observations are taken as part of what’s called a treasury program, they are available to the public as they are observed and received on Earth,” said Eva Schinnerer of the Max Planck Insti- tute for Astronomy in Heidelberg, Germany, and leader of the PHANGS collaboration. The PHANGS team will work to cre- ate and release data sets that align Webb’s data to each of the comple- mentary data sets obtained previ- ously from the other observatories, to help accelerate discovery by the broader astronomical community. “Thanks to the telescope’s resolu- tion, for the first time we can con- duct a complete census of star formation, and take inventories of the interstellar medium bubble structures in nearby galaxies beyond the Local Group,” Lee said. “ That census will help us understand how star formation and its feedback im- print themselves on the interstellar medium, then give rise to the next generation of stars, or how it actu- ally impedes the next generation of stars from being formed.” !