A special issue of “The Astrophysical Journal Letters” contains a series of articles reporting the first results of the PHANGS–JWST survey. More than one hundred researchers from the Physics at High Angular resolution in Nearby Galaxies (PHANGS) Collaboration used the James Webb Space Telescope to examine the galaxies M74, NGC 7496, IC 5332, NGC 1365, and NGC 1433. In particular, the Mid-Infrared Instrument (MIRI) made it possible to observe structures within those galaxies in previously unseen detail. The information gathered is valuable for reconstructing star formation processes and the influence they have on the gas surrounding protostars and newborn stars.
The PHANGS Collaboration is studying 19 spiral galaxies, and during the first months of the James Webb Space Telescope’s scientific mission, 5 of them were studied mainly with its MIRI instrument. The PHANGS project includes parallel investigations conducted with different instruments in various bands of the electromagnetic spectrum. Star-forming areas are difficult to study due to the amount of gas and dust that blocks many electromagnetic frequencies. Infrared emissions are among the few that pass through those interstellar clouds.
Over the course of more than thirty years, the Hubble Space Telescope has been one of the most used to pick up infrared emissions. However, many areas are dark even to Hubble and astronomers could only speculate what was going on inside them. The James Webb Space Telescope can pick up a wider range of infrared frequencies with much greater sensitivity than Hubble. Since the beginning of its scientific mission, Webb showed even better results than hoped for, and the first results of the PHANGS-JWST survey are also extraordinary.
The James Webb Space Telescope’s MIRI instrument made it possible to observe structures never seen before in the galaxies M74, NGC 7496, IC 5332, NGC 1365, and NGC 1433. Other details were captured by another Webb instrument, NIRCam (Near-Infrared Camera). Star formation is the main subject of this research and several candidate young star clusters were identified in the midst of gas and dust. Nearly 60 candidates were discovered in the galaxy NGC 7496 alone, in which Webb shows the effects of the supermassive black hole on its surroundings, which forms an active galactic nucleus.
The observed galaxies show structures of various types linked in different ways to star formation. Bight cavities of dust and large cavernous bubbles of gas around the spiral arms. In some regions of some of the observed galaxies, the web of structures appears to be built from bubble shells that are both individual and overlapping where young stars are releasing energy.
An important result was obtained at the wavelengths of 7.7 and 11.3 microns detectable by the MIRI instrument and at the wavelength of 3.3 microns detectable by the NIRCam instrument. They are sensitive to the emission of polycyclic aromatic hydrocarbons, compounds that play a crucial role in the formation of stars and planets.
All this information is very useful for creating a much more detailed census of star formation in the galaxies studied. Understanding the processes leading from gas and dust clouds to stars and planets is the ultimate goal, and this also includes understanding the influence of stellar emissions on the surrounding clouds early in their life. The James Webb Space Telescope is confirming the crucial role that was expected and those just published are only the first results of the PHANGS–JWST survey.
