With the James Webb Space Telescope from NASA, scientists are getting their first clear look at star formation, gas, and dust in nearby galaxies with a level of detail that has never been seen before at infrared wavelengths.
With this information, 21 research papers have been written that give new information about how some of the smallest things in our universe, like the beginnings of star formation, affect how the biggest things in our universe, like galaxies, change over time.
The Physics at High Angular resolution in Nearby Galaxies (PHANGS) collaboration, made up of more than 100 scientists from all over the world, is doing the largest survey of nearby galaxies in Webb’s first year of science operations. Janice Lee, who is the chief scientist at the National Science Foundation’s NOIRLab and an astronomer at the University of Arizona in Tucson, is in charge of the Webb observations.
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 clarity with which we are seeing the fine structure certainly caught us by surprise,” said team member David Thilker of Johns Hopkins University in Baltimore, Maryland.
“We are directly seeing how the energy from the formation of young stars affects the gas around them, and it’s just remarkable,” said team member Erik Rosolowsky of the University of Alberta, Canada.
Images from Webb’s Mid-Infrared Instrument (MIRI) show that these galaxies have a network of very well-structured parts, like glowing holes of dust and huge gas bubbles that line the spiral arms. In some parts of the nearby galaxies that have been looked at, this web of features seems to be made up of both separate and overlapping shells and bubbles where energy is being released by young stars.
“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.
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,” added team member Adam Leroy of the Ohio State University. “But the earliest stages of a star’s life cycle 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) and Webb’s Near-Infrared Camera (3.3 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.
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 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 Institute for Astronomy in Heidelberg, Germany, and leader of the PHANGS collaboration.
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 the telescope’s resolution, for the first time we can conduct 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 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 team’s initial findings, composed of 21 individual studies, were recently published in a special focus issue of The Astrophysical Journal Letters.
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