Webb offers first look at star formation, gas, and dust in nearby galaxies

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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.

NGC 7496 (MIRI Image - Annotated)
This image of the nearby galaxy NGC 1433, captured by Webb’s Mid-Infrared Instrument (MIRI) shows compass arrows, scale bar, and color key for reference. The north and east compass arrows show the orientation of the image on the sky. Note that the relationship between north and east on the sky (as seen from below) is flipped relative to direction arrows on a map of the ground (as seen from above). At the lower right is a scale bar labeled 3,500 light-years, 30 arcseconds. The length of the scale bar is approximately one-fifth the total width of the image. Below the image is a color key showing which MIRI filters were used to create the image and which visible-light color is assigned to each filter. In this image of NGC 7496, blue, green, and red were assigned to Webb’s MIRI data at 7.7, 10 and 11.3, and 21 microns (the F770W, F1000W and F1130W, and F2100W filters, respectively). Scientists are getting their first look with the NASA/ESA/CSA James Webb Space Telescope’s powerful resolution at how the formation of young stars influences the evolution of nearby galaxies. The spiral arms of NGC 7496, one of a total of 19 galaxies targeted for study by the Physics at High Angular resolution in Nearby Galaxies (PHANGS) collaboration, are filled with cavernous bubbles and shells overlapping one another in this image from Webb’s Mid-Infrared Instrument (MIRI). These filaments and hollow cavities are evidence of young stars releasing energy and, in some cases, blowing out the gas and dust of the interstellar medium they plough into. Until Webb’s high resolution at infrared wavelengths came along, stars at the earliest point of their lifecycle in nearby galaxies like NGC 7496 remained obscured by gas and dust. Webb’s specific wavelength coverage (7.7 and 11.3 microns), allows for the detection of polycyclic aromatic hydrocarbons, which play a critical role in the formation of stars and planets. In Webb’s MIRI image, these are mostly found within the main dust lanes in the spiral arms. In their analysis of the new data from Webb, scientists were able to identify nearly 60 new, undiscovered embedded cluster candidates in NGC 7496. These newly identified clusters could be among the youngest stars in the entire galaxy. At the centre of NGC 7496, a barred spiral galaxy, is an active galactic nucleus (AGN). An AGN is a supermassive black hole that is emitting jets and winds. The AGN glows brightly at the centre of this Webb image. Additionally, Webb’s extreme sensitivity also picks up various background galaxies, far distant from NGC 7496, which appear green or red in some instances. NGC 7496 lies over 24 million light-years away from Earth in the constellation Grus. MIRI was contributed by ESA and NASA, with the instrument designed and built by a consortium of nationally funded European Institutes (The MIRI European Consortium) and NASA’s Jet Propulsion Laboratory, in partnership with the University of Arizona. Credit: NASA, ESA, CSA, and J. Lee (NOIRLab), A. Pagan (STScI)

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.

NGC 1365 (MIRI Image - Annotated)
This image of the nearby galaxy NGC 1433, captured by Webb’s Mid-Infrared Instrument (MIRI) shows compass arrows, scale bar, and color key for reference. The north and east compass arrows show the orientation of the image on the sky. Note that the relationship between north and east on the sky (as seen from below) is flipped relative to direction arrows on a map of the ground (as seen from above). At the lower right is a scale bar labeled 8,000 light-years, 30 arcseconds. The length of the scale bar is approximately one-fifth the total width of the image. Below the image is a color key showing which MIRI filters were used to create the image and which visible-light color is assigned to each filter. In this image of NGC 1356, blue, green, and red were assigned to Webb’s MIRI data at 7.7, 10 and 11.3, and 21 microns (the F770W, F1000W and F1130W, and F2100W filters, respectively). Scientists are getting their first look with the NASA/ESA/CSA James Webb Space Telescope’s powerful resolution at how the formation of young stars influences the evolution of nearby galaxies. NGC 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 resolution in Nearby Galaxies (PHANGS) collaboration. As revealed by 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 influenced by young stars releasing energy into the galaxy’s spiral arms. Webb’s exquisite resolution also picks up several extremely bright star clusters not far from the core and newly observed recently formed clusters along the outer edges of the spiral arms. Additionally, the Webb images provide insights into how the orbits of stars and gas vary depending on where they form, and how this results in the population of older clusters outside the inner ring of star formation. NGC 1365 is a double-barred spiral galaxy that lies about 56 million light-years away from Earth. It’s one of the largest galaxies currently known to astronomers, spanning twice the length of the Milky Way. MIRI was contributed by ESA and NASA, with the instrument designed and built by a consortium of nationally funded European Institutes (The MIRI European Consortium) and NASA’s Jet Propulsion Laboratory, in partnership with the University of Arizona. Credit: NASA, ESA, CSA, and J. Lee (NOIRLab), A. Pagan (STScI)

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.

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