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Access through your institution Buy or subscribe Polycyclic aromatic hydrocarbons (PAHs) are large molecules formed of tens, if not hundreds, of carbon atoms, along with hydrogen and
potentially other elements such as nitrogen. They are the results of complex chemical processes. In the interstellar medium, PAHs absorb starlight, and re-radiate it in the infrared, making
PAHs visible to telescopes like JWST. Justin Spilker and colleagues have reported the detection of an infrared PAH emission feature from a strongly lensed galaxy similar in mass to our own
at a redshift _z_ = 4.2, when the Universe was less than 1.5 billion years old. This is only the second known galaxy with PAH emission at _z_ ~ 4. The detection came as part of the TEMPLATES
Early Release Science programme, which is dedicated to studying lensed galaxies. JWST’s MIRI instrument, operating in medium-resolution spectroscopy mode, observed the redshifted 3.3 μm PAH
feature from galaxy SPT-S J041839-4751.9 with the aid of a foreground galactic lens at _z_ ~ 0.3. The large equivalent width of the 3.3 μm feature indicates that it originates in a
star-forming environment, rather than in the hot environment close to the galaxy’s putative active galactic nucleus. Spatial variations in the feature and its underlying continuum are seen,
suggesting either that PAHs are segregated or the illuminating UV field is inhomogeneous. The infrared luminosity of the galaxy is equivalent to a star-formation rate of 350 ± 60 _M_☉ yr–1,
which is sufficiently high to drive an outflow of cold molecular gas. This is a preview of subscription content, access via your institution ACCESS OPTIONS Access through your institution
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AUTHOR INFORMATION AUTHORS AND AFFILIATIONS * Nature Astronomy https://www.nature.com/natastron/ Paul Woods Authors * Paul Woods View author publications You can also search for this author
inPubMed Google Scholar CORRESPONDING AUTHOR Correspondence to Paul Woods. RIGHTS AND PERMISSIONS Reprints and permissions ABOUT THIS ARTICLE CITE THIS ARTICLE Woods, P. Complex molecules in
an early galaxy. _Nat Astron_ 7, 641 (2023). https://doi.org/10.1038/s41550-023-02021-w Download citation * Published: 16 June 2023 * Issue Date: June 2023 * DOI:
https://doi.org/10.1038/s41550-023-02021-w SHARE THIS ARTICLE Anyone you share the following link with will be able to read this content: Get shareable link Sorry, a shareable link is not
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