“This research is of great interest to the wider astronomy community, particularly those focused on the formation of planets and stars in the most distant and faint galaxies” said García-Bernete. This brings severe limitations to using these PAH molecules to probe how rapidly an active galaxy makes new stars. In particular, the proportion of larger and neutral molecules became greater, indicating that more fragile small and charged PAH molecules may have been destroyed. However, even where PAH molecules survived, the results showed that the supermassive black holes at the heart of galaxies had a significant impact on their properties. We were excited to find that these organic molecules can actually survive in extremely harsh conditions.” García-Bernete said: “The JWST MIRI provides us with a fantastic opportunity to observe galaxies in a way that just hasn’t been possible up until now. A potential reason could be that the molecules are protected by large amounts of molecular gas in the nuclear region. Instead, the analysis revealed that PAH molecules can actually survive in this region, even where very energetic photons could potentially rip them apart. Surprisingly, the results overturned those of previous studies that had predicted that PAH molecules would be destroyed in the vicinity of the black hole at the center of an active galaxy. The researchers then compared the observations with theoretical predictions for these molecules. The study was based on spectroscopic data from the James Webb Space Telescope’s MIRI, which specifically measures light in the 5-28 micron wavelength range. Ismael García-Bernete from Oxford University’s Department of Physics, used JWST’s cutting-edge instruments to characterize, for the first time, the PAH properties in the nuclear region of three luminous active galaxies. PAH molecules produce extremely bright emission bands in the infrared region when they are illuminated by stars, enabling astronomers to not only trace star-formation activity, but also to use them as sensitive barometers of the local physical conditions. For instance, they are considered to be fundamental building blocks of prebiotic compounds, which may have played a key role in the origin of life. Tiny dust molecules known as polycyclic aromatic hydrocarbons (PAHs) are among the most widespread organic molecules in the universe and important astronomical tools.
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