Astronomers used the state-of-the-art technology on the James Webb Space Telescope to study organic molecules in galactic nuclei.
Research led by Oxford University is the first of its kind to study tiny dust molecules in the nuclear region of active galaxies. The research was done using early observations from the James Webb Space Telescope (JWST). The study is the first UK-led paper to use spectroscopic data from the JWST’s Mid-Infrared Instrument (MIRI). It addresses one of the biggest challenges in modern astrophysics: understanding how galaxies form and evolve.
In the universe, polycyclic aromatic hydrocarbons (PAHs) are among the most common organic molecules. This makes them critical astronomical tools. Prebiotic compounds play a key role in life’s origin. This is because they are fundamental building blocks. Astronomers can use PAHs as sensitive barometers of the local physical conditions by tracing their emission bands in the infrared region when illuminated by stars.
James Webb Instruments
JWST’s cutting-edge instruments were used to characterize, for the first time, PAH properties in three luminous active galaxies. Ismael García-Bernete of Oxford University’s Department of Physics conducted the research. A spectroscopic study based on the MIRI of the JWST measured light in a wavelength range of 5 to 28 microns. Scientists then compared their observations to theoretical predictions. An active galaxy’s black hole is expected to destroy PAH molecules in its vicinity. The results of this study overturned that prediction. However, even in these regions where very energetic photons could potentially tear them apart, PAH molecules are actually able to survive. Furthermore, in the nuclear region, a large amount of molecular gas may protect the molecules.
Although PAH molecules survived in galaxies with supermassive black holes, the results showed these holes affected their properties significantly. This indicates the destruction of more fragile small and charged PAH molecules as the proportion of larger and neutral molecules increased. Consequently, using these PAH molecules to measure how rapidly a galaxy produces stars is severely limited.
New Insight
Researchers interested in the formation of planets and stars in distant, faint galaxies will find this research of significant interest, said Dr. García-Bernete. The next step is to analyze a larger sample of active galaxies with different properties. It is fascinating that we can observe PAH molecules in their nuclei. Consequently, scientists will be able to better understand how PAH molecules survive. Furthermore, scientists will be able to find what properties they have in nuclear regions. It is crucial to know such things so that researchers can use PAHs as an accurate tool to determine how galaxies evolve over time. This will enable them to determine how much star formation occurs. The study is published in Astronomy and Astrophysics.
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