Abstract
Abstract
Polycyclic aromatic hydrocarbons (PAHs) play a critical role in the reprocessing of stellar radiation and balancing the heating and cooling processes in the interstellar medium but appear to be destroyed in H ii regions. However, the mechanisms driving their destruction are still not completely understood. Using PHANGS–JWST and PHANGS–MUSE observations, we investigate how the PAH fraction changes in about 1500 H ii regions across four nearby star-forming galaxies (NGC 628, NGC 1365, NGC 7496, and IC 5332). We find a strong anticorrelation between the PAH fraction and the ionization parameter (the ratio between the ionizing photon flux and the hydrogen density) of H ii regions. This relation becomes steeper for more luminous H ii regions. The metallicity of H ii regions has only a minor impact on these results in our galaxy sample. We find that the PAH fraction decreases with the Hα equivalent width—a proxy for the age of the H ii regions—although this trend is much weaker than the one identified using the ionization parameter. Our results are consistent with a scenario where hydrogen-ionizing UV radiation is the dominant source of PAH destruction in star-forming regions.
Funder
Deutsche Forschungsgemeinschaft
EC ∣ European Research Council
ANID ∣ Fondo Nacional de Desarrollo Científico y Tecnológico
Gouvernement du Canada ∣ Natural Sciences and Engineering Research Council of Canada
National Science Foundation
CNRS ∣ Institut national des sciences de l’Univers
National Science and Technology Council of Taiwan
ANID Basal
ERC
German Excellence Strategy
German Ministry for Economic Affairs
Australian Research Council Centre of Excellence
Australian Research Council
Publisher
American Astronomical Society
Subject
Space and Planetary Science,Astronomy and Astrophysics
Cited by
15 articles.
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