| 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 H α 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. |
| Authors |
Oleg V. Egorov  , Kathryn Kreckel , Karin Sandström , Adam K. Leroy , Simon C. O. Glover , Brent Groves , J. M. Diederik Kruijssen , Ashley T. Barnes , Francesco Belfiore , Frank Bigiel , Guillermo A. Blanc , M. Boquien , Yixian Cao , Jérémy Chastenet , Mélanie Chevance , Enrico Congiu , Daniel A. Dale  , Éric Emsellem , Kathryn Grasha , Ralf S. Klessen , Kirsten L. Larson , Daizhong Liu , E. J. Murphy , Hsi-An Pan , Ismael Pessa , J. Pety , Erik Rosolowsky , Fabian Scheuermann , E. Schinnerer , Jessica Sutter , David A. Thilker , Elizabeth J. Watkins , Thomas G. Williams
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