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| Title: | PHANGS-JWST First Results: Destruction of the PAH Molecules in H II Regions Probed by JWST and MUSE |
| Authors: | Egorov, Oleg V.;Kreckel, Kathryn;Sandstrom, Karin M.;Leroy, Adam K.;Glover, Simon C. O.;Groves, Brent;Kruijssen, J. M. Diederik;Barnes, Ashley. T.;Belfiore, Francesco;Bigiel, F.;Blanc, Guillermo A.;Boquien, Médéric;Cao, Yixian;Chastenet, Jérémy;Chevance, Mélanie;Congiu, Enrico;Dale, Daniel A.;Emsellem, Eric;Grasha, Kathryn;Klessen, Ralf S.;Larson, Kirsten L.;Liu, Daizhong;Murphy, Eric J.;Pan, Hsi-An;Pessa, Ismael;Pety, Jérôme;Rosolowsky, Erik;Scheuermann, Fabian;Schinnerer, Eva;Sutter, Jessica;Thilker, David A.;Watkins, Elizabeth J.;Williams, Thomas G. |
| Keywords: | Polycyclic aromatic hydrocarbons;H II regions;Interstellar dust;Astrophysics - Astrophysics of Galaxies |
| Date: | 2023-02-16 |
| Issue Date: | 2023-05-12 12:06:01 (UTC+8) |
| Publisher: | American Astronomical Society |
| 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. |
| Relation: | The Astrophysical Journal Letters 944(2) |
| DOI: | 10.3847/2041-8213/acac92 |
| Appears in Collections: | [Graduate Institute & Department of Physics] Journal Article
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