Polycyclic aromatic hydrocarbon destruction in star-forming regions across 42 nearby galaxies

Polycyclic aromatic hydrocarbons (PAHs) are widespread in the interstellar medium (ISM) of near solar metallicity galaxies, where they play a critical role in ISM heating, cooling, and reprocessing stellar radiation. The PAH fraction, the abundance of PAHs relative to total dust mass, is a key parameter in ISM physics. Using JWST and MUSE observations of 42 galaxies from the PHANGS survey, we analyzed the PAH fraction in over 17 000 H II regions spanning a gas-phase oxygen abundance of 12 + log(O/H) = 8.0–8.8 ( Z ∼ 0.2–1.3 Z ⊙ ), and ∼400 isolated supernova remnants (SNRs). We find a significantly lower PAH fraction toward H II regions compared to a reference sample of diffuse ISM areas at matched metallicity. At 12 + log(O/H) > 8.2, the PAH fraction toward H II regions is strongly anti-correlated with the local ionization parameter, suggesting that PAH destruction is correlated with ionized gas and/or hydrogen-ionizing UV radiation. At lower metallicities, the PAH fraction declines steeply in H II regions and in the diffuse ISM, likely reflecting less efficient PAH formation in metal-poor environments. Carefully isolating dust emission from the vicinity of optically identified supernova remnants, we see evidence of selective PAH destruction from measurements of lower PAH fractions, which is, however, indistinguishable at ∼50 pc scales. Overall, our results point to ionizing radiation as the dominant agent of PAH destruction within H II regions; metallicity plays a key role in their global abundance in galaxies.

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Publication Details

Journal
Astronomy and Astrophysics
Published
2025-10-03
DOI
https://doi.org/10.1051/0004-6361/202556427
Citations
1
Primary Topic
Astrophysics and Star Formation Studies
Type
article
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1.15
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article

Polycyclic aromatic hydrocarbon destruction in star-forming regions across 42 nearby galaxies

Karin M. Sandstrom, David A. Thilker, M. Boquien, Debosmita Pathak et al.
1 citations
Astronomy and Astrophysics
Astrophysics and Star Formation Studies
1.15
article

Polycyclic aromatic hydrocarbon destruction in star-forming regions across 42 nearby galaxies

Karin M. Sandstrom, David A. Thilker, M. Boquien, Debosmita Pathak, Francesco Belfiore, Ryan Chown, Erik Rosolowsky, J. Eduardo Méndez-Delgado, Hamid Hassani, Thomas G. Williams, Jérémy Chastenet, Sumit K. Sarbadhicary, Tony D. Weinbeck, Eva Schinnerer, Enrico Congiu, Dalya Baron, Jessica Sutter, Adam K. Leroy, Hwihyun Kim, Ivan S. Gerasimov, I-Da Chiang, Leonardo Úbeda, Kathryn Kreckel, Hsi-An Pan, Daniel A. Dale, Oleg V. Egorov, Michael Huber, Hannah Koziol, Mar Canal i Saguer, Jing Li, Evgeniya Egorova, Rebecca McClain, Janice Lee
article en
1 citations

Abstract

Polycyclic aromatic hydrocarbons (PAHs) are widespread in the interstellar medium (ISM) of near solar metallicity galaxies, where they play a critical role in ISM heating, cooling, and reprocessing stellar radiation. The PAH fraction, the abundance of PAHs relative to total dust mass, is a key parameter in ISM physics. Using JWST and MUSE observations of 42 galaxies from the PHANGS survey, we analyzed the PAH fraction in over 17 000 H II regions spanning a gas-phase oxygen abundance of 12 + log(O/H) = 8.0–8.8 ( Z ∼ 0.2–1.3 Z ⊙ ), and ∼400 isolated supernova remnants (SNRs). We find a significantly lower PAH fraction toward H II regions compared to a reference sample of diffuse ISM areas at matched metallicity. At 12 + log(O/H) > 8.2, the PAH fraction toward H II regions is strongly anti-correlated with the local ionization parameter, suggesting that PAH destruction is correlated with ionized gas and/or hydrogen-ionizing UV radiation. At lower metallicities, the PAH fraction declines steeply in H II regions and in the diffuse ISM, likely reflecting less efficient PAH formation in metal-poor environments. Carefully isolating dust emission from the vicinity of optically identified supernova remnants, we see evidence of selective PAH destruction from measurements of lower PAH fractions, which is, however, indistinguishable at ∼50 pc scales. Overall, our results point to ionizing radiation as the dominant agent of PAH destruction within H II regions; metallicity plays a key role in their global abundance in galaxies.

Astronomy and AstrophysicsVol. 703
Tamkang University (TW), University of Wyoming (US), Space Telescope Science Institute (US), Institute of Astronomy and Astrophysics, Academia Sinica (TW), Whitman College (US), Johns Hopkins University (US), University of Alberta (CA), Friedrich-Alexander-Universität Erlangen-Nürnberg (DE), Université Côte d'Azur (FR), Heidelberg University (DE), Johns Hopkins Medicine (US), Arcetri Astrophysical Observatory (IT), Laboratoire AstroParticule et Cosmologie (FR), Johns Hopkins University Applied Physics Laboratory (US), Ghent University (BE), University of Oxford (GB), Universal University (RU), Kavli Institute for Particle Astrophysics and Cosmology (US), Max Planck Institute for Astronomy (DE), Gemini South Observatory (CL), Observatoire de la Côte d’Azur (FR), European Southern Observatory (CL), The Ohio State University (US), Inter-University Centre for Astronomy and Astrophysics (IN), Universidad Nacional Autónoma de México (MX), Netherlands Institute for Radio Astronomy (NL)
Openalex Percentile: Top 16%
Astrophysics and Star Formation Studies
1.15
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