Astrochemistry

The Fraction of Dust Mass in the Form of PAHs on 10-50 pc Scales in Nearby Galaxies

By Keith Cowing

Status Report

astro-ph.GA

May 27, 2024

Filed under astro-ph.GA, astrochemistry, astronomy, biochemistry, Interstellar, JWST, organic chemistry, PAH, PHANGS-JWST, Polycyclic Aromatic Hydrocarbons, Spectroscopy

The Fraction of Dust Mass in the Form of PAHs on 10-50 pc Scales in Nearby Galaxies — R_PAH mapped in NGC 4303, with the F770W star subtraction described in Section 3.1 completed before incorperation of the F770W into the RPAH map. Yellow, pink, and blue contours show the location of the nucleus, bar, and spiral arms, respectively, as defined by the maps from Querejeta et al. (2021). Light green contours show the locations of the nebular regions from the PHANGS–MUSE nebular catalogs (Santoro et al. 2022; Groves et al. 2023). The black bar on the bottom left represents a scale of 5 kpc. Maps have been smoothed to 0. ′′9 to increase the signal to noise. — astro-ph.GA

Polycyclic aromatic hydrocarbons (PAHs) are a ubiquitous component of the interstellar medium (ISM) in z~0 massive, star-forming galaxies and play key roles in ISM energy balance, chemistry, and shielding.

Wide field of view, high resolution mid-infrared (MIR) images from JWST provides the ability to map the fraction of dust in the form of PAHs and the properties of these key dust grains at 10-50 pc resolution in galaxies outside the Local Group.

We use MIR JWST photometric observations of a sample of 19 nearby galaxies from the “Physics at High Angular Resolution in Nearby GalaxieS” (PHANGS) survey to investigate the variations of the PAH fraction. By comparison to lower resolution far-IR mapping, we show that a combination of the MIRI filters (R_PAH = [F770W+F1130W]/F2100W) traces the fraction of dust by mass in the form of PAHs (i.e., the PAH fraction, or qPAH).

Mapping R_PAH across the 19 PHANGS galaxies, we find that the PAH fraction steeply decreases in HII regions, revealing the destruction of these small grains in regions of ionized gas. Outside HII regions, we find R_PAH is constant across the PHANGS sample with an average value of 3.43±0.98, which, for an illuminating radiation field of intensity 2-5 times that of the radiation field in the solar neighborhood, corresponds to q_PAH values of 3-6%.

Jessica Sutter, Karin Sandstrom, Jérémy Chastenet, Adam K. Leroy, Eric W. Koch, Thomas G. Williams, Ryan Chown, Francesco Belfiore, Frank Bigiel, Médéric Boquien, Yixian Cao, Mélanie Chevance, Daniel A. Dale, Oleg V. Egorov, Simon C. O. Glover, Brent Groves, Ralf S. Klessen, Kathryn Kreckel, Kirsten L. Larson, Elias K. Oakes, Debosmita Pathak, Lise Ramambason, Erik Rosolowsky, Elizabeth J. Watkins

Comments: Accepted at ApJ, 39 pages, 25 figures
Subjects: Astrophysics of Galaxies (astro-ph.GA)
Cite as: arXiv:2405.15102 [astro-ph.GA] (or arXiv:2405.15102v1 [astro-ph.GA] for this version)
Submission history
From: Jessica Sutter
[v1] Thu, 23 May 2024 23:22:17 UTC (21,676 KB)
https://arxiv.org/abs/2405.15102

Astrobiology, Astrochemistry,

Keith Cowing

Explorers Club Fellow, ex-NASA Space Station Payload manager/space biologist, Away Teams, Journalist, Lapsed climber, Synaesthete, Na’Vi-Jedi-Freman-Buddhist-mix, ASL, Devon Island and Everest Base Camp veteran, (he/him) 🖖🏻

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