Astrochemistry

A Study of Polycyclic Aromatic Hydrocarbon Emission in 30 Dor as seen by JWST

By Keith Cowing
Status Report
astro-ph.GA
October 29, 2024
Filed under , , , , , , , , , , , , , , ,
A Study of Polycyclic Aromatic Hydrocarbon Emission in 30 Dor as seen by JWST
JWST/NIRCam F335M image of 30 Dor. The blue box represents the field of view of the MIRI/MRS Channel 1. The inset shows the spectroscopic FOVs: NIRSpec (green), MIRI/MRS Channel 1 (blue), MIRI/MRS Channel 2 (pink), and MIRI/MRS Channel 3 (yellow). — astro-ph.GA

Polycyclic aromatic hydrocarbons (PAHs) are responsible for strong mid-IR emission features near star-forming regions. It is well known that low-metallicity environments exhibit weaker PAH emission, but it is not clear how the metallicity affects the properties of the emitting PAH population.

We present a detailed study of the PAH emission in the low-metallicity regime represented by 30 Dor in the Large Magellanic Cloud (LMC) and we compare it to the PAH emission in the Orion Bar to investigate the characteristics of the PAH population and how the environments affects the resulting IR emission. We analyze JWST observations of 30 Dor that include imaging (NIRCam, MIRI) and spectroscopy (NIRSpec/IFU, MIRI/MRS).

We extracted NIRSpec/IFU and MIRI/MRS spectra from 18 apertures that cover the morphological structures of 30 Dor. We characterize the profiles and relative intensities of PAH emission in these apertures. The detailed profiles of the PAH emission bands in 30 Dor are all very similar, and compare well to those from one of the dissociation fronts (DF2) in the Orion Bar. The relative band ratios on the other hand show a much larger range than in the Orion Bar.

The PAH emission in 30 Dor originates from a population with a higher ionization fraction than in the Orion Bar, and a size distribution that has more smaller PAHs. Since smaller PAHs typically photo-fragment before larger PAHs, our findings support the hypothesis that the lower PAH emission for lower metallicities is the result of inhibition of growth toward larger PAHs rather than photo-fragmentation.

Congcong Zhang, Joelene Hales, Els Peeters, Jan Cami, Ameek Sidhu, Junfeng Zhen

Subjects: Astrophysics of Galaxies (astro-ph.GA)
Cite as: arXiv:2410.18909 [astro-ph.GA] (or arXiv:2410.18909v1 [astro-ph.GA] for this version)
https://doi.org/10.48550/arXiv.2410.18909
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Submission history
From: Congcong Zhang
[v1] Thu, 24 Oct 2024 16:59:41 UTC (22,386 KB)
https://arxiv.org/abs/2410.18909
Astrobiology, Astrochemistry,

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) 🖖🏻