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Lookup NU author(s): Dr David RosarioORCiD
This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).
© Polycyclic aromatic hydrocarbons (PAHs) are carbon-based molecules that are ubiquitous in a variety of astrophysical objects and environments. In this work we use JWST/MIRI MRS spectroscopy of three Seyferts to compare their nuclear PAH emission with that of star-forming (SF) regions. This study represents the first of its kind to use sub-arcsecond angular resolution data of local luminous Seyferts (Lbol > 1044.46 erg s-1) with a wide wavelength coverage (4.9-28.1 μm). We present an analysis of their nuclear PAH properties by comparing the observed ratios with PAH diagnostic model grids derived from theoretical spectra. Our results show that a suite of PAH features is present in the innermost parts of luminous Seyfert galaxies (~0.45 at 12 μm; in the inner ~142-245 pc). We find that the nuclear regions of active galactic nuclei (AGN) lie at different positions of the PAH diagnostic diagrams, whereas the SF regions are concentrated around the average values of SF galaxies. In particular, we find that the nuclear PAH emission mainly originates in neutral PAHs. In contrast, PAH emission originating in the SF regions favours ionised PAH grains. The observed PAH ratios in the nuclear region of the AGN-dominated galaxy NGC 6552 indicate the presence of larger PAH molecules compared with those of the SF regions. Therefore, our results provide evidence that the AGN have a significant impact on the ionisation state (and probably the size) of the PAH grains on scales of ~142-245 pc.
Author(s): Garcia-Bernete I, Rigopoulou D, Alonso-Herrero A, Donnan FR, Roche PF, Pereira-Santaella M, Labiano A, Peralta De Arriba L, Izumi T, Ramos Almeida C, Shimizu T, Honig S, Garcia-Burillo S, Rosario DJ, Ward MJ, Bellocchi E, Hicks EKS, Fuller L, Packham C
Publication type: Article
Publication status: Published
Journal: Astronomy and Astrophysics
Year: 2022
Volume: 666
Print publication date: 01/10/2022
Acceptance date: 20/02/2022
Date deposited: 14/11/2022
ISSN (print): 0004-6361
ISSN (electronic): 1432-0746
Publisher: EDP Sciences
URL: https://doi.org/10.1051/0004-6361/202244806
DOI: 10.1051/0004-6361/202244806
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