A high angular resolution view of the PAH emission in Seyfert galaxies using JWST/MRS data

García-Bernete, I.; Rigopoulou, D.; Alonso-Herrero, A.; Donnan, F. R.; Roche, P. F.; Pereira-Santaella, M.; Labiano, A.; Peralta de Arriba, L.; Izumi, T.; Ramos Almeida, C.; Shimizu, T.; Hönig, S.; García-Burillo, S.; Rosario, D. J.; Ward, M. J.; Bellocchi, E.; Hicks, E. K. S.; Fuller, L.; Packham, C.
Bibliographical reference

Astronomy and Astrophysics

Advertised on:
Number of authors
IAC number of authors
Refereed citations
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.
Related projects
Supermassive black holes modify the distribution of molecular gas in the central regions of galaxies. Credit: HST and C. Ramos Almeida.
Nuclear Activity in Galaxies: a 3D Perspective from the Nucleus to the Outskirts
This project consists of two main research lines. First, the study of quasar-driven outflows in luminous and nearby obscured active galactic nuclei (AGN) and the impact that they have on their massive host galaxies (AGN feedback). To do so, we have obtained Gran Telescopio CANARIAS (GTC) infrared and optical observations with the instruments
Ramos Almeida