Excitation and Destruction of Small Polycyclic Aromatic Hydrocarbons by the Luminous Seyfert Nucleus of NGC 4151
Abstract
We present a spatially-resolved detection of 3.3 μm emission from polycyclic aromatic hydrocarbons (PAHs) within the circumnuclear ∼200 pc of the archetypal Seyfert galaxy NGC 4151, using new JWST NIRSpec/IFU spectroscopy. PAHs are detected down to the innermost 50 pc, though it is likely that PAHs also exist at smaller radii, as PAH detections closer than this seem to be limited by continuum dilution. This is contrary to expectations that PAH grains, especially the smallest grains that carry the 3.3 μm feature, could not survive near an active galactic nucleus (AGN). Furthermore, the surface brightness of PAH emission increases as radius from the nucleus decreases. We interpret this as evidence that the AGN supplies energy for PAH excitation by driving ultraviolet emission in nearby H and H2 gas. We do not detect PAH emission within the narrow line region (NLR) that hosts highly ionized and outflowing gas, suggesting that the AGN may also destroy PAHs in these regions, depending on geometry. Together, these results show that an AGN has a complex, multifaceted role in the life cycle of PAHs and in PAH excitation.
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BibTeX
@misc{donnelly2026excitation,
title = {{Excitation and Destruction of Small Polycyclic Aromatic Hydrocarbons by the Luminous Seyfert Nucleus of NGC 4151}},
author = {Grant P. Donnelly and J. -D. T. Smith and Sebastian F. Hönig and Daniel A. Dale and Tanio Díaz-Santos and B. T. Draine and Brandon S. Hensley and Thomas S. -Y. Lai and Karin M. Sandstrom and Andrey Vayner},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.36651},
eprint = {2610.36651},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.36651},
note = {CC BY-NC-SA 4.0},
}
RIS
TY - UNPB
TI - Excitation and Destruction of Small Polycyclic Aromatic Hydrocarbons by the Luminous Seyfert Nucleus of NGC 4151
AU - Grant P. Donnelly
AU - J. -D. T. Smith
AU - Sebastian F. Hönig
AU - Daniel A. Dale
AU - Tanio Díaz-Santos
AU - B. T. Draine
AU - Brandon S. Hensley
AU - Thomas S. -Y. Lai
AU - Karin M. Sandstrom
AU - Andrey Vayner
PY - 2026
DA - 2026/10/27
PB - arXiv
DO - 10.48550/arxiv.2610.36651
UR - https://arxiv.org/abs/2610.36651
AB - We present a spatially-resolved detection of 3.3 μm emission from polycyclic aromatic hydrocarbons (PAHs) within the circumnuclear ∼200 pc of the archetypal Seyfert galaxy NGC 4151, using new JWST NIRSpec/IFU spectroscopy. PAHs are detected down to the innermost 50 pc, though it is likely that PAHs also exist at smaller radii, as PAH detections closer than this seem to be limited by continuum dilution. This is contrary to expectations that PAH grains, especially the smallest grains that carry the 3.3 μm feature, could not survive near an active galactic nucleus (AGN). Furthermore, the surface brightness of PAH emission increases as radius from the nucleus decreases. We interpret this as evidence that the AGN supplies energy for PAH excitation by driving ultraviolet emission in nearby H and H_2 gas. We do not detect PAH emission within the narrow line region (NLR) that hosts highly ionized and outflowing gas, suggesting that the AGN may also destroy PAHs in these regions, depending on geometry. Together, these results show that an AGN has a complex, multifaceted role in the life cycle of PAHs and in PAH excitation.
ER -