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Abstract |
Active Galactic Nuclei (AGN) have long been regarded as prime candidates for
high-energy astrophysical neutrino emission, particularly jetted AGN, which
make up about 10% of the population. The association of a neutrino and a
neutrino flux excess with the blazar TXS 0506+056 (IceCube collab., 2018)
confirmed this expectation and revived the debate on jet particle
composition. While relativistic jets were previously thought to be
predominantly leptonic, high-energy neutrino production requires a
substantial hadronic component.
The multimessenger picture changed significantly when the most intense
neutrino excess ever observed by IceCube was linked to NGC 1068 (IceCube
collab., 2022), the archetype of non-jetted AGN. This raised the question of
how neutrinos can be produced in systems lacking relativistic emitting
regions. The most plausible site is the plasma surrounding the central
supermassive black hole, namely the accretion flow or its immediate
environment.
We therefore initiated a systematic study of the accretion properties of all
AGN associated with neutrino emission, regardless of jet presence. I will
present a new approach based on optical spectroscopic analysis and indirect
accretion emission modeling. Preliminar results point toward similar
accretion signatures for all neutrino emitting AGN, consistent with slower-
than-standard disks, though not slow enough to imply a fully different
accretion structure.
Neutrinos signalling a specific transitional accretion regime, more than
being a natural product of relativistic jets, may mark a major shift in our
understanding of AGN physics. |
