  Recent multimessenger studies have provided evidence for high-energy neutrino
sources that are opaque to GeV-TeV gamma rays. We present model-independent
studies on the connection between neutrinos and gamma rays in the active galaxy
NGC 1068, and find that the neutrinos most likely come from regions within
about 30-100 Schwarzschild radii. This is especially the case if neutrinos are
produced via the photomeson production process, although the constraints could
be alleviated if hadronuclear interactions are dominant. We consider the most
favorable neutrino production regions, and discuss coronae, jets, winds, and
their interactions with dense material. The results strengthen the importance
of understanding dissipation mechanisms near the coronal region and the outflow
base. There could be a connection between active galactic nuclei with
near-Eddington accretion and tidal disruptions events, in that neutrinos are
produced in the obscured vicinity of supermassive black holes.
