sy2
Sy2, short for Seyfert type 2 galaxy, is a class of active galactic nuclei (AGN) defined by its optical spectrum, which shows strong narrow emission lines but lacks the broad emission lines produced by fast-moving gas near the central black hole. The emission lines are primarily from the narrow-line region and include lines such as [O III] 5007, [N II], and [S II], with velocities of a few hundred kilometers per second.
The central engine of a Sy2 is a accreting supermassive black hole, similar to other Seyfert types,
In some Sy2 galaxies, a broad-line region can be detected indirectly through polarized light or infrared spectroscopy,
NGC 1068 is a canonical example. Sy2 galaxies are important for studies of AGN unification, obscuration, and