Almost every galaxy (with exceptions such as tidal dwarf galaxies) harbors a supermassive black hole at its center. Such a central entity affects the dynamics of stars and dust while feeding on galactic matter through accretion processes. Add the galactic magnetic field to the equation, and the result is the co-evolution of supermassive black holes and their host galaxies. However, only about 10% of known galaxies are active galaxies -- those in which the presence of a central engine in the form of a supermassive black hole causes strong non-stellar emission.
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