Surrounding the central black hole is a luminous accretion disk. A hot corona above the accretion disk may also play a role in producing the hard X-ray continuum. The main idea, based on various observations and summarized in Fig.
More distant clouds emit narrower lines.
Blazars are then a special class of AGN which we think have their jets practically oriented towards the observer. In general, different AGN components are important at different wavelengths. The answer in the next section .