The bumps in the spectral energy distribution of active galactic nuclei

The spectral energy distribution of active galactic nuclei is investigated through calculations by composite models, which account for the coupled effect of the photoionizing flux from the active center and for shock propagation. The results show that bumps in the infrared, optical, and ultraviolet bands are produced by the emission of photoionized gas inside clouds of the narrow-line region; relatively strong radiation in the ultraviolet and X-ray domain is due to the high temperatures in the postshock region. Comparison with observational results show that a good fit can be obtained without assuming the contribution of an accretion disk, of starbursts, etc. However, the crucial role of dust in the infrared frequency range will be further investigated in a forthcoming paper.