Inverse Compton Process in Quasars and Seyfert-Type Nuclei

Abstract

The inverse Compton spectral power of the infrared source, which is optically thick to its own radiation due to the synchrotron self-absorption process, is calculated. A radio source of a single ensemble of relativistic electrons and magnetic fields is considered. These elec­ trons emit synchrotron radiation, the high frequency part of the high frequency cutoff of which is observed in the infrared frequency range. A small fraction of the synchrotron photons suffers the inverse Compton scattering by the same ensemble of relativistic electrons. The scattered radiation is observed in the optical range. On the basis of this interpretation, the physical parameters of the infrared and optical source of 3C 273 are determined. A pos­ sible role played by the inverse Compton process is discussed for Seyfert-type nuclei. § 1. Introduction and summary In recent years, much attention has been paid to the similarity between some of the quasars and some of the nuclei of Seyfert-type galaxies. A promi­ nent feature of these objects is the enormous energy release in the infrared frequency range. Their output energy so far observed is mainly in this frequency range. Therefore, in orde'r to clarify their structures, it is of prime importance to interpret the large infrared radiation. Though the emission mechanism of the infrared radiation of the quasars and the Seyfert-type nuclei is not yet clear, the synchrotron mechanism is one of likely candidates. The possible presence of polarization in the infrared of 3C 273/) though not confirmed, may support this mechanism. We assume the infrared radiation of quasars and Seyfert-type nuclei to be produced by the synchrotron mechanism. As for the size of infrared emitting region, the rapid time variation with the time scale of the order of one day observed for NGC 1068 and NGC