Annu. Rev. Astron. Astrophys. 1981. 19: 373-410 Copyright © 1981 by Annual Reviews. All rights reserved

3.2 Extensions of the Spectra to Infrared-Optical and Shorter Wavelengths

The origin of the infrared, optical, and shorter continuum wavelength radiation from objects identified with compact radio sources is not well established. Nearly simultaneous radio and infrared-optical observations on a limited sample of quasars and galactic nuclei are consistent with the infrared and at least part of the optical radiation's being an extension of the radio synchrotron flux (Jones et al. 1981), but other mechanisms such as self-Compton radiation are not excluded (see, for example, O'Dell et al. 1978). Flux density measurements at submillimeter and far-infrared wavelengths will be necessary to establish the relation between the radio and infrared-optical radiation more clearly.