INDUCED COMPTON-SCATTERING IN GIGAHERTZ PEAK SPECTRUM RADIO-SOURCES

We revisit the shocked shell model for the class of active galactic nu clei known as gigahertz peak spectrum (GPS) sources, incorporating new observational data on the radiation brightness temperatures. We argue that in addition to free-free absorption, induced Compton scattering will also have an important effect in forming the approximately gigahe rtz peak and in shaping the radio spectra that characterize these sour ces. Indeed, our arguments suggest that GPS sources may provide the fi rst real evidence for the role of induced Compton scattering in extrag alactic radio sources.