NONTHERMAL COMPTON AND SYNCHROTRON PROCESSES IN THE JETS OF ACTIVE GALACTIC NUCLEI

We present the basic equations for calculating the time-dependent rece ived spectral flux from the optically thin emissivities produced by te mporally evolving, nonthermal electrons losing energy in a relativisti cally moving blob of plasma located at cosmological distances. Ionizat ion, bremsstrahlung, Compton, and synchrotron energy losses of the ele ctrons are considered. These equations are used to derive and calculat e the received spectral fluence produced by instantaneously injected n onthermal electrons that also scatter photons from an isotropic extern al monochromatic radiation held in the Thomson regime of scattering. T he derivation of the fluences is restricted to the regime where either synchrotron losses or Thomson losses with photons of the external rad iation field dominate the electron energy loss rate. We also derive ap proximate expressions for the synchrotron and synchrotron self-Compton fluence. Beaming factors for thin-target and thick-target models of t he electron distributions are derived. We show that ionization energy losses of relativistic electrons on the background thermal plasma of t he blob can give Comptonized gamma-ray fluence spectra with spectral b reaks Delta alpha much greater than 0.5. If only,Thomson and synchrotr on losses are important, spectral breaks much greater than 0.5 are als o possible if electrons are injected with a low-energy cutoff or if a ''snapshot'' of the spectral flux is measured over a time interval muc h less than the interval during which electrons cool. The important ob servational quantities for testing Compton-scattering models of radio galaxies and blazars are the bolometric luminosities in the radio/opti cal synchrotron component and the X-ray/gamma-ray Compton component, w hich approximately equal the peak values of the vF, spectral power flu x or fluence. Numerical simulations of jet spectra are presented, show ing the effects of different parameter values on the shapes of the syn chrotron and Compton components. We derive straightforward predictions for the simplest external Compton and synchrotron self-Compton models from the analytic expressions for the spectra. The results are applie d to quasi-simultaneous observations of 3C 279 at two different epochs , showing that this behavior can be understood if the blazar radiation results from electrons that Compton-scatter externally produced photo ns in outflowing blobs with different bulk Lorentz factors. Fits to qu asi-simultaneous observations of 3C 273 and quiescent and flaring stat es of Mrk 421 are also presented.