Modelling the multi-wavelength emission of flat spectrum radio quasar 3C 279

TL;DR

This paper models the multi-wavelength emission of quasar 3C 279 using a length-dependent conical jet model, successfully reproducing observed spectra and pinpointing the gamma-ray emission site.

Contribution

It introduces a steady-state conical jet model that accounts for multi-wavelength emission and determines key jet parameters from observational data.

Findings

Jet length estimated at ~100 pc

Magnetic field at jet base ~0.1-1 G

Gamma-ray emission site ~0.5 pc from black hole

Abstract

We employ a length-dependent conical jet model for the jet structure and emission properties of flat spectrum radio quasar 3C 279 in the steady state. In the model, ultra-relativistic leptons are injected at the base of jet and propagate along the jet structure, non-thermal photons are produced by both synchrotron emission and inverse Comtpon scattering off synchrotron photons and external soft photons at each segment of jet. We derive the total energy spectra contribution through integrating every segment. We apply the model to the quasi-simultaneous multi-wavelength observed data of two quiescent epoches. Using the observed radio data of source, we determine the length of jet $L\sim 100$ pc, and magnetic field $B_{0}\sim 0.1-1$ G at the base of jet. Assuming a steady geometry of the jet structure and suitable physical parameters, we reproduce the multi-wavelength spectra during two quiescent observed epoches, respectively. Our results show that the initial $\gamma$-ray emission site takes place at $\sim 0.5$ pc from black hole.