The power of blazar jets

TL;DR

This study models blazar spectral energy distributions to estimate jet power, revealing that jets are likely proton-dominated with only a small fraction of their energy emitted as radiation.

Contribution

It provides a comprehensive analysis of jet power in blazars using a simplified leptonic model, highlighting the dominance of protons over magnetic fields and leptons.

Findings

Jets radiate 2-10% of their power in high power blazars.

Jets radiate 3-30% of their power in less powerful BL Lacs.

Magnetic fields are not energetically dominant in the emission region.

Abstract

We estimate the power of relativistic, extragalactic jets by modelling the spectral energy distribution of a large number of blazars. We adopt a simple one-zone, homogeneous, leptonic synchrotron and inverse Compton model, taking into account seed photons originating both locally in the jet and externally. The blazars under study have an often dominant high energy component, which, if interpreted as due to inverse Compton radiation, limits the value of the magnetic field within the emission region. As a consequence, the corresponding Poynting flux cannot be energetically dominant. Also the bulk kinetic power in relativistic leptons is often smaller than the dissipated luminosity. This suggests that the typical jet should comprise an energetically dominant proton component. If there is one proton per relativistic electrons, jets radiate around 2-10 per cent of their power in high power blazars and 3-30 per cent in less powerful BL Lacs.