Magnetization of jets in luminous blazars

TL;DR

This paper investigates how the magnetization of jets in luminous blazars influences their gamma-ray emission, finding that these jets are predominantly matter-dominated with the degree of domination depending on the geometry of external radiation regions.

Contribution

It provides a quantitative analysis of jet magnetization in luminous blazars and explores how external radiation geometry affects the jet's energetic composition.

Findings

Jets in luminous blazars are matter dominated.

Magnetization levels depend on external radiation geometry.

Jets are particularly matter dominated in flattened external radiation geometries.

Abstract

Luminosities of many powerful blazars are strongly dominated by $\gamma$-rays which most likely result from Comptonization of radiation produced outside a jet. This observation sets certain constraints on composition and energetics of the jet as well as the surrounding quasar environment. We study the dependence of a Compton dominance on a jet magnetization (the magnetic-to-matter energy flux) and on the location of the 'blazar zone'. Calculations are performed for two geometries of broad-emission-line and hot-dust regions: spherical and planar. The jet magnetization corresponding to the large observed Compton dominance is found to be $\sim 0.1 (\theta_{\rm j} \Gamma)^2$ for spherical geometries and $\sim 0.01 (\theta_{\rm j} \Gamma)^2$ for planar geometries, where $\theta_{\rm j}$ is the jet half-opening angle and $\Gamma$ is the jet Lorentz factor. This implies that jets in luminous blazars are matter dominated and that this domination is particularly strong for the flattened geometry of external radiation sources.