Magnetization of jets in luminous blazars

• Published in: Monthly notices of the Royal Astronomical Society Vol. 449; no. 1; pp. 431 - 439
• Main Authors: Janiak, M., Sikora, M., Moderski, R.
• Format: Journal Article
• Language: English
• Published: London Oxford University Press 01-05-2015
• Subjects: Astronomy; Blazars; Dominance; Dust; Flattening; Flux; Geometry; Jets; Lorentz factor; Luminosity; Magnetism; Magnetization; Mathematical analysis; Radiation; radiation mechanisms: non-thermal; quasars: general; acceleration of particles
• ISSN: 0035-8711; 1365-2966
• DOI: 10.1093/mnras/stv200

The luminosities of many powerful blazars are strongly dominated by γ-rays, which most likely result from Comptonization of radiation produced outside a jet. This observation sets certain constraints on the composition and energetics of the jet, as well as the surrounding quasar environment. We study the dependence of Compton dominance on 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 ∼0.1(θjΓ)2 for spherical geometries and ∼0.01(θjΓ)2 for planar geometries, where θj is the jet half-opening angle and Γ 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.