Circular polarisation in compact radio sources: Constraints on particle acceleration and electron-positron pairs

Abstract

It is shown that the frequency distribution of the degree of circular polarisation for a homogeneous source is sensitive to the properties of the synchrotron emitting plasma. Most of the circular polarisation comes from the region around the turn-over frequency, where the synchrotron radiation becomes optically thick. However, nearly circular characteristic waves result in circular polarisation dominated by frequencies above the turn-over frequency, while for nearly linear characteristic waves it is dominated by frequencies below. Observations argue in favour of nearly circular characteristic waves. This implies a low energy cut-off in the electron distribution substantially below that corresponding to the turn-over frequency and, simultaneously, provides an upper limit to the fraction of electron-positron pairs.

arXiv comment19 pages, 3 Appendices, Accepted to ApJ

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Cited by in corpus (5)

• Radio Observations of Magnetic Cataclysmic Variables
• Inferring AGN jet parameters using Bayesian analysis of VLBI data with non-uniform jet model
• Circular polarisation from inhomogeneous synchrotron sources
• A Multi-Mechanism Hybrid Model of Peaked-Spectrum Radio Sources
• From electrons to Janskys: Full stokes polarized radiative transfer in 3D relativistic particle-in-cell jet simulations