Electron-positron jets associated with the quasar 3C279

Wardle, J.F.C.; Homan, D.C.; Ojha, R.; Roberts, D.H.; Electron-positron jets associated with the quasar 3C279; Appeared in Nature vol. 395, pg. 457 (1998); http://pc.astro.brandeis.edu/pdfs/elec-pos.pdf;

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Abstract

A long outstanding problem in extragalactic astrophysics is the composition of the relativistic jets of plasma streaming from the nuclei of quasars and active galaxies - whether it is predominantly a "normal" (electron-proton) plasma, or a "pair" (electron-positron) plasma. Distinguishing between these possibilities is crucial for understanding the physical processes occurring close to the putative super massive black holes in galactic that create the jets. Here we present a new approach to the problem of jet composition, by detecting circularly polarized radio emission from the archtypal quasar 3C 279, using the VLBA. The circular polarization is produces by Faraday conversion, which requires that the energy distribution of the radiating particles extend to very low energies, indicating that electron-positron pairs are a major component of the jet plasma. Similar detections in three other radio sources, suggest that in general, extragalactic radio jets are composed primarily of an electron-positron plasma.