2001/03/29 by Daniel C. Homan, Joanne M. Attridge, John F. C. Wardle
Physics and Astronomy · #Astrophysics and Cosmic Phenomena #Blazar #Electrical and Electromagnetic Research #Gravitational microlensing #Jupiter mass #Light curve #Planet #Polarization (electrochemistry) #Population #Solar and Space Plasma Dynamics #Stars #astro-ph
paper · pdf · doi:10.1086/321568
10 pages, 4 figures, Accepted for publication in The Astrophysical Journal (corrected typos in previous version)
arxiv created 2001/03/29 · openalex publication_date 2001/07/20 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
We present circular polarization results from a 5 GHz survey of the parsec-scale polarization properties of 40 active galactic nuclei (AGNs) made with the VLBA. We find 11 circular polarization detections at the 3 σ level or higher. This nearly quadruples the number of sources detected in circular polarization at VLBI resolution. We find no correlation between fractional linear and circular polarization across our sample. A likely explanation is external Faraday depolarization in the cores of AGNs which reduces linear polarization but leaves circular polarization unchanged. In comparing ours and other recent results to observations made ~20 years ago, we find that, in five of six cases, sources have the same sign of circular polarization today as they did 20 years ago. This suggests the presence of a long-term property of the jets, such as the polarity of a net magnetic flux, which is stable on timescales much longer than those of individual outbursts.