Multi-Frequency VLBA Polarimetry and the Twin-Jet Quasar 0850+581†
Lebedev Physical Institute, Astro Space Center, Profsoyuznaya 84/32, Moscow 117997, Russia
Moscow Institute of Physics and Technology, Institutsky per., 9, Dolgoprudny 141700, Russia
Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
Author to whom correspondence should be addressed.
This paper is an extended version of our paper published in Polarised Emission from Astrophysical Jets.
Galaxies 2017, 5(4), 92; https://doi.org/10.3390/galaxies5040092
Received: 9 October 2017 / Revised: 21 November 2017 / Accepted: 28 November 2017 / Published: 30 November 2017
(This article belongs to the Special Issue Polarised Emission from Astrophysical Jets)
We present the first multi-frequency VLBA study of the quasar 0850+581 which appears to have a two-sided relativistic jet. Apparent velocity in the approaching jet changes from 3.4c to 7c with the separation from the core. The jet-to-counter-jet ratio of about 5 and apparent superluminal velocities suggest that the observing angle of the inner jet is
. It is likely that this orientation significantly changes downstream due to an interaction of the jet with the surrounding medium; signs of this are seen in polarization. A dense inhomogeneous Faraday screen is detected in the innermost regions of this quasar. We suggest that there is a presence of ionized gas in its nucleus, which might be responsible for the free-free absorption of the synchrotron emission in the jet and counter-jet at frequencies below 8.4 GHz. The experiment makes use of slowly varying instrumental polarisation factors (polarization leakage or D-terms) in time. We report application of the “D-term connection” technique for the calibration of an absolute orientation of electric vector position angle (EVPA) observed by VLBA at 4.6, 5.0, 8.1, 8.4, 15.4, 22.3, and 43.3 GHz bands during the 2007–2011.