Abstract
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 ≤ 17 ∘ . 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.
Highlights
Active galactic nuclei (AGN) are among the most interesting space objects: they host supermassive black holes, creating natural laboratories with extreme physical conditions
Polarimetric Very Long Baseline Interferometric (VLBI) observations deliver a wealth of information on them and play a crucial role in the study of AGN jets
The calibration of polarimetric VLBI observations is a challenge. These require (a) a good parallactic angle coverage for suitable calibrator to determine instrumental polarization and (b) comparison of its electric vector position angle (EVPA) orientationone defined within monitoring programs to calibrate absolute orientation of the polarization angle
Summary
Active galactic nuclei (AGN) are among the most interesting space objects: they host supermassive black holes, creating natural laboratories with extreme physical conditions. The calibration of polarimetric VLBI observations is a challenge. These require (a) a good parallactic angle coverage for suitable calibrator to determine instrumental polarization and (b) comparison of its electric vector position angle (EVPA) orientationone defined within monitoring programs to calibrate absolute orientation of the polarization angle. We used small temporal variability of these values to better estimate the R-L phase offset This approach is justified for experiments with. Missed IFs or antennas still may be calibrated This approach is used to calibrate observational data of the quasar 0850+581, located at z = 1.318 and demonstrating unusual polarization properties. Study of the object was motivated by the results of opacity effect measures in 277 radio sources by [5].
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