Multi-Frequency VLBA Polarimetry and the Twin-Jet Quasar 0850+581

TL;DR

This study uses multi-frequency VLBA polarimetry to analyze the twin-jet quasar 0850+581, revealing complex jet dynamics, polarization features, and ionized gas effects, advancing understanding of jet-medium interactions.

Contribution

First multi-frequency VLBA polarimetric analysis of quasar 0850+581, identifying jet interactions, polarization structures, and ionized gas influence on emission.

Findings

Apparent jet velocity varies from 3.4c to 7c.

Jet-to-counter-jet ratio is about 5.

Presence of a dense, inhomogeneous Faraday screen and ionized gas in the nucleus.

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 $\leq33^\circ$. 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.