Proper Motion of the Sub-Parsec Scale Jet in the Radio Galaxy 3C 66B

TL;DR

This study measures the proper motion of the sub-parsec jet in galaxy 3C 66B using VLBA and Effelsburg data, revealing increasing apparent speed likely due to viewing angle changes, with possible jet acceleration.

Contribution

First detailed proper motion measurements of a sub-parsec jet in 3C 66B, suggesting relativistic beaming effects and potential jet acceleration.

Findings

Proper motion increases from 0.21 to 0.70 mas/year.

Apparent speed ranges from 0.30 c to 0.96 c.

Viewing angle changes can explain proper motion variation.

Abstract

We present proper motion of the sub-parsec scale jet in a nearby elliptical galaxy 3C 66B. Observations were made using the VLBA and partly Effelsburg 100-m telescope at 2.3 GHz and 8.4 GHz at 10 epochs over 4 years. The 8.4 GHz images showed that a proper motion increases from 0.21 to 0.70 mas/year, corresponding to an apparent speed of 0.30 c to 0.96 c, with a distance from the core on a sub-parsec scale. Our investigation suggests that the apparent increase of the proper motion can be explained by changes in the viewing angle, according to a relativistic beaming model. However, we still cannot eliminate the possibility that acceleration of the jet outflow speed or of changes of emissivity profile in the two-zone jet might be found in 3C 66B.