The Observed Polarization Direction Depending on Geometrical and Kinematic Parameters of Relativistic Jets

Abstract

The study of the polarization direction is crucial in the issue of restoring the spatial structure of the magnetic field in the active galaxy parsec-scale jets. But, due to relativistic effects, the magnetic field projected onto the celestial sphere in the source reference frame cannot be assumed to be orthogonal to the observed direction of the electric vector in the wave. Moreover, the local axis of the jet component may not coincide with its motion direction, which affects the observed polarization direction. In this article, we analyze the transverse to jet distributions of the electric vector in the wave, obtained as a result of modeling with different jet kinematic and geometrical parameters for a helical magnetic field with a different twist angle and for a toroidal magnetic field in the center, surrounded by a varying thickness sheath, penetrated by a poloidal field. We obtained: (1) the shape of the electric vector transverse distribution depends in a complex way on the angles of the jet axis and the velocity vector with the line of sight; (2) ambiguity in determining the twist direction of the helical magnetic field under using only the distributions of the electric vector in the wave; (3) both considered magnetic field topologies can reproduce both the “spine–sheath” polarization structure and individual bright features with the longitudinal to the jet axis polarization direction.

Appendices

APPENDIX A

EV DISTRIBUTIONS FOR DIFFERENT MODEL PARAMETERS

Figure captions 5–17 for the article of Butuzova. Appendix A.

Fig. 5.

Shapes of EV distributions depending on the angle of the velocity vector ($\theta$) and the jet component axis (${{\theta }_{\rho }}$) to the line of sight for $\psi {\kern 1pt} ' = 0^\circ$. Solid, dashed, and dotted lines are associated with intervals of high, medium, and small values, respectively. The intervals of $\theta$ are indicated at the top of each plot.

Fig. 6.

The same as in Fig. 5, for $\psi {\kern 1pt} ' = 10^\circ$.

Fig. 7.

The same as in Fig. 5, for $\psi {\kern 1pt} ' = 25^\circ$.

Fig. 8.

The same as in Fig. 5, for $\psi {\kern 1pt} ' = 45^\circ$.

Fig. 9.

The same as in Fig. 5, for $\psi {\kern 1pt} ' = 55^\circ$.

Fig. 10.

The same as in Fig. 5, for $\psi {\kern 1pt} ' = 65^\circ$.

Fig. 11.

The same as in Fig. 5, for $\psi {\kern 1pt} ' = 75^\circ$.

Fig. 12.

The same as in Fig. 5, for $\psi {\kern 1pt} ' = 90^\circ$.

Fig. 13.

The shapes of the EV distributions depend on the angle of the velocity vector ($\theta$) and jet component axis (${{\theta }_{\rho }}$) to the line of sight for ${{R}_{t}} = 0.25$. Solid, dashed, and dotted lines are associated with intervals of high, medium and small values of $\theta$, respectively. The intervals of $\theta$ are indicated at the top of each plot.

Fig. 14.

The same as in Fig. 13, for ${{R}_{t}} = 0.33$.

Fig. 15.

The same as in Fig. 13, for ${{R}_{t}} = 0.5$.

Fig. 16.

The same as in Fig. 13, for ${{R}_{t}} = 0.7$.

Fig. 17.

The same as in Fig. 13, for ${{R}_{t}} = 0.9$.

APPENDIX B

COMBINATIONS OF EV DISTRIBUTION SHAPES IN AN INDIVIDUAL JET

Figure captions 18–30 for the article of Butuzova. Appendix B.

Fig. 18.

Combination of EV distribution shapes in each model jet for $\psi {\kern 1pt} ' = 0^\circ$. Those that additionally contain type 7 are marked in black.

Fig. 19.

The same as in Fig. 18, for $\psi {\kern 1pt} ' = 10^\circ$.

Fig. 20.

The same as in Fig. 18, for $\psi {\kern 1pt} ' = 25^\circ$.

Fig. 21.

The same as in Fig. 18, for $\psi {\kern 1pt} ' = 45^\circ$.

Fig. 22.

The same as in Fig. 18, for $\psi {\kern 1pt} ' = 55^\circ$.

Fig. 23.

The same as in Fig. 18, for $\psi {\kern 1pt} ' = 65^\circ$.

Fig. 24.

The same as in Fig. 18, for $\psi {\kern 1pt} ' = 75^\circ$.

Fig. 25.

The same as in Fig. 18, for $\psi {\kern 1pt} ' = 90^\circ$.

Fig. 26.

Combination of EV distribution shapes in each model jet for ${{R}_{t}} = 0.25$. Those that additionally contain type 7 are marked in black.

Fig. 27.

The same as in Fig. 26, for ${{R}_{t}} = 0.33$.

Fig. 28.

The same as in Fig. 26, for ${{R}_{t}} = 0.5$.

Fig. 29.

The same as in Fig. 26, for ${{R}_{t}} = 0.7$.

Fig. 30.

The same as in Fig. 26, for ${{R}_{t}} = 0.9$.