Intrinsic Physical Conditions and Structure of Relativistic Jets in Active Galactic Nuclei

TL;DR

This paper analyzes the physical conditions of relativistic jets in active galactic nuclei using core shift observations, estimating key plasma parameters, and explaining jet structure and acceleration within an MHD framework.

Contribution

It provides new estimates of plasma density and magnetization in AGN jets, linking observational data with MHD models to explain jet structure and dynamics.

Findings

Median multiplicity parameter is 3x10^13.

Median magnetization parameter is 8.

Magnetic field and particle density are higher at jet centers.

Abstract

The analysis of the frequency dependence of the observed shift of the cores of relativistic jets in active galactic nuclei (AGN) allows us to evaluate the number density of the outflowing plasma n and, hence, the multiplicity parameter, which is a ratio of particle number density to Goldreich-Julian number density. We have obtained the median value for the multiplicity parameter to be 3x10^13 and the median value for the Michel magnetization parameter is 8 from an analysis of 97 sources. Since the magnetization parameter can be interpreted as the maximum possible Lorentz factor of the bulk motion which can be obtained for relativistic magnetohydrodynamic (MHD) flow, this estimate is in agreement with the observed superluminal motion of bright features in AGN jets. Moreover, knowing these key parameters, one can determine the transverse structure of the flow. We show that the poloidal magnetic field and particle number density are much larger in the center of the jet than near the at boundary. The MHD model can also explain the typical observed level of jet acceleration. Finally, casual connectivity of strongly collimated jets is discussed.