AGN jet physics and apparent opening angles

TL;DR

This paper introduces a new method to measure the product of Lorentz factor and jet opening angle in AGN jets, revealing that these jets are causally connected, which impacts models of jet physics.

Contribution

A novel approach to determine Gamma*theta_j in AGN jets using VLBI data and the AGN luminosity function, providing insights into jet causality.

Findings

Gamma*theta_j = 0.1 +- 0.03 for the MOJAVE sample

AGN jets are causally connected based on the measured parameter

Method links observed jet angles with physical jet properties

Abstract

We present a new method to measure Gamma*theta_j in flux-limited samples of active galactic nuclei (AGN) jets, where Gamma is the bulk Lorentz factor and theta_j is the jet's half-opening angle. The Gamma*theta_j parameter is physically important for models of jet launching, and also determines the effectiveness of jet instabilities and magnetic reconnection. We measure Gamma*theta_j by analyzing the observed distribution of apparent opening angles in very long baseline interferometry (VLBI) flux-limited samples of jets, given some prior knowledge of the active galactic nuclei (AGN) radio luminosity function. We then apply this method to the MOJAVE flux-limited sample of radio loud objects and find Gamma*theta_j = 0.1 +- 0.03, which implies that AGN jets are subject to a variety of physical processes that require causal connection.