Jet and Torus Orientations in High Redshift Radio Galaxies

TL;DR

This study investigates the orientation relationship between radio jets and dusty tori in high-redshift AGN, providing observational evidence supporting the unified model and estimating jet Lorentz factors using infrared data.

Contribution

It introduces a method to determine torus inclination from infrared spectral energy distributions, confirming the perpendicularity of jets and tori in high-redshift radio galaxies.

Findings

Significant anti-correlation between core dominance and torus inclination.

Supports the unified AGN scheme with observational evidence.

Estimates jet Lorentz factor Gamma > 1.3.

Abstract

We examine the relative orientation of radio jets and dusty tori surrounding the AGN in powerful radio galaxies at z > 1. The radio core dominance R = P(20 GHz) /P(500 MHz) serves as an orientation indicator, measuring the ratio between the anisotropic Doppler-beamed core extended core emission and the isotropic lobe emission. Assuming a fixed cylindrical geometry for the hot, dusty torus, we derive its inclination i by fitting optically-thick radiative transfer models to spectral energy distributions obtained with the Spitzer Space Telescope. We find a highly significant anti-correlation (p < 0.0001) between R and i in our sample of 35 type 2 AGN combined with a sample of 18 z = 1 3CR sources containing both type 1 and 2 AGN. This analysis provides observational evidence both for the Unified scheme of AGN and for the common assumption that radio jets are in general perpendicular to the plane of the torus. The use of inclinations derived from mid-infrared photometry breaks several degeneracies which have been problematic in earlier analyses. We illustrate this by deriving the core Lorentz factor Gamma from the R-i anti-correlation, finding Gamma > 1.3.