Investigating the Effects of Finite Resolution on Observed Transverse Jet Profiles

TL;DR

This paper investigates how finite observational resolution affects the detection of transverse magnetic field structures in AGN radio jets using simulated images.

Contribution

It provides empirical analysis of resolution effects on observed jet profiles, aiding in the interpretation of Faraday Rotation gradients.

Findings

Finite resolution blurs transverse jet structures.

Reliable detection requires resolution comparable to jet width.

Simulations help determine resolution thresholds for magnetic field studies.

Abstract

Both the emission properties and evolution of Active Galactic Nuclei (AGN) radio jets are dependent on the magnetic fields that thread them. Faraday Rotation gradients are a very important way of investigating these magnetic fields, and can provide information on the orientation and structure of the magnetic field in the immediate vicinity of the jet; for example, a toroidal or helical field component should give rise to a systematic gradient in the observed Faraday rotation across the jet, as well as characteristic intensity and polarization profiles. However, real observed radio images have finite resolution, usually expressed via convolution with a Gaussian beam whose size corresponds to the central lobe of the point source response function. This will tend to blur transverse structure in the jet profile, raising the question of how well resolved a jet must be in the transverse direction in order to reliably detect transverse structure associated with a helical jet magnetic field. We present results of simulated intensity, polarization and Faraday rotation images designed to directly and empirically investigate the effect of finite resolution on observed transverse jet structures.