Interaction of Fanaroff-Riley class II jets with a magnetised intra-cluster medium

TL;DR

This study uses 3D MHD simulations to explore how powerful jets from radio sources interact with and influence the magnetic fields in galaxy clusters, affecting observational measurements like Rotation Measure.

Contribution

It introduces a detailed model of jet-ICM interactions with magnetized plasma, revealing how jets amplify and distort magnetic fields, impacting RM observations.

Findings

Jets increase RM fluctuations and can overestimate magnetic field strength by up to 70%.

Jet orientation affects RM enhancements, more prominent in quasars.

Jets distort magnetic fields near lobes and heads, flattening RM structure functions.

Abstract

We present 3-D MHD and synthetic numerical simulations to follow the evolution of randomly magnetized intra-cluster medium plasma under the effects of powerful, light, hypersonic and bipolar jets. We prescribe the cluster magnetic field (CMF) as a Gaussian random field with power law energy spectrum tuned to the expectation for Kolmogorov turbulence. We investigate the power of jets and the viewing angle used for the synthetic Rotation Measure (RM) observations. We find the model radio sources introduce and amplify fluctuations on the RM statistical properties; the average RM and the RM standard deviation are increased by the action of the jets. This may lead to overestimations of the CMFs' strength up to 70%. The effect correlates with the jet power. Jets distort and amplify CMFs especially near the edges of the lobes and the jets' heads. Thus the RM structure functions are flattened at scales comparable to the source size. Jet-produced RM enhancements depend on the orientation of the jet axis to the line of sight and are thus more apparent in quasars than in radio galaxies.