Structure of magnetic fields in intracluster cavities

TL;DR

This paper investigates the magnetic field structures within X-ray cavities in galaxy clusters, providing analytical solutions for stable configurations with implications for observed emissions and magnetic field measurements.

Contribution

It presents the first fully analytical stable solutions for magnetic field configurations in intracluster cavities, confirmed by numerical simulations.

Findings

Derived analytical stable magnetic field configurations.

Validated solutions through numerical simulations.

Produced synthetic X-ray and synchrotron emission profiles.

Abstract

Observations of clusters of galaxies show ubiquitous presence of X-ray cavities, presumably blown by the AGN jets. We consider magnetic field structures of these cavities. Stability requires that they contain both toroidal and poloidal magnetic fields, while realistic configurations should have vanishing magnetic field on the boundary. For axisymmetric configurations embedded in unmagnetized plasma, the continuity of poloidal and toroidal magnetic field components on the surface of the bubble then requires solving the elliptical Grad-Shafranov equation with both Dirichlet and Neumann boundary conditions. This leads to a double eigenvalue problem, relating the pressure gradients and the toroidal magnetic field to the radius of the bubble. We have found fully analytical stable solutions. This result is confirmed by numerical simulation. We present synthetic X-ray images and synchrotron emission profiles and evaluate the rotation measure for radiation traversing the bubble.