Long Term Evolution of Magnetized Bubbles in Galaxy Clusters

TL;DR

This study uses magnetohydrodynamic simulations to show that magnetized bubbles from radio galaxies can survive for billions of years in galaxy clusters, explaining observed ghost cavities and filament structures.

Contribution

The paper demonstrates the long-term stability of magnetized bubbles in galaxy clusters through detailed simulations, highlighting magnetic fields' role in their longevity.

Findings

Approximately 3.5% of initial magnetic energy remains after 8 billion years.

Magnetic fields stabilize bubbles against Rayleigh-Taylor and Kelvin-Helmholtz instabilities.

A 500 kpc filament with ~0.88 μG magnetic field forms along bubble paths.

Abstract

We have performed nonlinear ideal magnetohydrodynamic simulations of the long term evolution of a magnetized low-density "bubble" plasma formed by a radio galaxy in a stratified cluster medium. It is found that about 3.5% of the initial magnetic energy remains in the bubble after $\sim 8 \times 10^{9}$ years, and the initial magnetic bubble expansion is adiabatic. The bubble can survive for at least $8 \times 10^9$ years due to the stabilizing effect of the bubble magnetic field on Rayleigh-Taylor and Kelvin-Holmholtz instabilities, possibly accounting for "ghost cavities" as observed in Perseus-A\@. A filament structure spanning about 500 kpc is formed along the path of bubble motion. The mean value of the magnetic field inside this structure is $\sim 0.88$ $\mu$G at $\sim8\times10^9$ years. Finally, the initial bubble momentum and rotation have limited influence on the long term evolution of the bubble.