Evolution of X-ray Cavities in Galaxy Clusters

TL;DR

This study uses simulations and synthetic observations to analyze the evolution of X-ray cavities in galaxy clusters, revealing anisotropic size changes and emphasizing the need for detailed modeling to interpret observations accurately.

Contribution

It introduces a simulation approach that includes subgrid turbulence and synthetic X-ray observations to study cavity evolution without magnetic fields, highlighting key differences from simplified models.

Findings

Cavity size evolution is anisotropic and differs from analytical predictions.

Inferred pV energy correlates with cavity distance from cluster center.

Current models cannot distinguish hydrodynamic from magnetic effects.

Abstract

The physics of X-ray cavities in galaxy clusters is constrained by their observed morphological evolution, which depends on such poorly-understood properties as the turbulent density field and magnetic fields. Here we combine numerical simulations that include subgrid turbulence and software that produces synthetic X-ray observations to examine the evolution of X-ray cavities in the the absence of magnetic fields. Our results reveal an anisotropic size evolution that is very different from simplified, analytical predictions. These differences highlight some of the key issues that must be accurately quantified when studying AGN-driven cavities, and help to explain why the inferred pV energy in these regions appears to be correlated with their distance from the cluster center. Interpreting X-ray observations will require detailed modeling of effects including mass-entrainment, distortion by drag forces, and projection. Current limitations do not allow a discrimination between purely hydrodynamic and magnetically-dominated models for X-ray cavities.