The Weak Shock in the Core of the Perseus Cluster

TL;DR

This paper analyzes a weak shock in the Perseus cluster core, examining its properties and energy dissipation, and finds that additional physics may be needed to fully explain the shock structure.

Contribution

It provides detailed spectral and hydrodynamic analysis of the weak shock, highlighting discrepancies with models and suggesting interactions with filaments influence shock cooling.

Findings

No temperature jump observed across the shock

Shock energy is about 3.5 times the bubble inflation work

Shock power estimated at around 6x10^44 erg/s per bubble

Abstract

The dissipation of energy from sound waves and weak shocks is one of the most promising mechanisms for coupling AGN activity to the surrounding intracluster medium (ICM), and so offsetting cooling in cluster cores. We present a detailed analysis of the weak shock found in deep Chandra observations of the Perseus cluster core. A comparison of the spectra either side of the shock front shows that they are very similar. By performing a deprojection analysis of a sector containing the shock, we produce temperature and density profiles across the shock front. These show no evidence for a temperature jump coincident with the density jump. To understand this result, we model the shock formation using 1D hydrodynamic simulations including models with thermal conduction and gamma < 5/3 gas. These models do not agree well with the data, suggesting that further physics is needed to explain the shock structure. We suggest that an interaction between the shock and the H-alpha filaments could have a significant effect on cooling the post-shock gas. We also calculate the thermal energy liberated by the weak shock. The total energy in the shocked region is about 3.5 times the work needed to inflate the bubbles adiabatically, and the power of the shock is around 6x10^44 erg/s per bubble, just over 10^45 erg/s in total.