Non-Equilibrium Ionization State and Two-Temperature Structure in the Linked Region of Abell 399/401

TL;DR

This study uses simulations to explore non-equilibrium ionization and two-temperature structures in the linked region of galaxy clusters Abell 399/401, revealing shock layers and deviations from equilibrium affecting emission lines.

Contribution

It provides the first detailed analysis of non-equilibrium ionization and two-temperature effects in the cluster linkage region using combined N-body and SPH simulations.

Findings

Significant shock layers exist at the edge of the linked region.

Ionization state of iron departs from equilibrium at shocks and center.

K alpha line emissions are affected by non-equilibrium at shocks.

Abstract

We investigate a non-equilibrium ionization state and two-temperature structure of the intracluster medium in the linked region of Abell 399/401, using a series of N-body + SPH simulations, and find that there exist significant shock layers at the edge of the linked region, and that the ionization state of iron departs from the ionization equilibrium state at the shock layers and around the center of the linked region. As for the two-temperature structure, an obvious difference of temperature between electrons and ions is found in the edge of the linked regions. K alpha line emissions of Fe xxiv and Fe xxv are not severely affected by the deviation from the ionization equilibrium state around the center of the linked region, suggesting that the detection of relatively high metallicity in this area cannot be ascribed to the non-equilibrium ionization state of the intracluster medium. On the other hand, the K alpha emissions are significantly deviated from the equilibrium values at the shock layers, and the intensity ratio of K alpha lines between Fe xxiv-xxv and Fe xxvi is found to be significantly altered from that in the ionization equilibrium state.