Properties of the intracluster medium of Abell 3667 observed with Suzaku XIS

TL;DR

This study uses Suzaku XIS observations to analyze the temperature, entropy, and shock features of the intracluster medium in Abell 3667, revealing shock heating and multi-temperature structures up to the virial radius.

Contribution

It provides detailed measurements of the temperature and entropy profiles of A3667, identifying shock features and multi-temperature structures near the radio relic region.

Findings

Temperature drops sharply at the radio relic, indicating a shock with Mach number ~2.5.

Entropy profile becomes flatter and negative near the radio relic, suggesting out-of-equilibrium plasma.

Multi-temperature structure confirmed around the relic with peaks at 1 keV and 4 keV.

Abstract

We observed the northwest region of the cluster of galaxies A3667 with the Suzaku XIS instrument. The temperature and surface brightness of the intracluster medium were measured up to the virial radius (r200-2.3 Mpc). The radial temperature profile is flatter than the average profile for other clusters until the radius reaches the northwest radio relic. The temperature drops sharply from 5 keV to about 2 keV at the northwest radio relic region. The sharp changes of the temperature can be interpreted as a shock with a Mach number of about 2.5. The entropy slope becomes flatter in the outer region and negative around the radio relic region. In this region, the relaxation timescale of electron-ion Coulomb collisions is longer than the time elapsed after the shock heating and the plasma may be out of equilibrium. Using differential emission measure (DEM) models, we also confirm the multi-temperature structure around the radio relic region, characterized by two peaks at 1 keV and 4 keV. These features suggest that the gas is heated by a shock propagating from the center to outer region.