X-Ray View of the Shock Front in the Merging Cluster Abell 3376 with Suzaku

TL;DR

This study uses Suzaku X-ray observations to identify a shock front in the merging galaxy cluster Abell 3376, revealing temperature and density changes indicative of a recent major merger and shock heating.

Contribution

First detailed Suzaku measurement of the shock front in Abell 3376, confirming the radio relic as a shock and analyzing the ICM's thermal state during merger.

Findings

Temperature drops sharply across the relic, indicating a shock with Mach number ~3.

Radial entropy profile shows deviations from simulations, suggesting ongoing relaxation.

Evidence of a recent merger shock affecting the intracluster medium.

Abstract

We report on a Suzaku measurement of the shock feature associated with the western radio relic in the merging cluster A3376. The temperature profile is characterized by an almost flat radial shape with kT ~ 4 keV within 0.5 r200 and a rise by about 1 keV inside the radio relic. Across the relic region (0.6-0.8 r200), the temperature shows a remarkable drop from about 4.7 keV to 1.3 keV. This is a clear evidence that the radio relic really corresponds to a shock front possibly caused by a past major merger. The observed sharp changes of the temperature and electron density indicate the Mach number M~3. The radial entropy profile is flatter than the prediction (r^1.1) of numerical simulations within 0.5 r200}, and becomes steeper around the relic region. These observed features and time-scale estimation consistently imply that the ICM around the radio relic has experienced a merger shock and is in the middle of the process of dynamical and thermal relaxation.