Chandra Observation of a Weak Shock in the Galaxy Cluster A2556

Abstract

Based on a 21.5 ks \chandra\ observation of A2556, we identify an edge on the surface brightness profile (SBP) at about 160$h_{71}^{-1}$ kpc northeast of the cluster center, and it corresponds to a shock front whose Mach number $\mathcal{M}$ is calculated to be $1.25_{-0.03}^{+0.02}$. No prominent substructure, such as sub-cluster, is found in either optical or X-ray band that can be associated with the edge, suggesting that the conventional super-sonic motion mechanism may not work in this case. As an alternative solution, we propose that the nonlinear steepening of acoustic wave, which is induced by the turbulence of the ICM at the core of the cluster, can be used to explain the origin of the shock front. Although nonlinear steepening weak shock is expected to occur frequently in clusters, why it is rarely observed still remains a question that requires further investigation, including both deeper X-ray observation and extensive theoretical studies.

15 pages, 4 figures, accepted by ApJ

References in corpus (5)

• Shocks and cold fronts in galaxy clusters
• Diffuse Optical Light in Galaxy Clusters II: Correlations with Cluster Properties
• Constraints on turbulent velocity broadening for a sample of clusters, groups and elliptical galaxies using XMM-Newton
• A Chandra Study of Temperature Substructures in Intermediate-Redshift Galaxy Clusters
• Heating and Cooling in Clusters and Groups

Cited by in corpus (1)

• Standard Coupling Unification in SO(10), Hybrid Seesaw Neutrino Mass and Leptogenesis, Dark Matter, and Proton Lifetime Predictions