CHANDRA OBSERVATION OF A WEAK SHOCK IN THE GALAXY CLUSTER A2556
- Department of Physics, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240 (China)
- Shanghai Astronomical Observatory, Chinese Academy of Sciences, 80 Nandan Road, Shanghai 200030 (China)
- National Astronomical Observatories, Chinese Academy of Sciences, 20A Datun Road, Beijing 100012 (China)
Based on a 21.5 ks Chandra observation of A2556, we identify an edge on the surface brightness profile at about 160 h {sup -1} {sub 71} kpc northeast of the cluster center, and it corresponds to a shock front whose Mach number M is calculated to be 1.25{sup +0.02} {sub -0.03}. No prominent substructure, such as sub-cluster, is found in either the optical or X-ray band that can be associated with the edge, suggesting that the conventional supersonic motion mechanism may not work in this case. As an alternative solution, we propose that the nonlinear steepening of an acoustic wave, which is induced by the turbulence of the intracluster medium 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.
- OSTI ID:
- 22167351
- Journal Information:
- Astrophysical Journal, Vol. 762, Issue 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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