Deep (103 ks) \chandra\ observations of Abell 665 have revealed rich structures in this merging galaxy cluster, including a strong shock and two cold fronts. The newly discovered shock has a Mach number of M = 3.0 ± 0.6, propagating in front of a cold disrupted cloud. This makes Abell~665 the second cluster where a strong merger shock of M≈ 3 has been detected, after the Bullet cluster. The shock velocity from jump conditions is consistent with (2.7 ± 0.7) × 103 km sec−1. The new data also reveal a prominent southern cold front, with potentially heated gas ahead of it. Abell 665 also hosts a giant radio halo. There is a hint of diffuse radio emission extending to the shock at the north, which needs to be examined with better radio data. This new strong shock provides a great opportunity to study the re-acceleration model with the X-ray and radio data combined.
@article{arxiv.1603.01271,
title = {A Strong Merger Shock in Abell 665},
author = {Sarthak Dasadia and Ming Sun and Craig Sarazin and Andrea Morandi and Maxim Markevitch and Daniel Wik and Luigina Feretti and Gabriele Giovannini and Federica Govoni and Valentina Vacca},
journal= {arXiv preprint arXiv:1603.01271},
year = {2016}
}