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We present the results of a deep (280 ks) Chandra observation of theOphiuchus cluster, the second-brightest galaxy cluster in the X-ray sky. Thecluster hosts a truncated cool core, with a temperature increasing from kT~1keV in the core to kT~9 keV at r~30 kpc. Beyond r~30 kpc the intra-clustermedium (ICM) appears remarkably isothermal. The core is dynamically disturbedwith multiple sloshing induced cold fronts, with indications for bothRayleigh-Taylor and Kelvin-Helmholtz instabilities. The sloshing is the resultof the strongly perturbed gravitational potential in the cluster core, with thecentral brightest cluster galaxy (BCG) being displaced southward from theglobal center of mass. The residual image reveals a likely subcluster south ofthe core at the projected distance of r~280 kpc. The cluster also harbors alikely radio phoenix, a source revived by adiabatic compression by gas motionsin the ICM. Even though the Ophiuchus cluster is strongly dynamically active,the amplitude of density fluctuations outside of the cooling core is low,indicating velocities smaller than ~100 km/s. The density fluctuations might bedamped by thermal conduction in the hot and remarkably isothermal ICM,resulting in our underestimate of gas velocities. We find a surprising, sharpsurface brightness discontinuity, that is curved away from the core, at r~120kpc to the southeast of the cluster center. We conclude that this feature ismost likely due to gas dynamics associated with a merger and not a result of anextraordinary active galactic nucleus (AGN) outburst. The cooling core lacksany observable X-ray cavities and the AGN only displays weak, point-like radioemission, lacking lobes or jets, indicating that currently it may be largelydormant. The lack of strong AGN activity may be due to the bulk of the coolingtaking place offset from the central supermassive black hole.

Deep Chandra study of the truncated cool core of the Ophiuchus cluster