2016ApJ...826...91A

We analyzed deep Chandra ACIS-I exposures of the cluster-scale X-ray halo surrounding the radio source 4C+37.11. This remarkable system hosts the closest resolved pair of super-massive black holes and an exceptionally luminous elliptical galaxy, the likely product of a series of past mergers. We characterize the halo with r₅₀₀ ∼ 0.95 Mpc, M₅₀₀=2.5±0.2 x 10¹⁴ M_☉, kT=4.6±0.2 keV, and a gas mass of M_g,500=2.2±0.1 x 10¹³ M_☉. The gas mass fraction within r₅₀₀ is f_g=0.09±0.01. The entropy profile shows large non-gravitational heating in the central regions. We see several surface brightness jumps, associated with substantial temperature and density changes but approximate pressure equilibrium, implying that these are sloshing structures driven by a recent merger. A residual intensity image shows a core spiral structure closely matching that seen in the Perseus cluster, although at z=0.055 the spiral pattern is less distinct. We infer that the most recent merger occurred 1-2 Gyr ago and that the event that brought the two observed super-massive black holes to the system core is even older. Under this interpretation, the black hole binary pair has, unusually, remained at a parsec-scale separation for more than 2 Gyr.