X-ray detection of the proto supermassive binary black hole at the centre of Abell 400

Context. We report the first X-ray detection of a proto supermassive binary black hole at the centre of Abell 400. Using the Chandra Advanced CCD Imaging Spectrometer , we are able to clearly resolve the two active galactic nuclei in 3C 75, the well known double radio source at the centre of Abell 400. Aims. Through analysis of the new Chandra observation of Abell 400 along with 4.5 GHz and 329 MHz Very Large Array radio data, we will show new evidence that the active galactic nuclei in 3C 75 are a bound system. Methods. Using the high quality X-ray data, we map the temperature, pressure, density and entropy of the inner regions as well as the cluster profile properties out to ${\sim}18\arcmin$. We compare features in the X-ray and radio images to determine the interaction between the intracluster medium and extended radio emission. Results. The Chandra image shows an elongation of the cluster gas along the northeast-southwest axis; aligned with the initial bending of 3C 75's jets. Additionally, the temperature profile shows no cooling core, consistent with a merging system. There is an apparent shock to the south of the core consistent with a Mach number of ${\cal M}\sim1.4$ or speed of $v\sim1200$ km s -1 . Both active galactic nuclei, at least in projection, are located in the low entropy, high density core just north of the shock region. We find that the projected path of the jets does not follow the intra-cluster medium surface brightness gradient as expected if their path were due to buoyancy. We also find that both central active galactic nuclei are extended and include a thermal component. Conclusions. Based on this analysis, we conclude that the active galactic nuclei in 3C 75 are a bound system from a previous merger. They are contained in a low entropy core moving through the intracluster medium at 1200 km s -1 . The bending of the jets is due to the local intracluster medium wind.