Twin SMBH candidates in the BCG of RBS 797

Abstract

The radio-loud BCG at the center of the cool core cluster RBS 797 is known to exhibit a misalignment of its 5 GHz radio emission observed at different VLA resolutions, with the innermost kpc-scale jets being almost orthogonal to the radio lobes which extends for tens of kpc filling the X-ray cavities seen by Chandra. The different radio directions may be caused by rapid jet reorientation due to interaction with a secondary supermassive black hole (SMBH), or to the presence of two AGN, probably in a merging phase, which are emitting radio jets in different directions. We present the results of new 5 GHz observations performed with the EVN in May 2013. In particular, we detected two compact radio components, with a projected separation of 77 pc. We discuss two possible scenarios for the origin and nature of the EVN double source, showing that both interpretations are consistent with the presence of a SMBH binary system in the BCG of RBS 797.