NGC 6240 MUSE observations

Thanks to MUSE we are able to show that the formerly unresolved southern component actually consists of two distinct nuclei separated by only 198pc. In combination with Gaia data we reach an absolute positional accuracy of only 30mas that is essential to compare optical spectra with MERLIN and VLBA radio positions. The verification and detailed study of a system with three nuclei, two of which are active and each with a mass in excess of 9x10^7^M_{sun}_, is of great importance for the understanding of hierarchical galaxy formation via merging processes since multiple mergers lead to a faster evolution of massive galaxies in comparison to binary mergers.

So far it has been suggested that the formation of galactic nuclei with multiple supermassive black holes (SMBHs) is expected to be rare in the local universe. Triple massive black hole systems might be of fundamental importance for the coalescence of massive black hole binaries in less than a Hubble time leading to the loudest sources of gravitational waves in the megahertz regime.