Resolving Dual Active Galactic Nuclei with ~100 pc separation in MCG-03-34-64

Galaxy mergers are expected to play a key role in the evolution of galaxies and their central supermassive black holes (SMBHs). An observational signature of this phenomenon is the detection of dual active galactic nuclei (AGNs) amongst merging systems, as predicted by cosmological models of structure formation. Dual AGNs at sub-kiloparsec-scale separation are the precursors of merging black hole binaries, an important source of gravitational waves, but a paucity of such systems have been confirmed to date by direct imaging, while other similar claims have been strongly disputed. Here we report the serendipitous multiwavelength discovery of a dual black hole system with a separation of ~100 pc, in the gas-rich luminous infrared galaxy MCG-03-34-64 (z=0.016). Chandra/ACIS imaging shows two spatially-resolved peaks of equal intensity in the neutral Fe Ka emission line, consistent with a dual SMBH, which is supported by Hubble Space Telescope (HST), and Very Large Array (VLA) observations. The separation of ~100 pc is the closest dual AGN separation reported to date with spatially-resolved, multiwavelength observations.