The Quest for Dual and Binary Supermassive Black Holes: A Multi-Messenger View

Understand

The quest for binary and dual supermassive black holes (SMBHs) at the dawn of the multi-messenger era is compelling.

• Detecting dual active galactic nuclei (AGN) -- active SMBHs at projected separations larger than several parsecs -- and binary AGN -- probing the scale where SMBHs are bound in a Keplerian binary -- is an observational challenge.
• The study of AGN pairs (either dual or binary) also represents an overarching theoretical problem in cosmology and astrophysics.
• The AGN triggering calls for detailed knowledge of the hydrodynamical conditions of gas in the imminent surroundings of the SMBHs and, at the same time, their duality calls for detailed knowledge on how galaxies assemble through major and minor mergers and grow fed by matter along the filaments of the cosmic web.