Constraints on Supermassive Black Hole Binaries from JWST and NANOGrav

We use the recent statistics of dual active galactic nuclei (AGN) in the $JamesWebbSpaceTelescope$ (JWST) data at $z\sim 3.4$ to address two aspects of the feedback and evolution scenarios of supermassive black hole binaries (SMBHB). We find that the JWST data provide evidence for the members of a binary black hole being ‘lit’ at the same time, rather than independently – a scenario which is consistent with gas-rich mergers being responsible for concurrent AGN activity. This conclusion is supported by the recent NANOGrav Pulsar Timing Array (PTA) measurements, whose upper limits on the stochastic gravitational wave strain amplitude lie below those expected from extrapolating the dual AGN fraction. The results indicate either a ‘stalling’ of the binaries at the separations probed by NANOGrav, or rapid gas-driven inspirals.