Detecting the Orbital Motion of Nearby Supermassive Black Hole Binaries with Gaia

TL;DR

This paper proposes that the Gaia space observatory can detect the orbital motion of supermassive black hole binaries in nearby active galactic nuclei within a decade, based on astrometric measurements.

Contribution

It demonstrates the potential of Gaia to identify supermassive black hole binaries through astrometric detection in the local universe.

Findings

Detectable binaries have masses around a few times 10^7 solar masses.

Detection is feasible for AGN within redshift z=0.02.

Candidate AGN are bright and nearby, with specific magnitude range.

Abstract

We show that a 10 year Gaia mission could astrometrically detect the orbital motion of ~1 sub-parsec separation supermassive black hole binary in the heart of nearby, bright active galactic nuclei (AGN). Candidate AGN lie out to a redshift of z=0.02 and in the V-band magnitude range $10 \lesssim m_V \lesssim 13$. The distribution of detectable binary masses peaks at a few times $10^7$ solar masses and is truncated above a few times $10^8$ solar masses.