New multiple AGN systems with subarcsec separation: Confirmation of candidates selected via the novel GMP method

The existence of multiple active galactic nuclei (AGNs) at small projected distances on the sky is due to either the presence of multiple, inspiraling supermassive black holes, or to gravitational lensing of a single AGN. Both phenomena allow us to address important astrophysical and cosmological questions. However, few kiloparsec-separation multiple AGNs are currently known. Recently, the newly developed Gaia multi-peak (GMP) method provided numerous new candidate members of these populations. We present spatially resolved, integral-field spectroscopy of a sample of four GMP-selected multiple AGN candidates. In all of these systems, we detect two or more components with subarcsec separations. We find that two of the systems are dual AGNs, one is either an intrinsic triple or a lensed dual AGN, while the last system is a chance alignment of an AGN and a star. Our observations double the number of confirmed multiple AGNs at projected separations below 7 kpc at z > 0.5, present the first detection of a possible triple AGN in a single galaxy at z > 0.5, and successfully test the GMP method as a novel technique to discover previously unknown multiple AGNs.

Automated summary

The existence of multiple AGNs at small projected distances on the sky is important for addressing astrophysical and cosmological questions. The newly developed Gaia multi-peak method has provided numerous new candidate members of these populations. Spatially resolved spectroscopy confirms the presence of multiple AGNs in four GMP-selected candidates, doubling the number of confirmed multiple AGNs at projected separations below 7 kpc at z > 0.5 and presenting the first detection of a possible triple AGN.