Searching for pairs of actively accreting supermassive black holes in the Gaia FPR GravLens catalog

Abstract

Observational data on dual supermassive black holes (SMBHs) are scarce, even though they should be common according to the current hierarchical formation model for galaxies. We present hereby a method to detect such dual systems, involving an already known quasar, as two luminosity peaks with angular separations smaller than one arcsecond (1″). It is based on the analysis of the spatial distribution of the Gaia data delivered in the Focused Product Release (FPR), that published for the first time detections made by Gaia at the epoch level. This approach relies on the selection of elongated spatial distributions of epoch measurements, due to two clumps of detections, checked against images coming from the PanSTARRS1 and 2MASS surveys. We have analyzed the 3.8 million of quasars flagged as single in the Gaia FPR extra-galactic table and we currently end up with only 8 dual AGN candidates, applying very conservative thresholds. G-band magnitude of each of the two luminosity peaks is provided for these candidates. The mean value of the angular separation between these two components is found to be equal to 0.3″. This demonstrates the ability of Gaia epoch data to detect previously unknown dual sources, which might be compact dual AGN.