Speaker
Description
A large population of AGN pairs residing in the same galaxy, the so-called dual AGN, is predicted to exist at redshifts z>0.5. These systems constitute the parent population of merging black holes (BHs), making their number and properties a key ingredient for theoretical predictions of the gravitational-wave (GW) background and event rates probed by pulsar timing array (PTA) experiments and by the future Laser Interferometer Space Antenna mission (LISA).
Until recently, only a handful of dual AGN had been identified at sub-arcsecond separations. In this talk, I will present the first statistically significant sample of systems with separations ranging from 0.15″ to 0.8″ (∼kpc at z>0.5) selected using the innovative Gaia multi-peak (GMP) technique based on data from Gaia. We observed approximately one hundred systems at cosmic noon to confirm their nature and distinguish true dual AGN from gravitationally lensed systems using spatially resolved spectroscopy obtained with several ground-based AO-assisted facilities, including Keck Observatory and Very Large Telescope.
Building on the classification of these systems, I will present the first comprehensive study of dual AGN properties, including bolometric luminosities, Eddington ratios, black hole masses, mass ratios of the pairs, their fraction within the overall AGN population, and how these quantities evolve with redshift, magnitude, and separation.
For the first time, we perform a statistical comparison between a sample of ∼50 confirmed dual AGN and theoretical predictions from cosmological simulations and analytical models, including L-GALAXIES and ASTRID. These results provide the first observational constraints on the population of dual AGN at cosmic noon and enable a direct link between observations and theoretical predictions of black hole growth during galaxy mergers. In particular, the inferred distributions of dual AGN properties allow us to place new constraints on the expected rate of massive black hole mergers and to predict the population of GW events that will be detectable by LISA.