Letter to the Editor

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

¹ Department of Physics and Astronomy, University of California Los Angeles, 430 Portola Plaza, Los Angeles, CA 90095, USA
e-mail: ciurlo@astro.ucla.edu
² INAF-Osservatorio Astrofisico di Arcetri, largo E. Fermi 5, 50125 Firenze, Italy
³ W. M. Keck Observatory, 65-1120 Mamalahoa Highway, Kamuela, HI 96743, USA
⁴ Dipartimento di Fisica e Astronomia, Università di Firenze, Via G. Sansone 1, 50019 Sesto Fiorentino Firenze, Italy
⁵ Scuola Normale Superiore, Piazza dei Cavalieri 7, 56126 Pisa, Italy
⁶ Institute of Theoretical Astrophysics, University of Oslo, PO Box 1029 Blindern, 0315 Oslo, Norway
⁷ INAF-Osservatorio Astronomico di Padova, Vicolo Osservatorio 5, Padova, Italy
⁸ University of Ferrara, Department of Physics and Earth Sciences, Via G. Saragat, 21-44122 Ferrara, Italy
⁹ INAF-Osservatorio Astronomico di Brera, Via Brera 28, 20121 Milano, Italy
¹⁰ Instituto de Astrofísica, Facultad de Física, Pontificia Universidad Católica de Chile, Casilla 306, Santiago 22, Chile
¹¹ Physics and Astronomy Department “Augusto Righi”, Università di Bologna, Via Gobetti 93/2, 40129 Bologna, Italy
¹² INAF-Osservatorio di Astrofisica e Scienza dello Spazio di Bologna, Via Gobetti 93/3, 40129 Bologna, Italy
¹³ Institut d’Astrophysique de Paris, Sorbonne Université, CNRS, UMR 7095, 98 bis bd Arago, 75014 Paris, France

Received: 5 January 2023
Accepted: 16 February 2023

Abstract

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.