A possible sub-kiloparsec dual AGN buried behind the galaxy curtain

• Published in: arXiv.org 2021-02
• Main Authors: Severgnini, P, Braito, V, Cicone, C, Saracco, P, Vignali, C, Serafinelli, R, R Della Ceca, Dotti, M, Cusano, F, Paris, D, Pruto, G, Zaino, A, Ballo, L, Landoni, M
• Format: Article
• Language: English
• Subjects: Active galactic nuclei; Digital imaging; Emission analysis; Galaxy mergers & collisions; Infrared imaging; Kinematics; Near infrared radiation; Photoionization; Sky surveys (astronomy); Space telescopes; Spatial resolution; Subtraction; Supermassive black holes
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.2012.09184

Although thousands of galaxy mergers are known, only a handful of sub-kiloparsec-scale supermassive black hole (SMBH) pairs have been confirmed so far, leaving a huge gap between the observed and predicted numbers of such objects. In this work, we present a detailed analysis of the Sloan Digital Sky Survey optical spectrum and of near-infrared (NIR) diffraction limited imaging of SDSS~J1431+4358. This object is a local radio-quiet type 2 active galactic nucleus (AGN) previously selected as a double AGN candidate on the basis of the double-peaked [OIII] emission line. The NIR adaptive optics-assisted observations were obtained at the Large Binocular Telescope with the LUCI+FLAO camera. We found that most of the prominent optical emission lines are characterized by a double-peaked profile, mainly produced by AGN photoionization. Our spectroscopical analysis disfavors the hypothesis that the double-peaked emission lines in the source are the signatures of outflow kinematics, leaving open the possibility that we are detecting either the rotation of a single narrow-line region or the presence of two SMBHs orbiting around a common central potential. The latter scenario is further supported by the high-spatial resolution NIR imaging: after subtracting the dominant contribution of the stellar bulge component in the host galaxy, we detect two faint nuclear sources at r