2023ApJ...952...45B

Triple-active galactic nucleus (AGN) systems are expected to be the result of the hierarchical model of galaxy formation. Since there are very few of them confirmed as such, we present the results of a new study of the triple AGN candidate SDSS J102700.40+174900.8 (center nucleus) through observations with the GTC-MEGARA Integral Field Unit. 1D and 2D analysis of the line ratios of the three nuclei allow us to locate them in the EW(Hα) versus [N II]/Hα diagram. The central nucleus is found to be a retired galaxy (or fake AGN). The neighbors are found to be a strong AGN (southeastern nucleus, J102700.55+174900.2), compatible with a Seyfert 2 (Sy2) galaxy, and a weak AGN (northern nucleus, J102700.38+174902.6), compatible with a LINER2. We find evidence that the neighbors constitute a dual AGN system (Sy2-LINER2) with a projected separation of 3.98 kpc in the optical bands. The Hα velocity map shows that the northern nucleus has an Hα emission with a velocity offset of ∼-500 km s^–1, whereas the southeastern nucleus has a rotating disk and Hα extended emission at kiloparsec scales. Chandra archival data confirm that the neighbors have X-ray (0.5-2) keV and (2-7) keV emission, whereas the center nucleus shows no X-ray emission. A collisional ring with knots is observed in Hubble Space Telescope images of the southeastern nucleus. These knots coincide with star formation regions that, along with the ring, are predicted in a head-on collision. In this case, the morphology changes are probably due to a minor merger that was produced by the passing of the northern through the southeastern nucleus.