A Kiloparsec-scale Binary Active Galactic Nucleus Confirmed by the Expanded Very Large Array

Abstract

We report the confirmation of a kiloparsec-scale binary active galactic nucleus (AGN) with high-resolution radio images from the Expanded Very Large Array (EVLA). SDSS J150243.1+111557 is a double-peaked [O III] AGN at z = 0.39 selected from the Sloan Digital Sky Survey. Our previous near-infrared adaptive optics imaging reveals two nuclei separated by 1farcs4 (7.4 kpc), and our optical integral-field spectroscopy suggests that they are a type-1-type-2 AGN pair. However, these data alone cannot rule out the single AGN scenario where the narrow emission-line region associated with the secondary is photoionized by the broad-line AGN in the primary. Our new EVLA images at 1.4, 5.0, and 8.5 GHz show two steep-spectrum compact radio sources spatially coincident with the optical nuclei. The radio power of the type-2 AGN is an order-of-magnitude in excess of star-forming galaxies with similar extinction-corrected [O II] λ3727 luminosities, indicating that the radio emission is powered by accretion. Therefore, SDSS J150243.1+111557 is one of the few confirmed kiloparsec-scale binary AGN systems. Spectral energy distribution modeling shows that SDSS J150243.1+111557 is a merger of two ~10^(11) M sun galaxies. With both black hole masses around 10^8 M_☉, the AGNs are accreting at ~10 times below the Eddington limit.