A Kiloparsec-Scale Binary Active Galactic Nucleus Confirmed by the
  Expanded Very Large Array
  We report the confirmation of a kpc-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 1.4" (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] 3727
luminosities, indicating that the radio emission is powered by accretion.
Therefore, SDSS J150243.1+111557 is one of the few confirmed kpc-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 Msun, the AGNs are accreting at ~10 times below the
Eddington limit.
