A sub-kpc-scale binary active galactic nucleus with double narrow-line regions

We present the kinematic properties of a type-2 Quasi stellar object (QSO), SDSS J132323.33-015941.9 at z similar to 0.35, based on the analysis of Very Large Telescope integral field spectroscopy and Hubble Space Telescope (HST) imaging, which suggest that the target is a binary active galactic nucleus (AGN) with double narrow-line regions. The QSO features double-peaked emission lines ([O III] and H beta) which can be decomposed into two kinematic components. The flux-weighted centroids of the blue and red components are separated by similar to 0.2 arcsec (0.8 kpc in projection) and coincide with the location of the two stellar cores detected in the HST broad-band images, implying that both stellar cores host an active black hole. The line-of-sight velocity of the blue component is comparable to the luminosity-weighted velocity of stars in the host galaxy, while the red component is redshifted by similar to 240 km s(-1), consistent with typical velocity offsets of two cores in a late stage of a galaxy merger. If confirmed, the target is one of the rare cases of sub-kpc-scale binary AGNs, providing a test-bed for understanding the binary AGN population.