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

Abstract

We present the kinematic properties of a type-2 Quasi stellar object (QSO), SDSS J132323.33-015941.9 at z ~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 Hβ) which can be decomposed into two kinematic components. The flux-weighted centroids of the blue and red components are separated by ~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 ~240km 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. © 2013 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.