Published in Monthly Notices of the Royal Astronomical Society, Volume 437, Issue 1, November 10, 2013, pages 32-37.
The definitive version is available at https://doi.org/10.1093/mnras/stt1846.
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 ∼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.