Revisiting the complex kinematics of ionized gas at the central region
  of NGC 1068: evidence of an additional active galactic nucleus?
  We present a spatially resolved analysis of ionized gas at the nuclear region
of the nearby galaxy NGC 1068. While NGC 1068 has been known to have gas
outflows driven by its active galactic nucleus (AGN), more complex kinematical
signatures were recently reported, which were inconsistent with a rotation or
simple biconical outflows. To account for the nature of gas kinematics, we
performed a spatially resolved kinematical study, finding a morphologically
symmetric pair of approaching and receding gas blobs in the northeast region.
The midpoint of the two blobs is located at a distance of 180 pc from the
nucleus in the projected plane. The ionized gas at the midpoint shows zero
velocity and high velocity dispersion, which are characteristics of an
outflow-launching position, as the two sides of a bicone, i.e., approaching and
receding outflows are superposed on the line of sight, leading to no velocity
shift but high velocity dispersion. We investigate the potential scenario of an
additional AGN based on a multiwavelength data set. While there are other
possibilities, i.e., X-ray binary or supernova shock, the results from optical
spectropolarimetry analysis are consistent with the presence of an additional
AGN, which likely originates from a minor merger.
