ALMA 0.02"-resolution observations reveal HCN-abundance-enhanced
  counter-rotating and outflowing dense molecular gas at the NGC 1068 nucleus
  We present ALMA ~0.02"-resolution observations of the nucleus of the nearby
(~14 Mpc) type-2 AGN NGC 1068 at HCN/HCO+/HNC J=3-2 lines, as well as at their
13C isotopologue and vibrationally excited lines, to scrutinize the
morphological/dynamical/chemical/physical properties of dense molecular gas in
the putative dusty molecular torus around a mass-accreting supermassive black
hole. We confirm almost east-west-oriented dense molecular gas emission both
morphologically and dynamically, which we regard as coming from the torus.
Bright emission is compact (<3 pc), and low-surface-brightness emission extends
out to 5-7 pc. These dense molecular gas properties are not symmetric between
the eastern and western torus. The HCN J=3-2 emission is stronger than the HCO+
J=3-2 emission within the ~7 pc torus region, with an estimated dense molecular
mass of (0.4-1.0)x10^6Msun. We interpret that HCN abundance is enhanced in the
torus. We detect signatures of outflowing dense molecular gas and a
vibrationally excited HCN J=3-2 line. Finally, we find that in the innermost
(<1 pc) part of the torus, the dense molecular line rotation velocity, relative
to the systemic velocity, is the opposite of that in the outer (>2 pc) part, in
both the eastern and western torus. We prefer a scenario of counter-rotating
dense molecular gas with innermost almost-Keplerian-rotation and outer slowly
rotating (far below Keplerian) components. Our high-spatial-resolution dense
molecular line data reveal that torus properties of NGC 1068 are much more
complicated than the simple axi-symmetrically rotating torus picture in the
classical AGN unification paradigm.
