A broad HCO+ absorption line associated with the circumnuclear torus of
  NGC 1052
  In the circumnuclear region of the nearby radio galaxy NGC~1052. Our
$\lambda$3mm VLBI observations with the Korean VLBI Network have spatially
resolved the broad HCO$^{+}$ absorption at a velocity range of 1350--1850
km~s$^{-1}$ against a double-sided nuclear jet, and have revealed that the
HCO$^{+}$ absorption is concentrated on the receding jet and the nuclear
components. The distribution of the HCO$^{+}$ absorbing gas strongly supports
the circumnuclear torus surrounding the supermassive black hole. From the
estimations of the column density and the volume density of molecular hydrogen,
the size of the molecular gas region in the torus is at least 1~pc. The broad
spectral profile of HCO$^{+}$ is likely to be a blend of multiple gas clumps
with various velocities. The HCO$^{+}$ absorption of NGC~1052 could trace
complex kinematics in the vicinity of the active galactic nucleus, such as
inflow, outflow, turbulence, and so on.
