Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: 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.

21
The categories of this paper are: adap-org
19
The categories of this paper are: eess
8
The categories of this paper are: hep-ex
15
The categories of this paper are: nucl-ex
29
The categories of this paper are: funct-an
37
The categories of this paper are: supr-con
12
The categories of this paper are: nucl-th
27
The categories of this paper are: comp-gas
25
The categories of this paper are: patt-sol
16
The categories of this paper are: stat
36
The categories of this paper are: cmp-lg
28
The categories of this paper are: alg-geom
20
The categories of this paper are: acc-phys
1
The categories of this paper are: cs
26
The categories of this paper are: bayes-an
32
The categories of this paper are: atom-ph