Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Molecular absorption in Cen A on VLBI scales   Centaurus A, the nearest AGN shows molecular absorption in the millimeter and
radio regime. By observing the absorption with VLBI, we try to constrain the
distribution of the gas, in particular whether it resides in the circumnuclear
region. Analysis of VLBA observations in four OH and two H2CO transitions is
presented here, as well as molecular excitation models parameterized with
distance from the AGN. We conclude that the gas is most likely associated with
the tilted molecular ring structure observed before in molecular emission and
IR continuum. The formaldehyde absorption shows small scale absorption which
requires a different distribution than the hydroxyl.

34
The categories of this paper are: chem-ph
16
The categories of this paper are: stat
12
The categories of this paper are: nucl-th
27
The categories of this paper are: comp-gas
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The categories of this paper are: cmp-lg
2
The categories of this paper are: math
14
The categories of this paper are: math-ph
29
The categories of this paper are: funct-an
9
The categories of this paper are: nlin
10
The categories of this paper are: q-bio
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The categories of this paper are: plasm-ph
19
The categories of this paper are: eess
18
The categories of this paper are: econ
17
The categories of this paper are: q-fin
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The categories of this paper are: bayes-an
5
The categories of this paper are: gr-qc