Instruct: Identify the main and secondary category of Arxiv papers based on the titles
Query: Discovery of a close pair of faint dwarf galaxies in the halo of
  Centaurus A
3
The categories of this paper are: physics
12
The categories of this paper are: nucl-th
24
The categories of this paper are: dg-ga
10
The categories of this paper are: q-bio
8
The categories of this paper are: hep-ex
22
The categories of this paper are: chao-dyn
29
The categories of this paper are: funct-an
15
The categories of this paper are: nucl-ex
25
The categories of this paper are: patt-sol
31
The categories of this paper are: ao-sci
13
The categories of this paper are: quant-ph
19
The categories of this paper are: eess
26
The categories of this paper are: bayes-an
5
The categories of this paper are: gr-qc
17
The categories of this paper are: q-fin
20
The categories of this paper are: acc-phys