Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A giant molecular cloud falling through the heart of Cygnus A: clues to
  the triggering of the activity   We present intermediate resolution near-IR long-slit spectroscopic data for
the nearby radio galaxy Cygnus A (3C 405) (obtained with the NIRSPEC
spectrograph on the Keck II telescope). The data reveal considerable complexity
in the near-IR emission line kinematics, including line splittings of 200-350
km/s and a mixture of narrow (FWHM ~200 km/s) and broad (FWHM ~700 km/s)
components to the emission lines. It is notable that the Pa alpha and H2
emission lines show markedly different kinematics, both on- and off-nucleus.
Overall, the data provide evidence for the presence of a giant molecular cloud
falling through the heart of the Cygnus A host galaxy, the motion of which is
not driven by the AGN itself. We suggest that this cloud may be connected to
the triggering of the activity in this highly powerful AGN. We also detect
split H2 components on the nucleus that are likely to originate in the
circum-nuclear torus.

16
The categories of this paper are: stat
29
The categories of this paper are: funct-an
26
The categories of this paper are: bayes-an
20
The categories of this paper are: acc-phys
36
The categories of this paper are: cmp-lg
19
The categories of this paper are: eess
31
The categories of this paper are: ao-sci
22
The categories of this paper are: chao-dyn
3
The categories of this paper are: physics
27
The categories of this paper are: comp-gas
2
The categories of this paper are: math
23
The categories of this paper are: solv-int
10
The categories of this paper are: q-bio
32
The categories of this paper are: atom-ph
25
The categories of this paper are: patt-sol
1
The categories of this paper are: cs