Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The Cone-Like H-alpha Nebula in NGC 4945: A Galactic Superwind Bow Shock
  ?   We find that a non-axisymmetric bow shock model, with an appropriate choice
of parameters, could fit the line splitting velocity field of the cone-like
H$\alpha$ nebula in NGC 4945 better than a canonical cone model. Meanwhile, the
bow shock model could also reproduce the morphology of the H$\alpha$ nebula.
The bow shock results from the interaction of the galactic superwinds with a
giant HII region. It is implied that the starburst ring or disk around the
galactic nucleus should be generating strong winds, and the bright H$\alpha$
knot northwest of the nucleus be suffering an anisotropic mass loss process.

31
The categories of this paper are: ao-sci
18
The categories of this paper are: econ
0
The categories of this paper are: hep-ph
23
The categories of this paper are: solv-int
35
The categories of this paper are: mtrl-th
7
The categories of this paper are: hep-th
5
The categories of this paper are: gr-qc
20
The categories of this paper are: acc-phys
27
The categories of this paper are: comp-gas
8
The categories of this paper are: hep-ex
11
The categories of this paper are: hep-lat
37
The categories of this paper are: supr-con
16
The categories of this paper are: stat
13
The categories of this paper are: quant-ph
4
The categories of this paper are: cond-mat
14
The categories of this paper are: math-ph