Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The X-ray properties of the merging galaxy pair NGC 4038/9 - the
  Antennae   We report the results of an X-ray spectral imaging observation of the
Antennae with the ROSAT PSPC. 55% of the soft X-ray flux from the system is
resolved into discrete sources, including components identified with the
galactic nuclei and large HII regions, whilst the remainder appears to be
predominantly genuinely diffuse emission from gas at a temperature ~4x10^6 K.
The morphology of the emission is unusual, combining a halo which envelopes the
galactic discs, with what appears to be a distorted, but well-collimated
bipolar outflow. We derive physical parameters for the hot gas in both diffuse
components, which are of some interest, given that the Antennae probably
represents an elliptical galaxy in the making.

23
The categories of this paper are: solv-int
33
The categories of this paper are: plasm-ph
11
The categories of this paper are: hep-lat
37
The categories of this paper are: supr-con
35
The categories of this paper are: mtrl-th
34
The categories of this paper are: chem-ph
1
The categories of this paper are: cs
18
The categories of this paper are: econ
2
The categories of this paper are: math
12
The categories of this paper are: nucl-th
10
The categories of this paper are: q-bio
25
The categories of this paper are: patt-sol
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The categories of this paper are: eess
14
The categories of this paper are: math-ph
36
The categories of this paper are: cmp-lg
3
The categories of this paper are: physics