Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Deciphering the 3-D Orion Nebula-IV: The HH~269 flow emerges from the
  Orion-S Embedded Molecular Cloud   We have extended the membership and determined the 3-D structure of the large
(0.19 pc) HH~269 sequence of shocks in the Orion Nebula. All of the components
lie along a track that is highly tilted to the plane-of-the-sky and emerge from
within the Orion-S embedded molecular cloud. Their source is probably either
the highly obscured mm 9 source associated with a high N2H+ density core (more
likely) or the more distant star COUP 632 (less likely). The former must be
located in the Photon Dominated Region (PDR) underlying the ionized surface of
the Orion South Cloud, while the latter would be embedded within the cloud. The
flows seem to be episodic, with intervals of 1900 to 2600 years or 700 to 2600
years if COUP 632 is the source.

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The categories of this paper are: adap-org
3
The categories of this paper are: physics
5
The categories of this paper are: gr-qc
11
The categories of this paper are: hep-lat
18
The categories of this paper are: econ
35
The categories of this paper are: mtrl-th
10
The categories of this paper are: q-bio
0
The categories of this paper are: hep-ph
37
The categories of this paper are: supr-con
13
The categories of this paper are: quant-ph
22
The categories of this paper are: chao-dyn
19
The categories of this paper are: eess
31
The categories of this paper are: ao-sci
15
The categories of this paper are: nucl-ex
20
The categories of this paper are: acc-phys
25
The categories of this paper are: patt-sol