Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The near-infrared excitation of the HH211 protostellar outflow   The protostellar outflow HH211 is of considerable interest since it is
extremely young and highly collimated. Here, we explore the outflow through
imaging and spectroscopy in the near-infrared to determine if there are further
diagnostic signatures of youth. We confirm the detection of a near-infrared
continuum of unknown origin. We propose that it is emitted by the driving
millimeter source, escapes the core through tunnels, and illuminates features
aligning the outflow. Narrow-band flux measurements of these features contain
an unusually large amount of continuum emission. [Fe II] emission has been
detected and is restricted to isolated condensations. However, the
characteristics of vibrational excitation of molecular hydrogen resemble those
of older molecular outflows. We attempt to model the ordered structure of the
western outflow as a series of shocks, finding that bow shocks with J-type
dissociative apices and C-type flanks are consistent. Moreover, essentially the
same conditions are predicted for all three bows except for a systematic
reduction in speed and density with distance from the driving source. We find
increased K-band extinctions in the bright regions as high as 2.9 magnitudes
and suggest that the bow shocks become visible where the outflow impacts on
dense clumps of cloud material. We propose that the outflow is carved out by
episodes of pulsating jets. The jets, driven by central explosive events, are
responsible for excavating a central tunnel through which radiation temporarily
penetrates.

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The categories of this paper are: cs
32
The categories of this paper are: atom-ph
34
The categories of this paper are: chem-ph
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The categories of this paper are: math
18
The categories of this paper are: econ
7
The categories of this paper are: hep-th
26
The categories of this paper are: bayes-an
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The categories of this paper are: nucl-th
35
The categories of this paper are: mtrl-th
37
The categories of this paper are: supr-con
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The categories of this paper are: physics
21
The categories of this paper are: adap-org
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The categories of this paper are: funct-an
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The categories of this paper are: patt-sol
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The categories of this paper are: cond-mat
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The categories of this paper are: cmp-lg