Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Multi-wavelength carbon recombination line observations with the VLA
  toward an UCHII region in W48: Physical properties and kinematics of neutral
  material   Using the Very Large Array (VLA) the C76$\alpha$ and C53$\alpha$
recombination lines (RLs) have been detected toward the ultra-compact \HII\
region (UCHII region) G35.20$-$1.74. We also obtained upper limits to the
carbon RLs at 6 cm (C110$\alpha$ & C111$\alpha$) and 3.6 cm (C92$\alpha$)
wavelengths with the VLA. In addition, continuum images of the W48A complex
(which includes G35.20$-$1.74) are made with angular resolutions in the range
14\arcsec to 2\arcsec. Modeling the multi-wavelength line and continuum data
has provided the physical properties of the UCHII region and the
photodissociation region (PDR) responsible for the carbon RL emission. The gas
pressure in the PDR, estimated using the derived physical properties, is at
least four times larger than that in the UCHII region. The dominance of
stimulated emission of carbon RLs near 2 cm, as implied by our models, is used
to study the relative motion of the PDR with respect to the molecular cloud and
ionized gas. Our results from the kinematical study are consistent with a
pressure-confined UCHII region with the ionizing star moving with respect to
the molecular cloud. However, based on the existing data, other models to
explain the extended lifetime and morphology of UCHII regions cannot be ruled
out.

3
The categories of this paper are: physics
2
The categories of this paper are: math
29
The categories of this paper are: funct-an
19
The categories of this paper are: eess
13
The categories of this paper are: quant-ph
23
The categories of this paper are: solv-int
35
The categories of this paper are: mtrl-th
37
The categories of this paper are: supr-con
15
The categories of this paper are: nucl-ex
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The categories of this paper are: adap-org
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The categories of this paper are: gr-qc
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The categories of this paper are: cond-mat
36
The categories of this paper are: cmp-lg
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The categories of this paper are: econ
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The categories of this paper are: comp-gas
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The categories of this paper are: atom-ph