Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: VLA Observations of DG Tau's Radio Jet: A highly collimated thermal
  outflow   The active young protostar DG Tau has an extended jet that has been well
studied at radio, optical, and X-ray wavelengths. We report sensitive new VLA
full-polarization observations of the core and jet between 5 GHz and 8 GHz. Our
high angular resolution observation at 8 GHz clearly shows an unpolarized inner
jet with a size 42 AU (0.35") extending along a position angle similar to the
optical-X ray outer jet. Using our nearly coeval 2012 VLA observations, we find
a spectral-index=+0.46+/-0.05, which combined with the lack of polarization, is
consistent with bremsstrahlung (free-free) emission, with no evidence for a
non-thermal coronal component. By identifying the end of the radio jet as the
optical depth unity surface, and calculating the resulting emission measure, we
find our radio results are in agreement with previous optical line studies of
electron density and consequent mass-loss rate. We also detect a weak radio
knot at 5 GHz located 7" from the base of the jet, coincident with the inner
radio knot detected by Rodriguez et al. (2012) in 2009 but at lower surface
brightness. We interpret this as due to expansion of post-shock ionized gas in
the three years between observations.

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The categories of this paper are: nlin
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The categories of this paper are: q-bio
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The categories of this paper are: q-alg
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The categories of this paper are: econ
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The categories of this paper are: dg-ga
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The categories of this paper are: cond-mat
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The categories of this paper are: nucl-th
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The categories of this paper are: funct-an
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The categories of this paper are: comp-gas
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The categories of this paper are: ao-sci
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The categories of this paper are: cmp-lg
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The categories of this paper are: atom-ph
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The categories of this paper are: alg-geom
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The categories of this paper are: adap-org
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The categories of this paper are: physics
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The categories of this paper are: stat