Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: 1.3mm polarized emission in the circumstellar disk of a massive
  protostar   We present the first resolved observations of the 1.3mm polarized emission
from the disk-like structure surrounding the high-mass protostar Cepheus A HW2.
These CARMA data partially resolve the dust polarization, suggesting an uniform
morphology of polarization vectors with an average position angle of 57 degrees
and an average polarization fraction of 2.0%. The distribution of the
polarization vectors can be attributed to (1) the direct emission of
magnetically aligned grains of dust by a uniform magnetic field, or (2) the
pattern produced by the scattering of an inclined disk. We show that both
models can explain the observations, and perhaps a combination of the two
mechanisms produce the polarized emission. A third model including a toroidal
magnetic field does not match the observations. Assuming scattering is the
polarization mechanism, these observations suggest that during the first few
10000 years of high-mass star formation, grain sizes can grow from 1 to several
10s micron.

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The categories of this paper are: physics
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The categories of this paper are: quant-ph
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The categories of this paper are: stat
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The categories of this paper are: nlin
10
The categories of this paper are: q-bio
32
The categories of this paper are: atom-ph
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The categories of this paper are: math
34
The categories of this paper are: chem-ph
25
The categories of this paper are: patt-sol
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The categories of this paper are: bayes-an
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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: adap-org
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The categories of this paper are: hep-th
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The categories of this paper are: chao-dyn
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The categories of this paper are: acc-phys