Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The Magnetic Field in the Star-forming Region Cepheus A from Water Maser
  Polarization Observations   We present linear and circular polarization observations of the water masers
in 4 distinct regions spread over 1x2 arcseconds around the HW2 high-mass young
stellar object in the Cepheus A star-forming region. We find magnetic fields
between 100-500 mG in the central maser region, which has been argued to trace
a circumstellar disk. The masers further from HW2 have field strengths between
30-100 mG. In all cases the magnetic field pressure is found to be similar to
the dynamic pressure, indicating that the magnetic field is capable of
controlling the outflow dynamics around HW2. In addition to several water maser
complexes observed before, we also detect a new maser filament, ~1 arcsec (~690
AU) East of HW2, which we interpret as a shocked region between the HW2 outflow
and the surrounding medium. We detect a linear polarization gradient along the
filament as well as a reversal of the magnetic field direction. This is thought
to mark the transition between the magnetic field associated with the outflow
and that found in the surrounding molecular cloud. In addition to the magnetic
field we determine several other physical properties of the maser region,
including density and temperatures as well as the maser beaming angles.

12
The categories of this paper are: nucl-th
29
The categories of this paper are: funct-an
9
The categories of this paper are: nlin
22
The categories of this paper are: chao-dyn
7
The categories of this paper are: hep-th
23
The categories of this paper are: solv-int
4
The categories of this paper are: cond-mat
10
The categories of this paper are: q-bio
0
The categories of this paper are: hep-ph
33
The categories of this paper are: plasm-ph
36
The categories of this paper are: cmp-lg
34
The categories of this paper are: chem-ph
11
The categories of this paper are: hep-lat
1
The categories of this paper are: cs
37
The categories of this paper are: supr-con
32
The categories of this paper are: atom-ph