1.3 mm Polarized Emission in the Circumstellar Disk of a Massive Protostar
Abstract
We present the first resolved observations of the 1.3 mm polarized emission from the disk-like structure surrounding the high-mass protostar Cepheus A HW2. These CARMA data partially resolve the dust polarization, suggesting a uniform morphology of polarization vectors with an average position angle of 57^\circ +/- 6^\circ and an average polarization fraction of 2.0 % +/- 0.4 % . 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 produces 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 104 years of high-mass star formation, grain sizes can grow from 1 μ {{m}} to several 10s μm.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- December 2016
- DOI:
- 10.3847/0004-637X/832/2/200
- arXiv:
- arXiv:1610.03407
- Bibcode:
- 2016ApJ...832..200F
- Keywords:
-
- ISM: individual objects: Cepheus A HW2;
- ISM: magnetic fields;
- polarization;
- stars: formation;
- techniques: polarimetric;
- Astrophysics - Solar and Stellar Astrophysics;
- Astrophysics - Astrophysics of Galaxies
- E-Print:
- Accepted for publication in ApJ, 9 pages, 5 figures, 2 tables