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.
@article{arxiv.1610.03407,
title = {1.3mm polarized emission in the circumstellar disk of a massive protostar},
author = {M. Fernández-López and I. W. Stephens and J. M. Girart and L. Looney and S. Curiel and D. Segura-Cox and C. Eswaraiah and S. -P. Lai},
journal= {arXiv preprint arXiv:1610.03407},
year = {2016}
}
Comments
Accepted for publication in ApJ, 9 pages, 5 figures, 2 tables