1.3 mm POLARIZED EMISSION in the CIRCUMSTELLAR DISK of A MASSIVE PROTOSTAR

GIRART, J.M.; SEGURA-COX, D.; FERNÁNDEZ-LÓPEZ, M.; LOONEY, L.; ESWARAIAH, C.; STEPHENS, I.W.; CURIEL, S.; LAI, S.-P.

ASTROPHYSICAL JOURNAL

IOP PUBLISHING LTD

Año: 2016 vol. 832

0004-637X

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° ± 6° 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 from1 mm to several 10s μm.