1.3 mm POLARIZED EMISSION IN THE CIRCUMSTELLAR DISK OF A MASSIVE PROTOSTAR

• Published in: The Astrophysical journal Vol. 832; no. 2; pp. 200 - 207
• Main Authors: Fernández-López, M., Stephens, I. W., Girart, J. M., Looney, L., Curiel, S., Segura-Cox, D., Eswaraiah, C., Lai, S.-P.
• Format: Journal Article
• Language: English
• Published: Philadelphia The American Astronomical Society 01.12.2016; IOP Publishing
• Subjects: Accretion disks; Astrophysics; ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; Cepheus constellation; COSMIC DUST; DISTRIBUTION; Dust; EMISSION; Grain size; ISM: individual objects (Cepheus A HW2); ISM: magnetic fields; MAGNETIC FIELDS; MASS; Massive stars; Morphology; POLARIZATION; PROTOSTARS; SCATTERING; Star & galaxy formation; STAR EVOLUTION; Star formation; STARS; stars: formation; techniques: polarimetric
• ISSN: 0004-637X; 1538-4357
• DOI: 10.3847/0004-637X/832/2/200

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 ° 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 from 1 m to several 10s m.