Astronomy and Astrophysics – Astronomy
Scientific paper
May 1998
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1998aas...192.1017g&link_type=abstract
American Astronomical Society, 192nd AAS Meeting, #10.17; Bulletin of the American Astronomical Society, Vol. 30, p.830
Astronomy and Astrophysics
Astronomy
3
Scientific paper
Theories suggest that magnetic fields are an important parameter in molecular cloud dynamics and star formation. Dust grains are preferrentially aligned in the presence of magnetic fields with their greatest average projection orthogonal to the field lines. Hence, magnetic fields can be observed with millimeter-wave polarimetry of thermal dust continuum emission. We present a lambda =1.3 mm continuum polarization map of DR 21. The polarization and position angles are very uniform and the inferred magnetic field is nearly orthogonal to the cloud elongation. We place an upper limit of 5 mG on the average magnetic field strength. Turbulent gas motions are a more signficant source of support against self gravity in the cloud core than magnetic fields or thermal pressure. We also report a polarimetry survey of 14 star-forming cloud cores. We compare the physical parameters derived from far infrared photometry of nine of these to our polarimetry. Consistent with theoretical expectations, the polarizations do not depend on the 1.3 mm optical depth, dust emission temperature, or dust emissivity spectral index. We combined our observations with 800 mu m polarimetry from the literature. The sky-plane projection of the magnetic fields lines in the seven elongated cloud cores with polarizations detections >3sigma appear randomly distributed with respect to the position angles of the cloud core elongations. This implies that magnetic fields do not provide substantial anisotropic support against self gravity in a uniform way in this sample of cloud cores. The magnetic fields also appear randomly oriented with respect to the Galactic plane. This implies that the field lines are consistent with the random component of Galactic magnetic field.
Glenn Jason
Walker Christopher K.
Young Erick T.
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