Probing the magnetic field structure in the W3 molecular cloud

This paper presents polarization maps of the central 3′ × 5′ region of the W3 molecular cloud at farinfrared (60 and 100 μm) and submillimeter (350 μm) wavelengths. We use the multiwavelength polarization measurements to differentiate between the emission in warm and cool dust components. We infer that the submillimeter observations trace a layer of cool dust with high column density, which we attribute to a large scale ridge of material. This ambient ridge has an orderly magnetic field with evidence for "hourglass" field structure; however, the field structure is qualitatively different in size and orientation compared to previous studies. The far-infrared measurements are dominated by warm dust surrounding evolved H II regions or embedded young stars. The warm dust, in contrast to the ridge, has a disrupted magnetic field that varies rapidly in the plane of the sky and along the line of sight, suggesting that the field has been distorted by the expansion of H II regions.