Highly Ordered and Pinched Magnetic Fields in the Class 0 Proto-Binary System L1448 IRS 2

We have carried out polarimetric observations with the Atacama Large Millimeter/submillimeter Array (ALMA) toward the Class 0 protostellar system L1448 IRS 2, which is a proto-binary embedded within a flattened, rotating structure, and for which a hint of a central disk has been suggested, but whose...

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Bibliographic Details
Published in:arXiv.org 2019-05
Main Authors: Kwon, Woojin, Stephens, Ian, Tobin, John, Looney, Leslie, Zhi-Yun, Li, van der Tak, Floris, Crutcher, Richard
Format: Article
Language:English
Subjects:
Binary stars
Braking
Companion stars
Depolarization
Embedded systems
Field strength
Fluid dynamics
Magnetic fields
Magnetohydrodynamics
Morphology
Outflow
Polarimetry
Polarization
Protostars
Radio telescopes
Star & galaxy formation
Star formation
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Summary:We have carried out polarimetric observations with the Atacama Large Millimeter/submillimeter Array (ALMA) toward the Class 0 protostellar system L1448 IRS 2, which is a proto-binary embedded within a flattened, rotating structure, and for which a hint of a central disk has been suggested, but whose magnetic fields are aligned with the bipolar outflow on the cloud core scale. Our high sensitivity and high resolution (\(\sim 100\) au) observations show a clear hourglass magnetic field morphology centered on the protostellar system, but the central pattern is consistent with a toroidal field indicative of a circumstellar disk, although other interpretations are also possible, including field lines dragged by an equatorial accretion flow into a configuration parallel to the midplane. If a relatively large disk does exist, it would suggest that the magnetic braking catastrophe is averted in this system, not through a large misalignment between the magnetic and rotation axes, but rather through some other mechanisms, such as non-ideal magneto-hydrodynamic effects and/or turbulence. We have also found a relationship of decreasing polarization fractions with intensities and the various slopes of this relationship can be understood as multiple polarization mechanisms and/or depolarization from a changing field morphology. In addition, we found a prominent clumpy depolarization strip crossing the center perpendicular to the bipolar outflow. Moreover, a rough estimate of the magnetic field strength indicates that the field is strong enough to hinder formation of a rotationally supported disk, which is inconsistent with the feature of a central toroidal field.
ISSN:2331-8422
DOI:10.48550/arxiv.1805.07348