Highly Ordered and Pinched Magnetic Fields in the Class 0 Protobinary System L1448 IRS 2

Woojin Kwon*, Ian W. Stephens, John J. Tobin, Leslie W. Looney, Zhi-Yun Li, Floris F. S. van der Tak, Richard M. Crutcher

*Corresponding author for this work

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Abstract

We have carried out polarimetric observations with the Atacama Large Millimeter/submillimeter Array toward the Class 0 protostellar system L1448 IRS 2, which is a protobinary 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 (̃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; though, 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 nonideal magnetohydrodynamic 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. This also suggests that early disk formation can happen even in young stellar objects with a strong primordial magnetic field.
Original languageEnglish
JournalThe Astrophysical Journal
Volume879
Issue number1
DOIs
Publication statusPublished - 1-Jul-2019

Keywords

  • magnetic fields
  • stars: formation
  • stars: protostars
  • submillimeter: ISM
  • Astrophysics - Solar and Stellar Astrophysics
  • Astrophysics - Astrophysics of Galaxies

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