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Abstract TheB-field Orion Protostellar Survey (BOPS) recently obtained polarimetric observations at 870μm toward 61 protostars in the Orion molecular clouds with ∼1″ spatial resolution using the Atacama Large Millimeter/submillimeter Array. From the BOPS sample, we selected the 26 protostars with extended polarized emission within a radius of ∼6″ (2400 au) around the protostar. This allows us to have sufficient statistical polarization data to infer the magnetic field strength. The magnetic field strength is derived using the Davis–Chandrasekhar–Fermi method. The underlying magnetic field strengths are approximately 2.0 mG for protostars with a standard hourglass magnetic field morphology, which is higher than the values derived for protostars with rotated hourglass, spiral, and complex magnetic field configurations (≲1.0 mG). This suggests that the magnetic field plays a more significant role in envelopes exhibiting a standard hourglass field morphology, and a value of ≳2.0 mG would be required to maintain such a structure at these scales. Furthermore, most protostars in the sample are slightly supercritical, with mass-to-flux ratios ≲3.0. In particular, the mass-to-flux ratios for all protostars with a standard hourglass magnetic field morphology are lower than 3.0. However, these ratios do not account for the contribution of the protostellar mass, which means they are likely significantly underestimated.
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This content will become publicly available on February 24, 2026
The Protostars in Orion: Characterizing the Properties of Their Magnetized Envelopes
Abstract We present a study connecting the physical properties of protostellar envelopes to the morphology of the envelope-scale magnetic field. We used the Atacama Large Millimeter/submillimeter Array (ALMA) polarization observations of 61 young protostars at 0.87 mm on ~400–3000 au scales from theB-field Orion Protostellar Survey to infer the envelope-scale magnetic field, and we used the dust emission to measure the envelope properties on comparable scales. We find that protostars showing standard hourglass magnetic field morphology tend to have larger masses, and the nonthermal velocity dispersion is positively correlated with the bolometric luminosity and dust temperature of the envelope. Combining with the disk properties taken from the Orion VLA/ALMA Nascent Disk and Multiplicity survey, we connect envelope properties to fragmentation. Our results show a positive correlation between the fragmentation level and the angle dispersion of the magnetic field, suggesting that the envelope fragmentation tends to be suppressed by the magnetic field. We also find that protostars exhibiting standard hourglass magnetic field structure tend to have a smaller disk and smaller angle dispersion of the magnetic field than other field configurations, especially the rotated hourglass, but also the spiral and others, suggesting a more effective magnetic braking in the standard hourglass morphology of magnetic fields. Nevertheless, significant misalignment between the magnetic field and outflow axes tends to reduce magnetic braking, leading to the formation of larger disks.
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- PAR ID:
- 10608981
- Publisher / Repository:
- American Astronomical Society
- Date Published:
- Journal Name:
- The Astrophysical Journal
- Volume:
- 981
- Issue:
- 1
- ISSN:
- 0004-637X
- Page Range / eLocation ID:
- 30
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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