The protostars in Orion: Characterizing the properties of their magnetized envelopes

TL;DR

This study links the physical and magnetic properties of protostellar envelopes in Orion, revealing how magnetic field morphology influences envelope fragmentation, disk size, and magnetic braking efficiency.

Contribution

It provides new insights into how envelope magnetic field morphology correlates with protostellar properties and fragmentation, using high-resolution polarization observations.

Findings

Hourglass magnetic fields associate with larger envelope mass and lower velocity dispersion.

Magnetic field morphology influences disk size and magnetic braking efficiency.

Magnetic field misalignment reduces magnetic braking, allowing larger disks to form.

Abstract

We present a study connecting the physical properties of protostellar envelopes to the morphology of the envelope-scale magnetic field. We used the ALMA polarization observations of 61 young prtostars at 0.87 mm on $\sim400-3000$ au scales from the {\em B}-field Orion Protostellar Survey to infer the envelope-scale magnetic field, and used the dust emission to measure the envelope properties on comparable scales. We find that protostars showing standard-hourglass-field morphology tend to have larger masses and lower velocity dispersions in their envelopes, whereas systems with spiral-field morphologies have higher velocity dispersion. 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 that the fragmentation level is positively correlated with 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, specially 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.