Testing Magnetic Field Models for the Class 0 Protostar L1527

TL;DR

This study compares polarization observations of the protostar L1527 with four ideal-MHD collapse models to determine which best matches the magnetic field structure, revealing limitations of non-turbulent models in explaining observed features.

Contribution

It evaluates the agreement between observed polarization vectors and four different ideal-MHD collapse models, highlighting the importance of large-area polarization measurements.

Findings

Weak aligned model best matches observed magnetic field structure.

Weak orthogonal model produces the observed circumstellar disk.

Non-turbulent ideal-MHD models may not fully explain L1527's collapse.

Abstract

For the Class 0 protostar, L1527, we compare 131 polarization vectors from SCUPOL/JCMT, SHARP/CSO and TADPOL/CARMA observations with the corresponding model polarization vectors of four ideal-MHD, non-turbulent, cloud core collapse models. These four models differ by their initial magnetic fields before collapse; two initially have aligned fields (strong and weak) and two initially have orthogonal fields (strong and weak) with respect to the rotation axis of the L1527 core. Only the initial weak orthogonal field model produces the observed circumstellar disk within L1527. This is a characteristic of nearly all ideal-MHD, non-turbulent, core collapse models. In this paper we test whether this weak orthogonal model also has the best agreement between its magnetic field structure and that inferred from the polarimetry observations of L1527. We found that this is not the case; based on the polarimetry observations the most favored model of the four is the weak aligned model. However, this model does not produce a circumstellar disk, so our result implies that a non-turbulent, ideal-MHD global collapse model probably does not represent the core collapse that has occurred in L1527. Our study also illustrates the importance of using polarization vectors covering a large area of a cloud core to determine the initial magnetic field orientation before collapse; the inner core magnetic field structure can be highly altered by a collapse and so measurements from this region alone can give unreliable estimates of the initial field configuration before collapse.