Magnetic Fields and Velocity Gradients in L1551: The Role of Stellar Feedback

TL;DR

This study investigates magnetic fields in the star-forming region L1551, revealing how stellar outflows influence magnetic field orientation and dust grain alignment through multi-instrument polarimetry and velocity gradient analysis.

Contribution

It combines polarimetry and velocity gradient techniques to analyze magnetic field structures and the impact of outflows in L1551, providing new insights into feedback effects on magnetic alignment.

Findings

Magnetic fields twist towards the protostar IRS 5.

Outflows significantly influence magnetic field orientation.

Polarization fraction correlates with intensity, affected by outflows.

Abstract

Magnetic fields play a crucial role in star formation, yet tracing them becomes particularly challenging, especially in the presence of outflow feedback in protostellar systems. We targeted the star-forming region L1551, notable for its apparent outflows, to investigate the magnetic fields. These fields were probed using polarimetry observations from the Planck satellite at 353 GHZ/849 $\mu$m, the SOFIA/HAWC+ measurement at 214 $\mu$m, and the JCMT/SCUPOL 850 $\mu$m survey. Consistently, all three measurements show that the magnetic fields twist towards the protostar IRS 5. Additionally, we utilized the Velocity Gradients Technique (VGT) on the $^{12}$CO (J = 1-0) emission data to distinguish the magnetic fields directly associated with the protostellar outflows. These were then compared with the polarization results. Notably, in the outskirts of the region, these measurements generally align. However, as one approaches the center of IRS 5, the measurements tend to yield mostly perpendicular relative orientations. This suggests that the outflows might be dynamically significant from a scale of approximately $\sim0.2$~pc, causing the velocity gradient to change direction by 90 degrees. Furthermore, we discovered that the polarization fraction $p$ and the total intensity $I$ correlate as $p \propto I^{-\alpha}$. Specifically, $\alpha$ is approximately $1.044\pm0.06$ for SCUPOL and around $0.858\pm0.15$ for HAWC+. This indicates that the outflows could significantly impact the alignment of dust grains and magnetic fields in the L1551 region.