Parallel and Perpendicular Alignments of Velocity Gradient and Magnetic Field observed in the Molecular Clouds L1478 and L1482

TL;DR

This study applies the Velocity Gradient Technique to molecular clouds L1478 and L1482, revealing the influence of magnetic fields and self-gravity on star formation regions through comparison with Planck polarization data.

Contribution

It introduces the application of VGT to specific molecular clouds and compares its results with Planck polarization, highlighting the effects of resolution and physical processes.

Findings

VGT results align with Planck in L1478, indicating weak self-gravity.

VGT results are perpendicular to Planck in L1482, indicating strong self-gravity.

Resolution differences can cause misalignment between measurements.

Abstract

Star formation is a complex process that typically occurs in dense regions of molecular clouds mainly regulated by magnetic fields, magnetohydrodynamic (MHD) turbulence, and self-gravity. However, it remains a challenging endeavor to trace the magnetic field and determine regions of gravitational collapse where the star is forming. Based on the anisotropic properties of MHD turbulence, a new technique termed Velocity Gradient Technique (VGT) has been proposed to address these challenges. In this study, we apply the VGT to two regions of the giant California Molecular Cloud (CMC), namely, L1478 and L1482, and analyze the difference in their physical properties. We use the $^{12}$CO (J = 2 - 1), $^{13}$CO (J = 2 - 1), and C$^{18}$O (J = 2 - 1) emission lines observed with the Heinrich Hertz Submillimeter Telescope. We compare VGT results calculated in the resolutions of $3.3'$ and $10'$ to Planck polarization at 353 GHz and $10'$ to determine areas of MHD turbulence dominance and self-gravity dominance. We show that the resolution difference can introduce misalignment between the two measurements. We find the VGT-measured magnetic fields globally agree with that from Planck in L1478 suggesting self-gravity's effect is insignificant. The best agreement appears in VGT-$^{12}$CO. As for L1482, the VGT measurements are statistically perpendicular to the Planck polarization indicating the dominance of self-gravity. This perpendicular alignment is more significant in VGT-$^{13}$CO and VGT-C$^{18}$O.