Tracing magnetic field morphology using the Velocity Gradient Technique
  in the presence of CO self-absorption
  Probing magnetic fields in self-gravitating molecular clouds are generally
difficult even with the use of the polarimetry. Based on the properties of
magneto-hydrodynamic (MHD) turbulence and turbulent reconnection, Velocity
Gradient Technique (VGT) provides a new way in tracing magnetic field
orientation and strength based on the spectroscopic data. Our study tests the
applicability of VGT in various molecular tracers, e.g. 12CO, 13CO, and C18O.
By inspecting synthetic molecular line maps of CO isotopologue generated
through radiative transfer calculations, we show that the VGT method can be
successfully applied in probing the magnetic field direction in the diffuse
interstellar medium as well as in self-gravitating molecular clouds.
