We explore how the velocity gradient technique (VGT) can be applied to absorbing media in the case of 13CO 2-1 emission. The VGT is a new way to trace magnetic fields in the plane of the sky using only spectroscopic observations. We apply the VGT to magnetohydrodynamic turbulence simulations that have been post-processed to include 13CO 2-1 emission and we calculate the velocity centroid gradients. We find that the velocity centroid gradients trace the projected magnetic field in media with different 13CO abundances, densities and optical depths. Our study opens up the possibility of using velocity centroid gradients to trace magnetic fields in molecular clouds using 13CO emission.
González-Casanova, Diego F.; Lazarian, A.; Burkhart, Blakesley
2019, Monthly Notices of the Royal Astronomical Society, 483, 1287