Statistical tracing of turbulent magnetic fields in the optically thick interstellar medium.

Based on high-resolution 3D data cubes from a magnetohydrodynamic (MHD) turbulence simulation, we study how to reveal the direction of the magnetic field within the optically thick interstellar medium by using the velocity gradient technique (VGT), correlation function anisotropy (CFA), and principal component analysis of anisotropies (PCAA). Considering the CO molecular tracers as a tracing method for radiative transfer processes, we find that the VGT and CFA can successfully trace the orientation of mean magnetic fields, which is in good agreement with the low-resolution numerical results obtained in the case of an optically thin medium. Similar to the simulation of an optically thin ISM, our simulations show that PCCA is still unusable in optically thick media. The synergetic application of the VGT and CFA to high-resolution spectroscopic observations is expected to yield valuable information on the interstellar magnetic field. [ABSTRACT FROM AUTHOR]