Using The Velocity Anisotropy Technique To Investigate Interstellar Magnetohydrodynamic Turbulence

Missy McIntosh, Blakesley Burkhart
2016 Zenodo  
Magnetohydrodynamic (MHD) turbulence in the interstellar medium (ISM) influences star formation and subsequently the way our Galaxy evolves. Direct observations of magnetic fields for studying MHD turbulence can be difficult and costly to obtain; as an alternative, we explore a technique called velocity anisotropy to probe MHD turbulence. We apply the velocity anisotropy technique (VAT) in CO radiative transfer MHD simulations for the first time and also to non-synthetic observations for the
more » ... st time. We find that for optically thin radiative transfer simulations, the sub-Alfvénic and super-Alfvénic regimes are indistinguishable. For the optically thick case the regimes were distinguishable. We then apply the VAT to 12CO and 13CO emission line observations of the Taurus Molecular Cloud, and compare results with that of a principal component analysis (PCA) technique detailed in Heyer & Brunt (2011). We find that increased velocity anisotropy did not correspond to regions of lower gas column density/visual extinction as it did when analyzed with PCA, though this may be due to the selection of region size. We also found 12CO emission to show more velocity anisotropy than 13CO emission, in agreement with the PCA analysis. As a preface to and to supply context for the VAT and its usefulness, we first overview the ISM, turbulence, MHD turbulence in the ISM, and the interstellar magnetic field. We discuss the challenges of observing magnetic fields and the need for methods like VAT to study these fields, MHD turbulence, and the way our Galaxy evolves.
doi:10.5281/zenodo.50082 fatcat:jmhbrrr7sjccne6nte6i5pfuee