Examining Turbulence in Galactic Molecular Clouds - II: Continuity of Turbulence Cascading in a Portion of the Local Arm

Abstract

We use 12CO (J=1-0) MWISP data to study turbulence in a segment of the Local Arm. Velocity
slices at different kinematic distances show similar spatial power spectra (SPSs) and structure functions
(SFs), demonstrating that the entire region forms a single turbulent field with a cascade extending
from ∼ 400 pc to sub-parsec scales. The SPS slopes of both the intensity and velocity fields exhibit
a systematic scale dependence that approaches the values expected from turbulence models. Cloudto-cloud VSFs follow similar trends to the pixel-by-pixel VSFs in the extended self-similarity (ESS)
scaling, indicating that velocity differences among clouds arise from large-scale turbulent motions.
Velocity- and intensity-increment maps reveal filamentary, intermittent structures. The PDFs of the
velocity increments display strong non-Gaussianity and are well fitted by the normal inverse gaussian
(NIG) distribution, whereas the intensity increments show much weaker tails. A simple energetic
estimate suggests that Galactic differential rotation is able to supply the large-scale shear required to
maintain the observed turbulence.