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

Abstract

We use ${}^{12}$CO (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 $\sim 400$ 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. Cloud-to-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.

12 pages and 7 Figures