Lunch talk on Oct. 20, 2025

Multiscale studies of turbulence and shocks in ISM

Speaker: Xunchuan Liu (Leiden University)

Venue: SWIFAR Building 2111

Time: 12:45 PM, Monday, Oct. 20, 2025

Abstract: 

 Turbulence shapes the interstellar medium (ISM) across multiple scales. Turbulence shapes the interstellar medium (ISM) across multiple scales. FAST H I observations of the G165 very high-velocity cloud (VHVC) reveal a complex filamentary network induced by supersonic turbulence, while the high-velocity cloud AC-III exhibits droplet-like subclumps shaped by ram pressure and internal interactions, suggesting that turbulence in HVCs may originate from interactions between droplets. At molecular-cloud scales, we present the first high-Galactic-latitude 100 square degrees CO survey at sub-arcminute resolution of the Polaris Flare, ideal for studying HI-to-H2  formation, the distribution of dust in multiphase gas, and the role of turbulence in early cloud evolution. Lognormal PDFs are common in atomic and molecular clouds, though some deviations occur. Theoretically, skewed density probability distribution functions (PDFs) at high Mach numbers reflect distinct cascading strategies: atomic clouds exhibit low-density skewness, while gravity-dominated star-forming molecular clouds tend to appear high-density tails. At protostellar scales, we find that SO and SO2 are good tracers of disk-accretion induced shocks in the inner envelope, the circulation ring between the inner envelope and disk, and accretion streamers, supporting the idea that shocks may refresh the chemistry of gas accreted into the protoplanetary disk.

Report PPT:  SWIFAR_Xunchuan Liu.pdf