Turbulence in the Inner and Outer Galaxy
李悅寧 Yueh-Ning Lee (NTNU)
※Keywords:
Turbulence, CHIMPS, Molecular Clouds, JCMT
※Description:
The nature of turbulence in molecular clouds is one of the driving factors that influence star formation efficiency. It is speculated that the high star formation efficiency observed in spiral-arm clouds is linked to the prevalence of compressive (curl-free) turbulent modes, while the shear-driven solenoidal (divergence-free) modes appear to be the main cause of the low star formation efficiency that characterizes clouds in the Central Molecular Zone (CMZ). Turbulent modes also vary locally and at different scales within a cloud: turbulent motions surrounding the main star-forming regions display a strongly compressive nature. This evidence points to the solenoidal modes being an agent for the variability of star formation efficiency.
We estimated the relative amount of power in the solenoidal modes (solenoidal fraction) in a large sample of Galactic molecular clouds in the CO Heterodyne Inner Milky Way Plane Survey (CHIMPS), finding a negative correlation between the solenoidal fraction and star-formation efficiency (estimated independently). This feature is consistent with the hypothesis that solenoidal modes prevent or slow down the collapse of dense cores. In addition, solenoidal turbulence appears to be higher in the Inner Galaxy (the region swept by the rotation of the Galactic bar). Outside the Inner Galaxy, the slowly, monotonically declining values suggest that the solenoidal fraction is unaffected by the spiral arms.
In this project, we will use the follow-up survey to CHIMPS, CHIMPS 2 to extend the analysis of the solenoidal modes to the clouds in the Inner Galaxy, Galactic Center and Outer Galaxy. We aim to explore how different Galactic environments affect turbulence in molecular gas. Finally, we will compare the results to the trends observed for CHIMPS sources.
※Required Background:
Unix/Linux experience, Programming Languages such as Python Scripting, Fortran 90, or C/C++. Fundamental knowledge of physics.