| 报告摘要： |
Molecular gas is the raw material for forming stars and galaxies. Unfortunately, molecular hydrogen (H2) is undetectable due to the lack of a permanent dipole moment and accessible transitions in the cold phase. The understanding of cold molecular gas is largely based on the measurements of the abundant tracers such as CO. However, observations in the past 20 years found that a significant fraction of molecular gas (20%-80%, refer to as "DMG") cannot be traced by CO emission surveys. In this talk, I will introduce my recent works on quantifying molecular gas contents with different tracers in low-density gas. Combining high-sensitivity observations with numerical modeling, we are able to constrain the key parameters (e.g., cosmic-ray ionization rate) that regularize the formation and evolution of molecules.
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