Making Clouds Less Cloudy: Modelling ISM With Simulations And Synthetic Observations

Abstract

Giant molecular clouds (GMCs) are the birthplaces of stars. Multiple physics mechanisms including gravity, magnetic fields, and radiation interplay within these clouds, and set the initial conditions for star formation. However, the exact role of each mechanism is still unclear, largely due to observational biases arising from projection, chemical, and excitation effects. Simulations and synthetic observations are therefore necessary for realistic interpretation of observations of the GMC formation and evolution processes.

This thesis focuses on building a comprehensive picture of the structure of GMCs using this approach. The first part of the thesis applies a theoretical model that can predict the 3D density structure of GMCs to determine the SFEs of nearby GMCs. The second part of the thesis examines measurements of magnetic field strengths, and points out that due to chemical and excitation biases the role of magnetic fields in GMC formation is less important than suggested by earlier interpretations of observations. The third part of this thesis reveals a significant discrepancy between two main star formation rate measurement methods, young stellar object counting and hydrogen recombination line observation, demonstrates how this discrepancy changes with local GMC conditions, and provides a calibration model for massive GMCs. I conclude this thesis by suggesting avenues for future studies.