The Dynamics of Stellar Wind-Driven Bubbles and Their Effect on Star Formation in Giant Molecular Clouds

Abstract

Star formation in Giant Molecular Clouds (GMCs) is of fundamental importance to our under- standing of star formation in our universe since it is in these massive, transient objects where almost all stars are formed. To understand the process of star formation in GMCs one must understand how star formation feedback from the massive stars that form within them acts to halt the star formation process. Massive stars (M∗ ≳ 8M⊙) can inject significant amounts of energy in to the surrounding cloud, blowing apart the cloud and halting star formation. One way this can happen is when the radiative energy from these stars is injected directly in to their atmospheres, resulting in massive outflows moving at velocities of > 1000kms−1. These winds shock when they impact the ambient medium, creating highly over-pressurized, extremely hot T ∼ 108 K gas that expands rapidly in to the surrounding cloud. In this thesis, we seek to understand this process in the context of realistic star forming environments. In this dissertation, we show how turbulent mixing between the wind-driven bubble and the surroundings can lead to efficient cooling at the T ∼ 104 K gas created through this mixing. We demonstrate that this cooling can be sufficient to cause the bubble’s evolution to become momentum-driven, rather than energy driven, drastically decreasing the winds power to disperse its surroundings. In Chapter 2 we lay out the details of this theory, examine how the internal structure of the wind-driven bubble changes in this scenario, and show how such a theory would explain several outstanding observational mysteries. In Chapter 3, we validate this picture with a large suite of three-dimensional, hydrodynamic simulations. In Chapter 4 we test this theory in the context of self-gravitating, self-consistently star forming clouds and show that turbulent cooling is indeed the dominant mechanism for the removal of stellar wind energy. Finally, in Chapter 5 we present the final work of this thesis, where we investigate the effects of background magnetic fields and photo-ionized gas on this picture for stellar wind-driven bubble evolution before reviewing the prospects for future work in Chapter 6.