The shocking stars : numerical modelling of stellar feedback in giant molecular clouds

From the scales of molecular clouds to galaxies, feedback from massive stars is crucial for understanding the star formation process. Type II supernovae are deemed one of the biggest source of energy and momentum in the interstellar medium. They limit the cold gas reservoir by dispersing clouds and launching galactic outflows. Meanwhile, pre-supernova feedback, such as ionizing radiation, may modify the environment of supernova progenitors by creating bubbles and channels. These structures largely determine the dynamical impact of feedback. The first half of this thesis describes the numerical methods I used for studying photoionization in star-forming regions. We employed the smoothed particle hydrodynamics (SPH) technique to simulate the molecular clouds. I present our tree-based radiation hydrodynamics scheme that couples SPH to Monte Carlo radiative transfer code for modelling H ɪɪ regions. This scheme also involves novel algorithms for setting up pseudo-SPH particles, and for computing photoionization heating and cooling. The second half of the thesis investigates how feedback energy leaves the cloud preferentially through the paths of least resistance, and what it implies about our current supernova sub-grid models. I devised an analytical model to describe supernovae that are partially confined in a porous feedback-driven cavity. The analytical model is verified with simulations of idealized clouds with simplified geometries, and with turbulent molecular clouds in realistic environments. I compared them against supernova blasts in homogeneous environments which are often used to formulate the 1-D feedback prescriptions. I showed that semi-confined supernovae can sustain a relatively higher kinematic input in regions closer to the progenitor, and I argue for the importance of incorporating channelling effects into feedback models.