Abstract

Stars are born from the gravitational collapse of molecular clouds, which are the coldest, densest regions of the interstellar medium (ISM). The primary drivers of ionization in molecular clouds are cosmic rays (CRs), charged particles accelerated to relativistic velocities by high energy shocks. Despite their potential impacts on gas dynamics and chemistry, no previous simulations of star cluster formation have included explicit CR transport to date. CRs could have a significant impact on the star formation properties of the cloud such as the SFE (star formation efficiency) and initial mass function (IMF).

In this defense, I present results from two projects where I conducted  the first numerical simulations following the collapse of molecular clouds and the subsequent star formation including CR transport. These simulations used the STAR FORmation in Gaseous Environments (STARFORGE) framework implemented in the GIZMO code. In the first project, I simulated 2000 solar mass clouds to explore the general impact of CRs on cloud collapse and the SFE. This project also addresses how these results differ in high-CR environments such as the Galactic center and near supernova remnants (SNRs). In the second project, I extended the methods used in these simulations to follow the collapse of 20000 solar mass clouds. These simulations investigate how CRs impact the IMF, including CRs accelerated inside the cloud by stellar wind shocks. Finally, I use my results from both projects to discuss a potential explanation for the elevated CR ionization rates observed in Milky Way molecular clouds. Altogether, my work highlights the importance of including CR transport in future star formation simulations.