Abstracts Physics

A Study into the Formation of Coherent Pre-Steller Cores in Molecular Clouds

by Dan Khac Le

This dissertation is a collection of our research on star forming cores. We used tracer particles to record time dependent information on the gases that make up these cores. From these information we deduced core characteristics. We found that as time progresses, cores approach a state of coherency as defined by (Goodman et al. 1998b) and Larson (1995). At a core's coherency phase, it also forms an ρ ∝ r−2 density radial profile. This is an indication of symmetric spherical collapse as described by Larson (1969), Penston (1969a) and Shu (1977). Spherically symmetric happens because the effects of magnetic fields are dampened by that of the gas, meaning that magnetic fields have little effect on a coherent core's dynamics. We also found evidence that cores accretes mass after fragmentation occurs, and a coherent core has formed. This evidence was discovered by looking at density vs time plots of our cores, as well as from studying the density probability distribution function (PDF) of our molecular clouds. Using our density (PDF) we also analytically derived an expression for the star formation rate. Finally studying the gravitational binding energy of our cores, we found that coherent cores has a radius around 1 × 10−2 pc, is gravitationally bounded, and has a potential that is spherical. This add credence to the idea that our cores are going through spherically symmetric collapse at the point of coherency. Finally, We found that the gravitational binding energy outside of the coherent regions of our cores is greater than that of a spherical core. This trend is universal to most cores, including the most isolated ones. This indicates that a global potential, or semi-global potential, might be the agent of accretion. A Dissertation submitted to the Department of Physics in partial fulfillment of the requirements for the degree of Doctor of Philosophy. June 24, 2022. David Collins, Professor Directing Dissertation; Ettore Aldrovandi, University Representative; Jeremiah Murphy, Committee Member; Jorge Piekarewicz, Committee Member; Kevin Huffenberger, Committee Member.