Department of Astronomy & Physics
Congratulations to Dr. David Williamson who successfully defended his Ph.D. thesis, "The Origin and Evolution of Cold Gaseous Structures in Galaxies and Galactic Outflows" Supervisor Professor Rob Thacker. Committee: Professors Marcin Sawicki, Bob Deupree, and Hugo Martel (Universite Laval).
David's thesis examines the formation and evolution cold gaseous structures in galaxies and galactic outflows in two distinct scenarios. The first investigation details the impact of the collisions between molecular clouds on the overall viscous evolution of galactic disks. Previous analytic estimates suggested the time-scale associated with this process is 1000 Gyr, far in excess of the Hubble time. David showed these calculations are incorrect and numerical results, along with a new analytical approach, show that the viscous time-scale can be shorter than the lifetime of the Universe. The second part of the thesis examines the creation of cold clouds in outflows from modeled Ultra-luminous Infrared Galaxies (ULIRGS). Using adaptive mesh refinement simulations David has shown that 3d simulations can approximately reproduce the key features of absorption lines in these systems, such as line widths. Including sub-grid turbulence models was not found to improve the accuracy of these models and detailed convergence studies will likely be necessary in the future to determine precisely the nature of cold clouds in outflows.