The Hydrodynamic stripping of spheroids and disks

This thesis presents numerical simulations of the ablation of galaxies and stellar disks. A sub-grid turbulence model is used to improve the accuracy of the results. Firstly simulations of galactic ram pressure stripping are presented. A spherically symmetric galactic halo is subjected to a wind of a number of different Mach numbers, both with and without the turbulence model. The initial, instantaneous stripping is unaffected by the use of the turbulence model. The turbulence model leads to significantly greater levels of long term ablation, which is more consistent with what simple analytic calculations indicate, showing that the continual Kelvin-Helmholtz stripping plays a significant role in the ram pressure stripping and this is hidden by the finite resolution of simulations without turbulence models.

Secondly the turbulence model is applied to galactic disk simulations. In high Mach number (∼ 15) rotating disks the turbulence generated from the internal stresses in the disk causes it to become unstable and erroneously expand in the z direction. This is not the case for lower Mach number disks, such as dwarf disk galaxies. Further developments are needed in turbulence modelling if disk galaxies are to be simulated in this way.

Finally inviscid simulations of the interaction of a supernova remnant on a stellar disk are presented. The supernova remnant is simulated hydrodynamically as opposed to using analytical approximations which represents an improvement on previous models. A number of inclination angles of the disk are considered which is not possible with previous two dimensional simulations. Mass loss rates are calculated and compared to other competing processes. Similarly to disk galaxies, the inclination angle only has a large effect on the evolution when the disk is close to edge on. Edge on disks develop an asymmetry when the ablation period is less than the rotation period of the disk. Contamination of the disk with supernova material is also investigate and is found to be low (about one part in 200, 000 in the highest case), consistent with previous results.