Orbital decay in triaxial shaped dark matter haloes
thesisposted on 15.12.2014, 10:40 by Jalpesh Sachania
In cosmological simulations of structure formation of the universe, the dark matter halos in which galaxies are embedded in, are triaxial in shape. Simulations which focus in on galaxies in isolation do not use triaxial dark matter halos but use spherical shaped halos instead, as triaxial equilibrium models are hard to create.;Using a new method of creating initial conditions, which is able to create triaxial equilibrium models, the effect of using a triaxial halo in simulations of satellite accretion will be studied. In previous studies with a spherical shaped dark matter halo, the initial position of the satellite is unimportant due to the symmetry of the system, however in a triaxial halo this is not the case and the initial position becomes important. A study of the parameter space of the initial position and velocity of a satellite is undertaken and the orbital decay is compared in each case.;The different mergers will also have different effects upon the halo itself as the orbital energy of the satellite is transferred to the halo. The effects of a minor merger onto the halo is investigated and compared to the scenario more commonly used when the halo is spherical.;This study is then extended to find out whether the orbital decay in a triaxial potential, which can differ significantly from that in a spherical halo, can be used to explain the observations of polar ring galaxies and gas discs in elliptical galaxies.