Structure and Dynamics of ΛCDM Haloes

Abstract

In the standard model (ΛCDM) galaxies form and evolve within underlying dark matter structures which are assumed to have grown hierarchically. As such there should be observational signatures of the merging process in the structure and dynamics of the remnant galaxy. State-of-the-art high-resolution cosmological simulations have been used to explore three such signatures: the abundance of substructure, the spin and shape of haloes, and the orbital content of these haloes.The Millennium Simulation, combined with semi-analytic galaxy catalogues, is used to compare the predicted frequency of bright central satellites to observations of field and lens galaxies. The predicted frequency is largely independent of galaxy type, but is shown to increase with redshift and halo mass. The predicted frequency is found to be lower than that observed in the Compact Lens All Sky Survey, but considerably higher than that observed in the lens sample of the Sloan Lens ACS Survey and in the field galaxies of the Sloan Digital Sky Survey and the Cosmic Evolution Survey. The distributions of the spin and shape of haloes are explored and the roles of baryons and the physical prescriptions of stellar and black hole feedback are investigated. Baryons act to make the haloes more spherical and are shown to have a significant effect on the shape of the dark matter. The shapes of the simulated haloes are in broad agreement with a wide range of observational estimates of elliptical galaxies. Results of spectral analyses of the orbital content of simulations with different feedback prescriptions are presented. Dark matter only haloes are dominated by box orbits in the central region, but the fraction of box orbits is found to decrease when baryons are included. The orbits of the stellar particles are found to be remarkably similar to those of dark matter particles.

Date of Award	1 Aug 2011
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Shude Mao (Supervisor) & Scott Kay (Supervisor)