From Large-scale Structure To Galaxy Formation

In this thesis, we use the Sloan Digital Sky Survey (SDSS), supplemented by current semi-analytic models of galaxy formation, to study the statistical properties of the spatial and velocity distributions of different classes of galaxies. The thesis consists of seven chapters.The first chapter provides a brief introduction to the relevant background knowledge, including theoretical models of structure formation and galaxy formation, and how to test these models using redshift surveys of galaxies.In Chapter 2, we use the SDSS DR2 to study how clustering depends on galaxy properties. We find that more massive galaxies cluster more strongly than less massive galaxies, with the difference increasing sharply above L^*. Galaxies with redder colours, larger 4000(?) break strengths, higher concentrations and larger surface mass densities cluster more strongly, and the differences are largest on small scales and for low mass galaxies. At fixed stellar mass, the dependence of clustering on g — r and D4000 extends out to physical scales that are significantly larger than those of individual dark matter haloes (> 5h^-1 Mpc), while this large-scale clustering dependence is not seen for the parameters C or μ_*. On small scales (< 1h^-1 Mpc), the amplitude of the correlation function is constant for "young" galaxies with 1.1 4000 < 1.5 and a steeply rising function of age for "older" galaxies with D₄₀₀₀ > 1.5. In contrast, the dependence of the clustering amplitude on concentration on scales less than 1h^-1 Mpc is strongest for disk-dominated galaxies with C < 2.6. This demonstrates that different processes are required to explain environmental trends in the structure and in the star formation history of galaxies.In Chapter 3, we present measurements of the pairwise velocity dispersion (PVD), using the same samples and focusing on the same physical quantities as in Chapter 2. We confirm the 2dFGRS results of Jing & Borner (2004) that the PVD on small scales decreases with increasing luminosity for galaxies fainter than L^*, before increasing again for the most luminous galaxies. We find that galaxies with redder colours and higher D₄₀₀₀, C, and μ_* values have larger PVDs on all scales and at all luminosi-...