Clustering of galaxies in a hierarchical universe - II. Evolution to high redshift

In hierarchical cosmologies the evolution of galaxy clustering depends both on cosmological quantities such as Omega, Lambda and P(k), which determine how collapsed structures - dark matter haloes - form and evolve, and on th e physical processes - cooling, star formation, radiative and hydrodynamic feedback - which drive the formation of galaxies within these merging haloe s, In this paper we combine dissipationless cosmological N-body simulations and semianalytic models of galaxy formation in order to study how these tw o aspects interact. We focus on the differences in clustering predicted for galaxies of differing luminosity, colour, morphology and star formation ra te, and on what these differences can teach us about the galaxy formation p rocess. We show that a 'dip' in the amplitude of galaxy correlations betwee n z = 0 and z = 1 can be an important diagnostic. Such a dip occurs in low- density CDM models, because structure forms early, and dark matter haloes o f mass similar to 10(12) M-., containing galaxies with luminosities similar to L-*, are unbiased tracers of the dark matter over this redshift range; their clustering amplitude then evolves similarly to that of the dark matte r. At higher redshifts, bright galaxies become strongly biased and the clus tering amplitude increases again. In high density models, structure forms l ate, and bias evolves much more rapidly. As a result, the clustering amplit ude of L-* galaxies remains constant from z = 0 to z = 1. The strength of t hese effects is sensitive to sample selection. The dip becomes weaker for g alaxies with lower star formation rates, redder colours, higher luminositie s and earlier morphological types. We explain why this is the case, and how it is related to the variation with redshift of the abundance and environm ent of the observed galaxies. We also show that the relative peculiar veloc ities of galaxies are biased low in our models, but that this effect is nev er very strong. Studies of clustering evolution as a function of galaxy pro perties should place strong constraints on models of galaxy formation and e volution.