June 18, 1998
We investigate the clustering of high redshift galaxies in five variants of the cold dark matter (CDM) scenario, using hydrodynamic cosmological simulations that resolve the formation of systems with circular velocities $v_c \geq 100 \kms$ ($\Omega=1$) or $v_c \geq 70 \kms$ ($\Omega=0.4$). Although the five models differ in their cosmological parameters and in the shapes and amplitudes of their mass power spectra, they predict remarkably similar galaxy clustering at $z=2$, 3, and 4. The galaxy correlation functions show almost no evolution over this redshift range, even though the mass correlation functions grow steadily in time. Despite the fairly low circular velocity threshold of the simulations, the high redshift galaxies are usually highly biased tracers of the underlying mass distribution; the bias factor evolves with redshift and varies from model to model. Predicted correlation lengths for the resolved galaxy population are $2-3\hmpc$ (comoving) at $z=3$. More massive galaxies tend to be more strongly clustered. These CDM models have no difficulty in explaining the strong observed clustering of Lyman-break galaxies, and some may even predict excessive clustering. Because the effects of bias obscure differences in mass clustering, it appears that Lyman-break galaxy clustering will not be a good test of cosmological models but will instead provide a tool for constraining the physics of galaxy formation.
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September 2, 1997
We present an analysis of the clustering evolution of dark matter in four cold dark matter (CDM) cosmologies. We use a suite of high resolution, 17-million particle, N-body simulations which sample volumes large enough to give clustering statistics with unprecedented accuracy. We investigate both a flat and an open model with Omega_0=0.3, and two models with Omega=1, one with the standard CDM power spectrum and the other with the same power spectrum as the Omega_0=0.3 models....
March 17, 1998
We calculate the statistical clustering of Lyman-break galaxies predicted in a selection of currently-fashionable structure formation scenarios. These models are all based on the cold dark matter model, but vary in the amount of dark matter, the initial perturbation spectrum, the background cosmology and in the presence or absence of a cosmological constant term. If Lyman-break galaxies form as a result of hierarchical merging, the amplitude of clustering depends quite sensit...
July 20, 2006
I review recent progress in understanding and modeling galaxy clustering in cosmological simulations, with emphasis on models based on high-resolution dissipationless simulations. During the last decade, significant advances in our understanding of abundance and clustering of dark matter halos allowed construction of accurate, quantitative models of galaxy clustering both in linear and non-linear regimes. Results of several recent studies show that dissipationless simulations...
March 23, 1999
We have used a combination of high resolution cosmological N-body simulations and semi-analytic modelling of galaxy formation to investigate the processes that determine the spatial distribution of galaxies in cold dark matter (CDM) models. The galaxy distribution depends sensitively on the efficiency with which galaxies form in halos of different mass. In small mass halos, galaxy formation is inhibited by the reheating of cooled gas by feedback processes, whereas in large ma...
October 9, 1997
We perform a detailed analysis of the statistical significance of a concentration of Lyman break galaxies at $z \sim 3$ recently discovered by Steidel et al. (1997), using a series of N-body simulations with $N=256^3$ particles in a $(100\himpc)^3$ comoving box. While the observed number density of Lyman break galaxies at $z\sim3$ implies that they correspond to systems with dark matter halos of $\simlt 10^{12}M_\odot$, the resulting clustering of such objects on average is n...
May 13, 1999
We discuss early results from the first large N-body/hydrodynamical simulation to resolve the formation of galaxies in a cold dark matter universe. The simulation follows the formation of galaxies by gas cooling within dark halos of mass a few times $10^{11}\Msun$ and above, in a flat universe with a positive cosmological constant. Over 2200 galaxies form in our simulated volume of $(100 \Mpc)^3$. Assigning luminosities to the model galaxies using a spectral population synthe...
December 16, 2002
We investigate galaxy clustering and galaxy-mass correlations in the LCDM cosmological model using a large volume SPH simulation. For the most part, the predicted biases between galaxies and dark matter lead to good agreement with current observations, including: (1) a nearly constant comoving correlation length from z=3 to z=0 for mass-selected galaxy samples of constant comoving space density; (2) an rms bias factor b~1 at z=0; (3) a scale-dependent bias on small scales tha...
October 20, 1999
We investigate the clustering properties of high-redshift galaxies within three competing scenarios for assigning luminous galaxies to dark matter halos from N-body simulations: a one galaxy per massive halo model, a quiescent star formation model, and a collisional starburst model. We compare these models to observations of Lyman-Break galaxies at z~3$ With current data and the simple statistic used here, one cannot rule out any of these models, but we see potential for find...
June 2, 1999
We have simulated the growth of structure in two 100 Mpc boxes for LCDM and SCDM universes. These N-body/SPH simulations include a gaseous component which is able to cool radiatively. A fraction of the gas cools into cold dense objects which we identify as galaxies. In this article we give a preliminary analysis of the clustering behaviour of these galaxies concentrating on the LCDM model. We find a galaxy correlation function which is very close to a power law and which evol...
March 18, 1997
We use a semi-analytic model of galaxy formation in hierarchical clustering theories to interpret recent data on galaxy formation and evolution, focussing primarily on the recently discovered population of Lyman-break galaxies at $z\simeq 3$. For a variety of cold dark matter (CDM) cosmologies we construct mock galaxy catalogues subject to identical selection criteria to those applied to the real data. We find that the expected number of Lyman-break galaxies is very sensitive...