Large-Scale Structure Tests of Cosmological Models

Abstract

We investigate the use of -body simulations and large-scale galaxy clustering in order to test two cosmological models: an Einstein-de Sitter model where neutrinos act as the dominant Hot Dark Matter (HDM) component; and the standard Cold Dark Matter (CDM) model. We investigate the matter power spectra and halo mass functions of the neutrino model, and of an extended model that includes Primordial Magnetic Fields (PMFs), which have the effect of introducing `seeds' into the matter distribution. We find that neither model performs as well as CDM in generating structure, but note that the use of PMFs completely reverses the process of structure formation in the HDM model, allowing it to progress in a bottom-up manner.

We calculate the redshift-space two-point galaxy-galaxy correlation function, , of the Sloan Digital Sky Survey (SDSS) Seventh Data Release (DR7) MAIN galaxy catalogue, and fit this to both the CDM model and the neutrino model. assuming a CDM cosmology, we obtain a best-fit value for the spherically averaged distance to redshift , given as . This is in agreement with recent work, and is our best-fit model to the SDSS DR7 MAIN data. We find that the correlation function from the MAIN galaxies cannot reject an model in a cosmological ruler test, and the and the BAO peak is not pronounced enough to significantly reject a neutrino HDM model. However, the neutrino model is rejected by the non-linear form of the matter power spectrum, even though the magnetic version of the model may form galaxies by the present day.