Large-Scale Structure Tests of Cosmological Models
Year: 2015
Type: dissertation
Abstract: We investigate the use of $N$-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 $\Lambda$ Cold Dark Matter ($\Lambda$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 $\Lambda$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, $\xi(s)$, of the Sloan Digital Sky Survey (SDSS) Seventh Data Release (DR7) MAIN galaxy catalogue, and fit this to both the $\Lambda$CDM model and the neutrino model. assuming a $\Lambda$CDM cosmology, we obtain a best-fit value for the spherically averaged distance to redshift $z~=~015$, given as $D_V(0.15)~= \left(627~\pm~61\mathrm{Mpc}\right)\left(\frac{r_{s}}{r_{s,fid}}\right)$. 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 $\Omega_m~=~1$ 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.
Author: R. W. F. Johnson
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W263658316