Parameter constraints for flat cosmologies from CMB and 2dFGRS power spectra
Abstract
We constrain flat cosmological models with a joint likelihood analysis of a new compilation of data from the cosmic microwave background (CMB) and from the 2dF Galaxy Redshift Survey (2dFGRS). Fitting the CMB alone yields a known degeneracy between the Hubble constant h and the matter density Omega_m, which arises mainly from preserving the location of the peaks in the angular power spectrum. This `horizon-angle degeneracy' is considered in some detail and shown to follow a simple relation Omega_m h^{3.4} = constant. Adding the 2dFGRS power spectrum constrains Omega_m h and breaks the degeneracy. If tensor anisotropies are assumed to be negligible, we obtain values for the Hubble constant h=0.665 +/- 0.047, the matter density Omega_m=0.313 +/- 0.055, and the physical CDM and baryon densities Omega_c h^2 = 0.115 +/- 0.009, Omega_b h^2 = 0.022 +/- 0.002 (standard rms errors). Including a possible tensor component causes very little change to these figures; we set a upper limit to the tensor-to-scalar ratio of r<0.7 at 95% confidence. We then show how these data can be used to constrain the equation of state of the vacuum, and find w<-0.52 at 95% confidence. The preferred cosmological model is thus very well specified, and we discuss the precision with which future CMB data can be predicted, given the model assumptions. The 2dFGRS power-spectrum data and covariance matrix, and the CMB data compilation used here, are available from http://www.roe.ac.uk/~wjp/
Cite
@article{arxiv.astro-ph/0206256,
title = {Parameter constraints for flat cosmologies from CMB and 2dFGRS power spectra},
author = {Will J. Percival and Will Sutherland and John A. Peacock and Carlton M. Baugh and Joss Bland-Hawthorn and Terry Bridges and Russell Cannon and Shaun Cole and Matthew Colless and Chris Collins and Warrick Couch and Gavin Dalton and Roberto De Propris and Simon P. Driver and George Efstathiou and Richard S. Ellis and Carlos S. Frenk and Karl Glazebrook and Carole Jackson and Ofer Lahav and Ian Lewis and Stuart Lumsden and Steve Maddox and Stephen Moody and Peder Norberg and Bruce A. Peterson and Keith Taylor},
journal= {arXiv preprint arXiv:astro-ph/0206256},
year = {2011}
}
Comments
14 pages, 7 figures, minor revision, accepted for publication in MNRAS