paper

Planck 2013 results. XX. Cosmology from Sunyaev-Zeldovich cluster counts

arXiv:1303.5080 · doi:10.1051/0004-6361/201321521

Abstract

We present constraints on cosmological parameters using number counts as a function of redshift for a sub-sample of 189 galaxy clusters from the Planck SZ (PSZ) catalogue. The PSZ is selected through the signature of the Sunyaev--Zeldovich (SZ) effect, and the sub-sample used here has a signal-to-noise threshold of seven, with each object confirmed as a cluster and all but one with a redshift estimate. We discuss the completeness of the sample and our construction of a likelihood analysis. Using a relation between mass and SZ signal calibrated to X-ray measurements, we derive constraints on the power spectrum amplitude and matter density parameter in a flat CDM model. We test the robustness of our estimates and find that possible biases in the -- relation and the halo mass function are larger than the statistical uncertainties from the cluster sample. Assuming the X-ray determined mass to be biased low relative to the true mass by between zero and 30%, motivated by comparison of the observed mass scaling relations to those from a set of numerical simulations, we find that , , and . The value of is degenerate with the mass bias; if the latter is fixed to a value of 20% we find and a tighter one-dimensional range . We find that the larger values of and preferred by Planck's measurements of the primary CMB anisotropies can be accommodated by a mass bias of about 40%. Alternatively, consistency with the primary CMB constraints can be achieved by inclusion of processes that suppress power on small scales relative to the CDM model, such as a component of massive neutrinos (abridged).

20 pages, accepted for publication by A&A

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