### 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 M and SZ signal Y
calibrated to X-ray measurements, we derive constraints
on the power spectrum amplitude s8 and matter density
parameter Om in a flat ?CDM model. We test the robustness
of our estimates and find that possible biases in the Y-M
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 s8 = 0.75 ± 0.03, Om = 0.29 ± 0.02, and
s8(Om/0.27)0.3 = 0.764 ± 0.025. The value of s8 is
degenerate with the mass bias; if the latter is fixed to
a value of 20% (the central value from numerical
simulations) we find s8(Om/0.27)0.3 = 0.78 ± 0.01 and a
tighter one-dimensional range s8 = 0.77 ± 0.02. We find
that the larger values of s8 and Om 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. We place our results in
the context of other determinations of cosmological
parameters, and discuss issues that need to be resolved
in order to make further progress in this field.

Original language | English |
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Article number | A20 |

Number of pages | 20 |

Journal | Astronomy and Astrophysics |

Volume | 571 |

DOIs | |

Publication status | Published - 2014 |

MoE publication type | A1 Journal article-refereed |

### Keywords

- cosmological parameters
- galaxies
- universe

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## Cite this

Tuovinen, J., & Planck Collaboration (2014). Planck 2013 results: XX. Cosmology from Synyaev-Zeldovich cluster counts.

*Astronomy and Astrophysics*,*571*, [A20]. https://doi.org/10.1051/0004-6361/201321521