Planck2013 results. XX. Cosmology from Sunyaev–Zeldovich cluster counts

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 σ 8 and matter density parameter Ω m in a flat ΛCDM 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 σ 8 = 0.75 ± 0.03, Ω m = 0.29 ± 0.02, and σ 8 (Ω m /0.27) 0.3 = 0.764 ± 0.025. The value of σ 8 is degenerate with the mass bias; if the latter is fixed to a value of 20% (the central value from numerical simulations) we find σ 8 (Ω m /0.27) 0.3 = 0.78 ± 0.01 and a tighter one-dimensional range σ 8 = 0.77 ± 0.02. We find that the larger values of σ 8 and Ω m 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 ΛCDM 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.

Constraints on the coupling between dark energy and dark matter from CMB data

“…allowed regions in the (σ8, H0) plane for different models: ΛCDM+νs (gray), MOD1+νs (red) and MOD2+νs (blue), obtained with the full data combination considered here ("ALL"). The vertical green band denotes the interval H0 = 70.6 ± 3.3 Km s −1 Mpc −1 [67] (GE), while the horizontal dark yellow band stands for σ8 = 0.75 ± 0.03 [60] (SZ).…”

A search for sterile neutrinos with the latest cosmological observations

“…However, it has been found that several important astrophysical observations are inconsistent with the Planck observation (based on the CDM cosmology), to some extent. For example, the fit results of the six-parameter a e-mail: zhangxin@mail.neu.edu.cn base CDM model based on the Planck+WP+highL data [11] are in tension with the direct measurement of the Hubble constant [12], the Planck Sunyaev-Zeldovich clusters counts [13], and the cosmic shear measurement of CFHTLenS survey [14].…”

Spherical collapse inνΛCDM

“…The neutrino-induced suppression to the matter power spectrum scales primarily with i m νi and current bounds on the sum of the neutrino masses from cosmological datasets are i m νi ∼ < 0.2eV − 1eV (see e.g. [1][2][3][4] for CMB constraints, [7][8][9][10][11][12][13][14][15][16] for constraints from galaxy and Lyman-alpha forest surveys, and [17][18][19][20][21][22] for constraints from the abundance of galaxy clusters).…”