Abstract
Galaxy clusters observed through the thermal Sunyaev–Zeldovich (tSZ) effect are a recent cosmological probe. The precision on the cosmological constraints is affected mainly by the current knowledge of cluster physics, which enters the analysis through the scaling relations. Here we aim to study one of the most important sources of systematic uncertainties, the mass bias,b. We have analysed the effects of a mass-redshift dependence, adopting a power-law parametrisation. We applied this parametrisation to the combination of tSZ number counts and power spectrum, finding a hint of redshift dependence that leads to a decreasing value of the mass bias for higher redshift. We tested the robustness of our results for different mass bias calibrations and a discrete redshift dependence. We find our results to be dependent on the clusters sample that we are considering, in particular obtaining an inverse (decreasing) redshift dependence when neglectingz < 0.2 clusters. We analysed the effects of this parametrisation on the combination of cosmic microwave background (CMB) primary anisotropies and tSZ galaxy clusters. We find a preferred constant value of mass bias, having (1 − b) = 0.62 ± 0.05. The corresponding value ofbis too high with respect to weak lensing and numerical simulations estimations. Therefore we conclude that this mass-redshift parametrisation does not help in solving the remaining discrepancy between CMB and tSZ clusters observations.
Highlights
Galaxy clusters are able to track the recent evolution of the large scale structure, describing the matter density field
In a previous paper (Salvati et al 2018) we show that the well known discrepancy on cosmological parameters, in particular on σ8, obtained from cosmic microwave background radiation (CMB) primary anisotropies and thermal Sunyaev–Zeldovich (tSZ) observations (Planck Collaboration XX 2014; Planck Collaboration XXII 2016; Planck Collaboration XXIV 2016) is substantially reduced, thanks to the lower value of the optical depth provided by Planck Collaboration XLVI (2016)
We report the results obtained for the mass-redshift parametrisation of the mass bias
Summary
Galaxy clusters are able to track the recent evolution of the large scale structure, describing the matter density field. We have introduced uncertainties related to the calibration of the scaling relations between the survey observables and the real mass of the cluster. These relations are needed to extract cosmological information. In order to quantify this bias, we use weak lensing (WL) mass reconstructions, which are supposed to provide an unbiased estimate of the true mass of the cluster, though with a larger scatter – see for example the discussion in Mahdavi et al (2008, 2013), Meneghetti et al (2010), Zhang et al (2010), Hoekstra et al (2015), Smith et al (2016)
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