Impact of the mean pressure profile of galaxy clusters on the cosmological constraints from the $Planck$ tSZ power spectrum
Résumé
Cosmological analyses based on surveys of galaxy clusters observed through the Sunyaev–Zel’dovich (SZ) effect strongly rely on the mean pressure profile of the cluster population. A tension is currently observed between the cosmological constraints obtained from the analyses of the CMB primary anisotropies and those from cluster abundance in SZ surveys. This discrepancy may be explained by a wrong estimate of the hydrostatic bias parameter that links the hydrostatic mass to the true mass of galaxy clusters. However, a variation of both the amplitude and the shape of the mean pressure profile could also explain part of this tension. We analyse the effects of a modification of this profile on the constraints of the σ_8 and Ω_m parameters through the analysis of the SZ power spectrum measured by the Planck collaboration. We choose two mean pressure profiles that are respectively lower and higher than the one obtained from the observation of nearby clusters by Planck. The selection of the parameters of these two profiles is based on the current estimates of the pressure and gas mass fraction profile distributions at low redshift. The cosmological parameters found for these two profiles are significantly different from the ones obtained with the Planck pressure profile. We conclude that an |${\sim }15{{\ \rm per\ cent}}$| decrease of the amplitude of the mean normalized pressure profile would alleviate the tension observed between the constraints of σ_8 and Ω_m from the CMB and cluster analyses without requiring extreme values of the mass bias parameter.