An optimal and model-independent measurement of the intracluster pressure profile-I. Methodology and first applications

Abstract

We present a statistically optimal and model-independent method to extract the pressure profile of hot gas in the intracluster medium (ICM). Using the thermal Sunyaev-Zeldovich effect, we constrain the mean pressure profile of the ICM by appropriately considering all primary cosmic microwave background (CMB) and instrumental noise correlations, while using the maximum resolution and sensitivity of all frequency channels. As a first application, we analyse CMB maps of Wilkinson Microwave Anisotropy Probe 9-year data through a study of the Meta- Catalogue of X-ray Detected Clusters of Galaxies.We constrain the universal pressure profile out to 4R500 with 15σ confidence, though our measurements are only significant out to R200. Using a temperature profile constrained from X-ray observations, we measure the mean gas mass fraction out to R200. Within statistical and systematic uncertainties, our constraints are compatible with the cosmic baryon fraction and the expected gas fraction in haloes. While Planck multifrequency CMB data are expected to reduce statistical uncertainties by a factor of ~20, we argue that systematic errors in determining mass of clusters dominate the uncertainty in gas mass fraction measurements at the level of ~20 per cent. © 2013 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society.