Abstract
ABSTRACT We develop a Bayesian method of analysing Sunyaev–Zel’dovich measurements of galaxy clusters obtained from the Arcminute Microkelvin Imager (AMI) radio interferometer system and from the Planck satellite, using a joint likelihood function for the data from both instruments. Our method is applicable to any combination of Planck data with interferometric data from one or more arrays. We apply the analysis to simulated clusters and find that when the cluster pressure profile is known a priori, the joint data set provides precise and accurate constraints on the cluster parameters, removing the need for external information to reduce the parameter degeneracy. When the pressure profile deviates from that assumed for the fit, the constraints become biased. Allowing the pressure profile shape parameters to vary in the analysis allows an unbiased recovery of the integrated cluster signal and produces constraints on some shape parameters, depending on the angular size of the cluster. When applied to real data from Planck-detected cluster PSZ2 G063.80+11.42, our method resolves the discrepancy between the AMI and Planck Y-estimates and usefully constrains the gas pressure profile shape parameters at intermediate and large radii.
Highlights
With the advent of large Sunyaev–Zel’dovich (SZ) effect surveys carried out by instruments such as Planck (Planck Collaboration XXVII 2016), the Atacama Cosmology Telescope (Hilton et al 2018), and the South Pole Telescope (Bleem et al 2015), SZ observations have the potential to become a powerful tool for constraining, for example, cosmological properties via cluster number counts
They showed that the discrepancies between the cluster parameters as constrained by Arcminute Microkelvin Imager (AMI) and Planck could be explained by the cluster gas pressure profile deviating from the profile assumed for analysis
AMI consists of two arrays: the Small Array (SA), optimized for viewing arcminute-scale features, having an angular resolution of ≈3 arcmin and sensitivity to structures up to ≈10 arcmin in scale; and the Large Array (LA), with angular resolution of ≈30 arcsec, which is insensitive to SA angular scales and is used to characterize and subtract confusing radio-sources
Summary
With the advent of large Sunyaev–Zel’dovich (SZ) effect surveys carried out by instruments such as Planck (Planck Collaboration XXVII 2016), the Atacama Cosmology Telescope (Hilton et al 2018), and the South Pole Telescope (Bleem et al 2015), SZ observations have the potential to become a powerful tool for constraining, for example, cosmological properties via cluster number counts. The AMI observations were shown to be sensitive to this effect when attempting to constrain the total integrated Comptony parameter due to missing angular scales It was noted in P15 that the combination of the two instruments would be powerful for investigating the gas pressure profiles of the clusters due to the complementary angular scales measured. This work joins a growing body of analysis combining SZ data from different instruments, sensitive to different angular scales Recent works such as Sayers et al (2016), Ruppin et al (2017), and Di Mascolo, Churazov & Mroczkowski (2018) all combine Planck Modified Internal Linear Combination Algorithm (MILCA; Planck Collaboration XXII 2016) y-maps with SZ data from other instruments to jointly fit the gas pressure profile, while Romero et al (2018) use a Planck-derived prior on the integrated Comptony parameter; to our knowledge, this is the first time that Planck frequency maps (rather than y-maps) have been jointly analysed with other SZ data.
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