CMB at small scales: Cosmology from tSZ power spectrum

Marian Douspis,Adélie Gorce,Nabila Aghanim,Laura Salvati,M De Petris,A Ferragamo,F Mayet

doi:10.1051/epjconf/202225700014

Abstract

Small scale CMB angular power spectrum contains not only primordial CMB information but also many contaminants coming from secondary anisotropies. Most of the latter depend on the cosmological model but are often marginalised over. We propose a new analysis of the SPT data focusing on the cosmological contribution of the thermal Sunyaev Zel’dovich (tSZ) effect. We model the tSZ angular spectrum with the halo model and train a random forest algorithm to speed up its computation. We show that using the cosmological information of the tSZ on top of the primordial CMB one contained in SPT data bring more constraints on cosmological parameters. We also combine for the first time Planck tSZ angular power spectrum with SPT ones to put further constraints. This proof of concept study shows how much a proper modelling of the foregrounds in the cosmological analyses is needed.

Highlights

The thermal SZ e↵ect [1] is a good tracer of the hot gas in the Universe, and is often use to detect or characterise clusters of galaxy
Frequency maps observed in the millimetre range contain the sum of many signals coming form the last scattering surface and from all gravitational and electromagnetic e↵ects along the line of sight
As expected, substituting the template by our Random Forest (RF) thermal Sunyaev Zel’dovich (tSZ) power spectrum allows to exploit the full cosmological information, and the constraints are largely tightened with a factor roughly two of improvement

Summary

Introduction

The thermal SZ e↵ect [1] is a good tracer of the hot gas in the Universe, and is often use to detect or characterise clusters of galaxy. It is a secondary anisotropy which contaminates CMB data and analyses. Frequency maps observed in the millimetre range contain the sum of many signals coming form the last scattering surface (primordial CMB) and from all gravitational and electromagnetic e↵ects along the line of sight (one of which is the tSZ). Using an adapted component separation method, it is possible to retrieve the tSZ e↵ect from several frequency map and so create a map tracing the hot gas [2, 3]. From the Planck tSZ map, the angular power spectrum can be estimated and further used to put constraints on the cosmological parameters (eg. [5])

Objectives

Results

Conclusion