Cosmological Constraints from Moments of the Thermal Sunyaev-Zel'dovich Effect

TL;DR

This paper introduces a novel statistical method using moments of the thermal Sunyaev-Zel'dovich effect to simultaneously constrain cosmological parameters and intracluster medium physics, reducing degeneracies in tSZ measurements.

Contribution

The authors develop a new statistic based on tSZ moments that isolates astrophysical effects from cosmological parameters, enabling improved constraints from tSZ data.

Findings

Higher tSZ moments scale steeply with sigma_8.

The statistic |<T^3>|/<T^2>^1.4 reduces cosmological dependence.

A full-sky Planck-like tSZ map could constrain sigma_8 to below 1%.

Abstract

In this paper, we explain how moments of the thermal Sunyaev-Zel'dovich (tSZ) effect can constrain both cosmological parameters and the astrophysics of the intracluster medium (ICM). As the tSZ signal is strongly non-Gaussian, higher moments of tSZ maps contain useful information. We first calculate the dependence of the tSZ moments on cosmological parameters, finding that higher moments scale more steeply with sigma_8 and are sourced by more massive galaxy clusters. Taking advantage of the different dependence of the variance and skewness on cosmological and astrophysical parameters, we construct a statistic, |<T^3>|/<T^2>^1.4, which cancels much of the dependence on cosmology (i.e., sigma_8) yet remains sensitive to the astrophysics of intracluster gas (in particular, to the gas fraction in low-mass clusters). Constraining the ICM astrophysics using this statistic could break the well-known degeneracy between cosmology and gas physics in tSZ measurements, allowing for tight constraints on cosmological parameters. Although detailed simulations will be needed to fully characterize the accuracy of this technique, we provide a first application to data from the Atacama Cosmology Telescope and the South Pole Telescope. We estimate that a Planck-like full-sky tSZ map could achieve a <1% constraint on sigma_8 and a 1-sigma error on the sum of the neutrino masses that is comparable to the existing lower bound from oscillation measurements.