Cosmological constraints from moments of the thermal Sunyaev-Zel’dovich effect

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. 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 ${\ensuremath{\sigma}}_{8}$ 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., ${\ensuremath{\sigma}}_{8}$) yet remains sensitive to the astrophysics of intracluster gas (in particular, to the gas fraction in low-mass clusters). Constraining the intracluster medium 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 $\ensuremath{\lesssim}1%$ constraint on ${\ensuremath{\sigma}}_{8}$ and a $1\ensuremath{\sigma}$ error on the sum of the neutrino masses that is comparable to the existing lower bound from oscillation measurements.