The Atacama Cosmology Telescope: A Measurement of the Thermal Sunyaev-Zel'dovich Effect Using the Skewness of the CMB Temperature Distribution

TL;DR

This paper reports a 5-sigma detection of the skewness in CMB temperature maps caused by the thermal Sunyaev-Zel'dovich effect, providing new constraints on cosmological parameters like sigma_8.

Contribution

It introduces a novel measurement of the skewness of CMB temperature distribution to probe the tSZ effect and derive cosmological constraints, demonstrating the utility of non-Gaussianity analysis.

Findings

Detected <T^3> = -31 ± 6 μK^3 with 5-sigma significance.

Inferred sigma_8 = 0.79 +0.03 -0.03 from skewness measurement.

Showed non-Gaussianity measurements can effectively characterize the tSZ effect.

Abstract

We present a detection of the unnormalized skewness <T^3> induced by the thermal Sunyaev-Zel'dovich (tSZ) effect in filtered Atacama Cosmology Telescope (ACT) 148 GHz cosmic microwave background temperature maps. Contamination due to infrared and radio sources is minimized by template subtraction of resolved sources and by constructing a mask using outlying values in the 218 GHz (tSZ-null) ACT maps. We measure <T^3>= -31 +- 6 \mu K^3 (measurement error only) or +- 14 \mu K^3 (including cosmic variance error) in the filtered ACT data, a 5-sigma detection. We show that the skewness is a sensitive probe of sigma_8, and use analytic calculations and tSZ simulations to obtain cosmological constraints from this measurement. From this signal alone we infer a value of sigma_8= 0.79 +0.03 -0.03 (68 % C.L.) +0.06 -0.06 (95 % C.L.). Our results demonstrate that measurements of non-Gaussianity can be a useful method for characterizing the tSZ effect and extracting the underlying cosmological information.