Atacama Cosmology Telescope: A measurement of the thermal Sunyaev-Zel'dovich effect using the skewness of the CMB temperature distribution

We present a detection of the unnormalized skewness <(T) over tilde (3)((n) over cap)> 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) over tilde (3)((n) over cap)> = -31 +/- 6 mu K-3 (Gaussian statistics assumed) or +/- 14 mu K-3 ( including non- Gaussian corrections) 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. DOI: 10.1103/PhysRevD.86.122005