We present a measurement of the angular bispectrum of the millimeter-wave sky in observing bands centered at roughly 95 , 150 , and 220 GHz , on angular scales of 1 ^ { \prime } \lesssim \theta \lesssim 10 ^ { \prime } ( multipole number 1000 \lesssim l \lesssim \num { 10000 } ) .
At these frequencies and angular scales , the main contributions to the bispectrum are expected to be the thermal Sunyaev-Zel ’ dovich ( tSZ ) effect and emission from extragalactic sources , predominantly dusty , star-forming galaxies ( DSFGs ) and active galactic nuclei .
We measure the bispectrum in 800 deg ^ { 2 } of three-band South Pole Telescope data , and we use a multi-frequency fitting procedure to separate the bispectrum of the tSZ effect from the extragalactic source contribution .
We simultaneously detect the bispectrum of the tSZ effect at > 10 \sigma , the unclustered component of the extragalactic source bispectrum at > 6 \sigma in each frequency band , and the bispectrum due to the clustering of DSFGs—i.e. , the clustered cosmic infrared background ( CIB ) bispectrum—at > 5 \sigma .
This is the first reported detection of the clustered CIB bispectrum .
We use the measured tSZ bispectrum amplitude , compared to theoretical predictions , to constrain the normalization of the matter power spectrum to be \sigma _ { 8 } = 0.786 \pm 0.031 and to predict the amplitude of the tSZ power spectrum .
This prediction improves our ability to separate the thermal and kinematic contributions to the total SZ power spectrum .
The addition of bispectrum data improves our constraint on the tSZ power spectrum amplitude by a factor of two compared to power spectrum measurements alone and provides the first evidence of a nonzero kinematic SZ ( kSZ ) power spectrum , with a derived constraint on the kSZ amplitude at l = 3000 of A _ { \mathrm { \tiny { kSZ } } } = 2.9 \pm 1.5 \mu \mathrm { K } ^ { 2 } .