Abstract
To fully extract cosmological information from nonlinear galaxy distribution in redshift space, it is essential to include higherorder statistics beyond the twopoint correlation function. In this paper,we propose a newdecomposition formalism for computing the anisotropic bispectrum in redshift space and formeasuring it from galaxy samples. Our formalism uses tripolar spherical harmonic decomposition with zero total angular momentum to compress the 3D modes distribution in the redshiftspace bispectrum. This approach preserves three fundamental properties of the Universe  statistical homogeneity, isotropy, and paritysymmetry. allowing us to efficiently separate the anisotropic signal induced by redshiftspace distortions (RSDs) and the AlcockPaczyński (AP) effect from the isotropic bispectrum. The relevant expansion coefficients in terms of the anisotropic signal are reduced to one multipole index L, and the L > 0 modes are induced only by the RSD or AP effects. Our formalism has two advantages: (1) we can make use of Fast Fourier Transforms to measure the bispectrum and (2) it gives a simple expression to correct for the survey geometry, i.e. the survey window function. As a demonstration, we measure the decomposed bispectrum from the Baryon Oscillation Spectroscopic Survey (BOSS) Data Release 12, and, for the first time, present a 14σ detection of the anisotropic bispectrum in the L = 2 mode.
Original language  English 

Pages (fromto)  364384 
Number of pages  21 
Journal  Monthly Notices of the Royal Astronomical Society 
Volume  484 
Issue number  1 
Early online date  30 Nov 2018 
DOIs  
Publication status  Published  1 Mar 2019 
Keywords
 Cosmology: observations
 Cosmology: theory
 Dark matter
 Largescale structure of Universe
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Sugiyama, N. S. (Creator), Saito, S. (Creator), Beutler, F. (Creator) & HeeJong Seo, S. (Creator), Oxford University Press, 1 Mar 2019
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