Higher multipoles of the galaxy bispectrum in redshift space

As a generalization of our previous work [Phys. Rev. D 95 (2017) 043528], in which an analytic model for the galaxy bispectrum in redshift space was developed on the basis of the halo approach, we here investigate its higher multipoles that have not been known so far. The redshift-space bispectrum includes the two variables ω and φ for the line-of-sight direction, and the higher multipole bispectra are defined by the coefficients in the expansion of the redshift-space bispectrum using the spherical harmonics. We find 6 new nonvanishing components out of 25 total components up to ℓ=4, in addition to 3 components discussed in the previous work (monopole, quadruple, and hexadecapole of m=0). The characteristic behaviors of the new nonvanishing multipoles are compared with the results of galaxy mock catalogs that match the halo occupation distribution of the Sloan Digital Sky Survey Baryonic Oscillation Spectroscopic Survey low-redshift sample. We find that the multipoles with m≠ 0 are also sensitive to redshift-space distortion (RSD) as well as those with m=0 and thus are key ingredients in the RSD analysis using the galaxy bispectrum. Analytic approximation formulas for these nonzero components are also presented; these are useful for understanding the characteristic behaviors.