Bispectrum non-Gaussian Covariance in Redshift Space
arxiv(2024)
摘要
We provide an analytical description of the galaxy bispectrum covariance and
the power spectrum-bispectrum cross-covariance in redshift space that captures
the dominant non-Gaussian contributions. The Gaussian prediction for the
variance of the halo bispectrum monopole significantly underestimates numerical
estimates particularly for squeezed triangles, that is bispectrum triangular
configurations where one side is much smaller than the other two, whereas the
effect is relatively less important when considering the quadrupole. We propose
an expression for the missing non-Gaussian contribution valid in the squeezed
limit that requires an accurate modeling of the bispectrum alone. We validate
our model against the numerical covariance estimated from a large suite of mock
catalogs and find that it accurately predicts the variance as well as the
dominant off-diagonal terms. We also present an expression for the
cross-covariance between power spectrum and bispectrum multipoles and likewise
find it to provide a good description of the numerical results.
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