Cosmological information in the redshiftspace bispectrum
Abstract
We use the Fishermatrix formalism to investigate whether the galaxy bispectrum in redshift space, B, contains additional cosmological information with respect to the power spectrum, P. We focus on a Euclidlike survey and consider cosmological models dominated by dark energy and cold dark matter with Gaussian primordial perturbations. After discussing the phenomenology of redshiftspace distortions for the bispectrum, we derive an expression for the crosscovariance between B and P at leading order in perturbation theory. Our equation generalizes previous results that did not consider binning in the orientation of wavevector triangles with respect to the line of sight. By considering Fourier modes with wavenumber k<0.15 h Mpc^{1}, we find that B and P set similar constraints on the cosmological parameters. Generally, error bars moderately improve when the two probes are combined together. For instance, the joint 68.3 per cent credible region for the parameters that describe a dynamical darkenergy equation of state shrinks by a factor of 2.6 with respect to only using the power spectrum. Regrettably, this improvement is cancelled out when the clustering analysis is combined with priors based on current studies of the cosmic microwave background. In this case, combining B and P does not give any appreciable benefit other than allowing a precise determination of galaxy bias. Finally, we discuss how results depend on the binning strategy for the clustering statistics as well as on the maximum wavenumber. We also show that only considering the bispectrum monopole leads to a significant loss of information.
 Publication:

Monthly Notices of the Royal Astronomical Society
 Pub Date:
 February 2019
 DOI:
 10.1093/mnras/sty3143
 arXiv:
 arXiv:1807.07076
 Bibcode:
 2019MNRAS.483.2078Y
 Keywords:

 cosmology: cosmological parameters;
 cosmology: dark energy;
 cosmology: largescale structure of Universe;
 Astrophysics  Cosmology and Nongalactic Astrophysics
 EPrint:
 24 pages, 15 figures, accepted for publication in MNRAS. Minor changes to match the published version. Includes updated HOD model for Euclid galaxies. Conclusions unchanged