Constraining primordial non-Gaussianity with bispectrum and power spectrum from upcoming optical and radio surveys

Abstract

We forecast constraints on primordial non-Gaussianity (PNG) and bias parameters from measurements of galaxy power spectrum and bispectrum in future radio continuum and optical surveys. In the galaxy bispectrum, we consider a comprehensive list of effects, including the bias expansion for non-Gaussian initial conditions up to second order, redshift space distortions, redshift uncertainties and theoretical errors. These effects are all combined in a single PNG forecast for the first time. Moreover, we improve the bispectrum modelling over previous forecasts, by accounting for trispectrum contributions. All effects have an impact on final predicted bounds, which varies with the type of survey. We find that the bispectrum can lead to improvements up to a factor ∼ 5 over bounds based on the power spectrum alone, leading to significantly better constraints for local-type PNG, with respect to current limits from Planck. Future radio and photometric surveys could obtain a measurement error of σ(f loc NL ) ≈ 0.2. In the case of equilateral PNG, galaxy bispectrum can improve upon present bounds only if significant improvements in the redshift determinations of future, large volume, photometric or radio surveys could be achieved. For orthogonal non-Gaussianity, expected constraints are generally comparable to current ones.

Detecting the relativistic galaxy bispectrum

“…The effect of RSD on these scales is to damp the power -the 'FoG' effect. In order to take account of this, we follow [3,4] and use the simple model of FoG damping,…”

“…The three angles θ ab = cos −1 k a ·k b , are determined by k a ; then µ 2 = µ 1 cos θ 12 + sin θ 1 sin θ 12 cos ϕ is determined when ϕ is given, and µ 3 = −(µ 1 k 1 + µ 2 k 2 )/k 3 . In the standard Newtonian approximation, B g = B gN , the kernels in (1.2) contain the galaxy bias and the redshift-space distortions (RSD) at first and second order [3,10]:…”

Imprints of local lightcone projection effects on the galaxy bispectrum IV: second-order vector and tensor contributions

“…The galaxy bispectrum will help differentiate between cosmological models in future surveys [1][2][3][4][5][6][7][8][9][10], test the equivalence principle on large scales [11], further constrains the modified gravity models [12] and will help constrain primordial non-Gaussianity [13][14][15]. On large scales the bispectrum is affected by relativistic effects, mainly from lightcone projection effects on the observed number density [16][17][18][19][20][21][22][23][24][25].…”

Measuring neutrino masses with large-scale structure: Euclid forecast with controlled theoretical error

“…However, the LSS data analysis is complicated by effects of non-linear clustering, galaxy bias and redshift space distortions. Our ability to fully and yield more robust constraints on cosmological parameters [37][38][39][40][41][42].…”