Probing higher-order primordial non-Gaussianity with galaxy surveys

TL;DR

This paper forecasts how upcoming galaxy surveys like SKA and Euclid can constrain higher-order primordial non-Gaussianity parameters, aiding in testing inflationary models and the consistency inequality.

Contribution

It provides a Fisher matrix analysis showing the complementary strengths of SKA and Euclid in constraining nonlinear parameters of primordial non-Gaussianity.

Findings

SKA is better for constraining τ_NL

Euclid excels in constraining f_NL due to redshift info

Joint analysis can confirm the inflationary consistency inequality for f_NL ≈ 1.5 and τ_NL ≈ 17

Abstract

With a radio continuum galaxy survey by the Square Kilometre Array (SKA), a photometric galaxy survey by Euclid and their combination, we forecast future constraints on primordial non-Gaussianity. We focus on the potential impact of local-type higher-order nonlinear parameters on the parameter estimation and particularly the confirmation of the inflationary consistency inequality. Nonstandard inflationary models, such as multifield models, introduce the scale-dependent stochastic clustering of galaxies on large scales, which is a unique probe of mechanism for generating primordial density fluctuations. Our Fisher matrix analysis indicates that a deep and wide survey provided by SKA is more advantageous to constrain $\tau_{\rm NL}$, while Euclid has a strong constraining power for $f_{\rm NL}$ due to the redshift information, suggesting that the joint analysis between them is quite essential to break the degeneracy between the nonlinear parameters. The combination of the full SKA and Euclid will achieve the precision level needed to confirm the consistency inequality even for $f_{\rm NL}\approx 1.5$ and $\tau_{\rm NL}\approx 17$, though it is still hard for a single survey to confirm it when $f_{\rm NL}\lesssim 2.7$.