Disentangling non-Gaussianity, bias and GR effects in the galaxy distribution

TL;DR

This paper emphasizes the importance of correctly modeling GR effects and bias in galaxy power spectra to accurately detect primordial non-Gaussianity, demonstrating that improper definitions can mimic signals but are distinguishable through their scale and redshift dependence.

Contribution

It introduces the first consistent GR calculation of galaxy power spectra including bias, enabling better separation of non-Gaussianity from GR effects in future surveys.

Findings

Incorrect bias definitions can mimic non-Gaussianity signals

GR corrections and bias ambiguities have different scale and redshift dependencies

Proper modeling allows disentangling primordial non-Gaussianity from GR effects

Abstract

Local non-Gaussianity, parametrized by $f_{\rm NL}$, introduces a scale-dependent bias that is strongest at large scales, precisely where General Relativistic (GR) effects also become significant. With future data, it should be possible to constrain $f_{\rm NL} = {\cal O}(1)$ with high redshift surveys. GR corrections to the power spectrum and ambiguities in the gauge used to define bias introduce effects similar to $f_{\rm NL}= {\cal O}(1)$, so it is essential to disentangle these effects. For the first time in studies of primordial non-Gaussianity, we include the consistent GR calculation of galaxy power spectra, highlighting the importance of a proper definition of bias. We present observable power spectra with and without GR corrections, showing that an incorrect definition of bias can mimic non-Gaussianity. However, these effects can be distinguished by their different redshift and scale dependence, so as to extract the true primordial non-Gaussianity.