# Wide-angle effects in the galaxy bispectrum

## TL;DR

This paper develops a formalism to incorporate wide-angle effects into the galaxy bispectrum analysis, highlighting their potential to mimic primordial non-Gaussian signals and assessing their significance for upcoming large-volume surveys.

## Contribution

It introduces a method to include wide-angle corrections in the 3D galaxy bispectrum, enabling more accurate PNG measurements in future surveys.

## Key findings

- Wide-angle effects can mimic local PNG with f_NL ~ 0.1.
- Dipole effects are detectable in surveys larger than 50 Gpc^3/h^3.
- Wide-angle monopole corrections are negligible for surveys of 8 Gpc^3/h^3 volume.

## Abstract

Primordial non-Gaussianities (PNG) leave unique signatures in the bispectrum of the large-scale structure. With upcoming galaxy surveys set to improve PNG constraints by at least one order of magnitude, it is important to account for any potential contamination. In our work we show how to include wide-angle effects into the 3-dimensional observed galaxy bispectrum. We compute the leading wide-angle corrections to the monopole, finding that they could mimic local PNG with an amplitude of $f_{\rm NL} = \mathcal{O}\left( 0.1 \right)$. We also compute the dipole induced by wide-angle effects, whose amplitude is a few-percent of the flat-sky monopole. We estimate that wide-angle effects in the monopole can be safely neglected for survey volumes of the order of $8~\mathrm{Gpc}^3 h^{-3}$, while the dipole can start being detected from surveys probing volumes larger than $50~\mathrm{Gpc}^3 h^{-3}$. Our formalism can be readily adapted to realistic survey geometries and to include relativistic effects, which may become relevant at high redshifts.