TY - JOUR

T1 - Non-Gaussianities due to relativistic corrections to the observed galaxy bispectrum

AU - Dio, E. Di

AU - Perrier, H.

AU - Durrer, R.

AU - Marozzi, G.

AU - Dizgah, A. Moradinezhad

AU - Noreña, J.

AU - Riotto, A.

N1 - Funding Information:
We would like to thank R. Maartens and O. Umeh for useful conversations. E.D. is supported by the ERC Starting Grant cosmoIGM and by INFN/PD51 INDARK grant. G.M. wishes to thank CNPq for financial support. A.M. is supported by the Tomalla foundation for Gravity Research for part of this research. J.N. is supported by Proyecto VRIEA-PUCV 039.362/2016. A.R. is supported by the Swiss National Science Foundation (SNSF), project Investigating the Nature of Dark Matter, project number: 200020-159223. Also R.D. and H.P. acknowledge support from the Swiss National Science Foundation.
Publisher Copyright:
© 2017 IOP Publishing Ltd and Sissa Medialab srl.

PY - 2017/3/6

Y1 - 2017/3/6

N2 - High-precision constraints on primordial non-Gaussianity (PNG) will significantly improve our understanding of the physics of the early universe. Among all the subtleties in using large scale structure observables to constrain PNG, accounting for relativistic corrections to the clustering statistics is particularly important for the upcoming galaxy surveys covering progressively larger fraction of the sky. We focus on relativistic projection effects due to the fact that we observe the galaxies through the light that reaches the telescope on perturbed geodesics. These projection effects can give rise to an effective fNL that can be misinterpreted as the primordial non-Gaussianity signal and hence is a systematic to be carefully computed and accounted for in modelling of the bispectrum. We develop the technique to properly account for relativistic effects in terms of purely observable quantities, namely angles and redshifts. We give some examples by applying this approach to a subset of the contributions to the tree-level bispectrum of the observed galaxy number counts calculated within perturbation theory and estimate the corresponding non-Gaussianity parameter, fNL, for the local, equilateral and orthogonal shapes. For the local shape, we also compute the local non-Gaussianity resulting from terms obtained using the consistency relation for observed number counts. Our goal here is not to give a precise estimate of fNL for each shape but rather we aim to provide a scheme to compute the non-Gaussian contamination due to relativistic projection effects. For the terms considered in this work, we obtain contamination of fNL loc ∼ O(1).

AB - High-precision constraints on primordial non-Gaussianity (PNG) will significantly improve our understanding of the physics of the early universe. Among all the subtleties in using large scale structure observables to constrain PNG, accounting for relativistic corrections to the clustering statistics is particularly important for the upcoming galaxy surveys covering progressively larger fraction of the sky. We focus on relativistic projection effects due to the fact that we observe the galaxies through the light that reaches the telescope on perturbed geodesics. These projection effects can give rise to an effective fNL that can be misinterpreted as the primordial non-Gaussianity signal and hence is a systematic to be carefully computed and accounted for in modelling of the bispectrum. We develop the technique to properly account for relativistic effects in terms of purely observable quantities, namely angles and redshifts. We give some examples by applying this approach to a subset of the contributions to the tree-level bispectrum of the observed galaxy number counts calculated within perturbation theory and estimate the corresponding non-Gaussianity parameter, fNL, for the local, equilateral and orthogonal shapes. For the local shape, we also compute the local non-Gaussianity resulting from terms obtained using the consistency relation for observed number counts. Our goal here is not to give a precise estimate of fNL for each shape but rather we aim to provide a scheme to compute the non-Gaussian contamination due to relativistic projection effects. For the terms considered in this work, we obtain contamination of fNL loc ∼ O(1).

KW - cosmological parameters from LSS

KW - cosmological perturbation theory

KW - gravity

KW - non-gaussianity

UR - http://www.scopus.com/inward/record.url?scp=85017131157&partnerID=8YFLogxK

U2 - 10.1088/1475-7516/2017/03/006

DO - 10.1088/1475-7516/2017/03/006

M3 - Article

AN - SCOPUS:85017131157

VL - 2017

JO - Journal of Cosmology and Astroparticle Physics

JF - Journal of Cosmology and Astroparticle Physics

SN - 1475-7516

IS - 3

M1 - 006

ER -