Abstract
ABSTRACT We investigate the prospects for using the weak lensing bispectrum alongside the power spectrum to control systematic uncertainties in a Euclid-like survey. Three systematic effects are considered: the intrinsic alignment of galaxies, uncertainties in the means of tomographic redshift distributions, and multiplicative bias in the measurement of the shear signal. We find that the bispectrum is very effective in mitigating these systematic errors. Varying all three systematics simultaneously, a joint power spectrum and bispectrum analysis reduces the area of credible regions for the cosmological parameters Ωm and σ8 by a factor of 90 and for the two parameters of a time-varying dark energy equation of state by a factor of almost 20, compared with the baseline approach of using the power spectrum alone and of imposing priors consistent with the accuracy requirements specified for Euclid. We also demonstrate that including the bispectrum self-calibrates all three systematic effects to the stringent levels required by the forthcoming generation of weak lensing surveys, thereby reducing the need for external calibration data.
Highlights
One of the primary aims of modern cosmology is to constrain cosmological parameters within the concordance cosmological model
17.0 wide priors of 10 are imposed on all nuisance parameters; when default priors are imposed on each type of nuisance parameter in turn, but wide priors are imposed on the remaining parameters; and when no systematics are present – this can be considered as a baseline that exemplifies the maximum attainable information content
In the context of a Euclid-like tomographic weak lensing survey we have considered three major sources of systematic uncertainty: contamination by intrinsic alignments which adds additional terms to the cosmic shear power spectrum and bispectrum; uncertainty in the mean redshifts of the tomographic bins due to the use of photometric redshift measurements; and multiplicative bias that affects the amplitude of the shear signal
Summary
One of the primary aims of modern cosmology is to constrain cosmological parameters within the concordance cosmological model. An increasingly reliable tool for this purpose is weak gravitational lensing. Recent galaxy surveys including the Kilo-Degree Survey (KiDS), the Dark Energy Survey (DES), and the Hyper SuprimeCam Subaru Strategic Survey (HSC) have already produced strong constraints on parameters of structure growth (Troxel et al 2018; Hikage et al 2019; Asgari et al 2021). Rubin Observatory Legacy Survey of Space and Time (LSST) will represent a step change in the quantity and precision of weak lensing data and deliver even tighter parameter constraints. The increased volume and accuracy of the data will make it possible to use methods and statistics which are not feasible with current surveys
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
