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Abstract
We present a mitigation strategy to reduce the impact of nonlinear galaxy bias on the joint ‘3×2pt’ cosmological analysis of weak lensing and galaxy surveys. The Ψstatistics that we adopt are based on Complete Orthogonal Sets of E/B Integrals (COSEBIs). As such they are designed to minimise the contributions to the observable from the smallest physical scales where models are highly uncertain. We demonstrate that Ψstatistics carry the same constraining power as the standard twopoint galaxy clustering and galaxygalaxy lensing statistics, but are significantly less sensitive to scaledependent galaxy bias. Using two galaxy bias models, motivated by halomodel fits to data and simulations, we quantify the error in a standard 3×2pt analysis where constant galaxy bias is assumed. Even when adopting conservative angular scale cuts, that degrade the overall cosmological parameter constraints, we find of order 1σ biases for Stage III surveys on the cosmological parameter S8 = σ8(Ωm/0.3)α. This arises
from a leakage of the smallest physical scales to all angular scales in the standard twopoint correlation functions. In contrast, when analysing Ψstatistics under the same approximation of constant galaxy bias, we show that the bias on the recovered value for S8 can be decreased by a factor of ∼ 2, with less conservative scale cuts. Given the challenges in determining accurate galaxy bias models in the highly nonlinear regime, we argue that 3 × 2pt analyses
should move towards new statistics that are less sensitive to the smallest physical scales.
from a leakage of the smallest physical scales to all angular scales in the standard twopoint correlation functions. In contrast, when analysing Ψstatistics under the same approximation of constant galaxy bias, we show that the bias on the recovered value for S8 can be decreased by a factor of ∼ 2, with less conservative scale cuts. Given the challenges in determining accurate galaxy bias models in the highly nonlinear regime, we argue that 3 × 2pt analyses
should move towards new statistics that are less sensitive to the smallest physical scales.
Original language  English 

Pages (fromto)  30033016 
Number of pages  14 
Journal  Monthly Notices of the Royal Astronomical Society 
Volume  501 
Issue number  2 
Early online date  10 Dec 2020 
DOIs  
Publication status  Published  1 Feb 2021 
Keywords
 astroph.CO
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Projects
 1 Active

GLOBE: Global Lensing Observations to go Beyond Einstein (027451/1)
1/11/15 → 31/10/21
Project: Research