TY - JOUR

T1 - Dark Energy Survey year 3 results

T2 - covariance modelling and its impact on parameter estimation and quality of fit

AU - Friedrich, O.

AU - Andrade-Oliveira, F.

AU - Camacho, H.

AU - Alves, O.

AU - Rosenfeld, R.

AU - Sanchez, J.

AU - Fang, X.

AU - Eifler, T. F.

AU - Krause, E.

AU - Chang, C.

AU - Omori, Y.

AU - Amon, A.

AU - Baxter, E.

AU - Elvin-Poole, J.

AU - Huterer, D.

AU - Palmese, A.

AU - Paz-Chinchon, F.

AU - Plazas, A. A.

AU - Sanchez, E.

AU - Scarpine, V.

AU - Serrano, S.

AU - Soares-Santos, M.

AU - Smith, M.

AU - Suchyta, E.

AU - Tarle, G.

AU - Thomas, D.

AU - Too, C.

AU - Varga, T. N.

AU - Weller, J.

AU - Wilkinson, R. D.

N1 - Funding Information:
We acknowledge support from the Brazilian Instituto Nacional de Ciencia e Tecnologia (INCT) e-Universe (CNPq grant 465376/2014-2).
Publisher Copyright:
© 2021 The Author(s) 2021. Published by Oxford University Press on behalf of Royal Astronomical Society.

PY - 2021/12/1

Y1 - 2021/12/1

N2 - We describe and test the fiducial covariance matrix model for the combined two-point function analysis of the Dark Energy Survey Year 3 (DES-Y3) data set. Using a variety of new ansatzes for covariance modelling and testing, we validate the assumptions and approximations of this model. These include the assumption of Gaussian likelihood, the trispectrum contribution to the covariance, the impact of evaluating the model at a wrong set of parameters, the impact of masking and survey geometry, deviations from Poissonian shot noise, galaxy weighting schemes, and other sub-dominant effects. We find that our covariance model is robust and that its approximations have little impact on goodness of fit and parameter estimation. The largest impact on best-fitting figure-of-merit arises from the so-called fsky approximation for dealing with finite survey area, which on average increases the χ2 between maximum posterior model and measurement by $3.7{{\ \rm per\ cent} (Δχ2 ≈ 18.9). Standard methods to go beyond this approximation fail for DES-Y3, but we derive an approximate scheme to deal with these features. For parameter estimation, our ignorance of the exact parameters at which to evaluate our covariance model causes the dominant effect. We find that it increases the scatter of maximum posterior values for ωm and σ8 by about $3{{\ \rm per\ cent} and for the dark energy equation-of-state parameter by about $5{{\ \rm per\ cent}.

AB - We describe and test the fiducial covariance matrix model for the combined two-point function analysis of the Dark Energy Survey Year 3 (DES-Y3) data set. Using a variety of new ansatzes for covariance modelling and testing, we validate the assumptions and approximations of this model. These include the assumption of Gaussian likelihood, the trispectrum contribution to the covariance, the impact of evaluating the model at a wrong set of parameters, the impact of masking and survey geometry, deviations from Poissonian shot noise, galaxy weighting schemes, and other sub-dominant effects. We find that our covariance model is robust and that its approximations have little impact on goodness of fit and parameter estimation. The largest impact on best-fitting figure-of-merit arises from the so-called fsky approximation for dealing with finite survey area, which on average increases the χ2 between maximum posterior model and measurement by $3.7{{\ \rm per\ cent} (Δχ2 ≈ 18.9). Standard methods to go beyond this approximation fail for DES-Y3, but we derive an approximate scheme to deal with these features. For parameter estimation, our ignorance of the exact parameters at which to evaluate our covariance model causes the dominant effect. We find that it increases the scatter of maximum posterior values for ωm and σ8 by about $3{{\ \rm per\ cent} and for the dark energy equation-of-state parameter by about $5{{\ \rm per\ cent}.

KW - cosmology: observations

KW - large-scale structure of Universe

UR - http://www.scopus.com/inward/record.url?scp=85119534052&partnerID=8YFLogxK

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U2 - 10.1093/mnras/stab2384

DO - 10.1093/mnras/stab2384

M3 - Article

AN - SCOPUS:85119534052

VL - 508

SP - 3125

EP - 3165

JO - Monthly Notices of the Royal Astronomical Society

JF - Monthly Notices of the Royal Astronomical Society

SN - 0035-8711

IS - 3

ER -