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Article Dans Une Revue Astronomy and Astrophysics - A&A Année : 2008

Comparing cosmic shear measures. Optimizing the information content of cosmic shear data vectors

T. Eifler
  • Fonction : Auteur
M. Kilbinger
P. Schneider

Résumé

Aims: We introduce an optimized data vector of cosmic shear measures (N). This data vector has high information content, is not sensitive to B-mode contamination, and only shows small correlation between data points of different angular scales.
Methods: We show that a data vector of the two-point correlation function (2PCF), hereafter denoted as ξ, in general contains more information on cosmological parameters compared to a data vector of the aperture mass dispersion, hereafter referred to as < M_ap2 >. The reason for this is the fact that < M_ap2 > lacks the information of the convergence power spectrum (P_κ) on large angular scales, which is contained in ξ. Nevertheless, < M_ap2 > has valuable properties (small correlation between data points of different angular scales, not sensitive to B-mode contamination) that one wants to preserve in an optimized data vector. Therefore we combine ξ and < M_ap2 > to a new data vector N=( < M_ap^2> (θ_1), ..., < M_ap^2> (θ_n), ξ_+(θ_0) ), which retains the advantages of < M_ap2 > and is also sensitive to the large-scale information of P_κ. We compare the information content of the three data vectors by performing a detailed likelihood analysis and use ray-tracing simulations to derive the covariance matrices. In the last part of the paper we contaminate all data vectors with B-modes on small angular scales and examine their robustness against this contamination.
Results: The combined data vector N strongly improves constraints on cosmological parameters compared to < M_ap2 >. Although, the information content of ξ is higher in the case of a pure E-mode signal, in the more realistic case where B-modes are present the 2PCF data vector is strongly contaminated and yields biased cosmological parameter estimates. The new data vector N shows to be robust against this contamination. Furthermore the individual data points of N show a much smaller correlation compared to ξ, leading to an almost diagonal covariance matrix.
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Dates et versions

hal-03646472 , version 1 (30-04-2022)

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T. Eifler, M. Kilbinger, P. Schneider. Comparing cosmic shear measures. Optimizing the information content of cosmic shear data vectors. Astronomy and Astrophysics - A&A, 2008, 482, pp.9-19. ⟨10.1051/0004-6361:20078573⟩. ⟨hal-03646472⟩
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