Sample variance in weak lensing: How many simulations are required?
Constraining cosmology using weak gravitational lensing consists of comparing a measured feature vector of dimension N _{b} with its simulated counterpart. An accurate estimate of the N _{b} × N _{b} feature covariance matrix C is essential to obtain accurate parameter confidence intervals. When C is measured from a set of simulations, an important question is how large this set should be. To answer this question, we construct different ensembles of N _{r} realizations of the shear field, using a common randomization procedure that recycles the outputs from a smaller number N _{s} ≤ N _{r} of independent raytracing Nbody simulations. We study parameter confidence intervals as a function of (N _{s}, N _{r}) in the range 1 ≤ N _{s} ≤ 200 and 1 ≤ N _{r} ≲ 105. Previous work [S. Dodelson and M. D. Schneider, Phys. Rev. D 88, 063537 (2013)] has shown that Gaussian noise in the feature vectors (from which the covariance is estimated) lead, at quadratic order, to an O(1/N _{r}) degradation of the parameter confidence intervals. Using a variety of lensing features measured in our simulations, including shearshear power spectra and peak counts, we show that cubic and quartic covariance fluctuations lead tomore »
 Authors:

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 Columbia Univ., New York, NY (United States); Brookhaven National Lab. (BNL), Upton, NY (United States)
 Brookhaven National Lab. (BNL), Upton, NY (United States)
 Columbia Univ., New York, NY (United States)
 Publication Date:
 Report Number(s):
 BNL1119512016JA
Journal ID: ISSN 24700010; PRVDAQ; KA2301020
 Grant/Contract Number:
 SC00112704; AC0298CH10886; SC0012704; ACI1053575
 Type:
 Accepted Manuscript
 Journal Name:
 Physical Review D
 Additional Journal Information:
 Journal Volume: 93; Journal Issue: 6; Journal ID: ISSN 24700010
 Publisher:
 American Physical Society (APS)
 Research Org:
 Brookhaven National Laboratory (BNL), Upton, NY (United States)
 Sponsoring Org:
 USDOE Office of Science (SC), High Energy Physics (HEP) (SC25)
 Country of Publication:
 United States
 Language:
 English
 Subject:
 79 ASTRONOMY AND ASTROPHYSICS
 OSTI Identifier:
 1245392
 Alternate Identifier(s):
 OSTI ID: 1243154