Imperial College London
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ProfessorAlanHeavens

Faculty of Natural Sciences, Department of Physics

Chair in Astrostatistics
 
 
 
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Contact

 

+44 (0)20 7594 2930a.heavens Website

 
 
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Location

 

1018EBlackett LaboratorySouth Kensington Campus

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Summary

 

Publications

Citation

BibTex format

@article{Heavens:2017:mnras/stx2491,
author = {Heavens, AF and Sellentin, E},
doi = {mnras/stx2491},
journal = {Monthly Notices of the Royal Astronomical Society},
pages = {2355--2363},
title = {On the insufficiency of arbitrarily precise covariance matrices: non-Gaussian weak lensing likelihoods},
url = {http://dx.doi.org/10.1093/mnras/stx2491},
volume = {473},
year = {2017}
}
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RIS format (EndNote, RefMan)

TY  - JOUR
AB  - We investigate whether a Gaussian likelihood, as routinely assumed in the analysis of cosmologicaldata, is supported by simulated survey data. We define test statistics, based on anovel method that first destroys Gaussian correlations in a data set, and then measures the nonGaussiancorrelations that remain. This procedure flags pairs of data points that depend on eachother in a non-Gaussian fashion, and thereby identifies where the assumption of a Gaussianlikelihood breaks down. Using this diagnosis, we find that non-Gaussian correlations in theCFHTLenS cosmic shear correlation functions are significant. With a simple exclusion of themost contaminated data points, the posterior for s8 is shifted without broadening, but we findno significant reduction in the tension with s8 derived from Planck cosmic microwave backgrounddata. However, we also show that the one-point distributions of the correlation statisticsare noticeably skewed, such that sound weak-lensing data sets are intrinsically likely to leadto a systematically low lensing amplitude being inferred. The detected non-Gaussianities getlarger with increasing angular scale such that for future wide-angle surveys such as Euclidor LSST, with their very small statistical errors, the large-scale modes are expected to beincreasingly affected. The shifts in posteriors may then not be negligible and we recommendthat these diagnostic tests be run as part of future analyses.
AU  - Heavens,AF
AU  - Sellentin,E
DO  - mnras/stx2491
EP  - 2363
PY  - 2017///
SN  - 0035-8711
SP  - 2355
TI  - On the insufficiency of arbitrarily precise covariance matrices: non-Gaussian weak lensing likelihoods
T2  - Monthly Notices of the Royal Astronomical Society
UR  - http://dx.doi.org/10.1093/mnras/stx2491
UR  - http://hdl.handle.net/10044/1/51216
VL  - 473
ER  -
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