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Improving lognormal models for cosmological fields

Xavier, HS; Abdalla, FB; Joachimi, B; (2016) Improving lognormal models for cosmological fields. Monthly Notices of the Royal Astronomical Society (MNRAS) , 459 (4) pp. 3693-3710. 10.1093/mnras/stw874. Green open access

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Abstract

It is common practice in cosmology to model large-scale structure observables as lognormal random fields, and this approach has been successfully applied in the past to the matter density and weak lensing convergence fields separately. We argue that this approach has fundamental limitations which prevent its use for jointly modelling these two fields since the lognormal distribution's shape can prevent certain correlations to be attainable. Given the need of ongoing and future large-scale structure surveys for fast joint simulations of clustering and weak lensing, we propose two ways of overcoming these limitations. The first approach slightly distorts the power spectra of the fields using one of two algorithms that minimises either the absolute or the fractional distortions. The second one is by obtaining more accurate convergence marginal distributions, for which we provide a fitting function, by integrating the lognormal density along the line of sight. The latter approach also provides a way to determine directly from theory the skewness of the convergence distribution and, therefore, the parameters for a lognormal fit. We present the public code Full-sky Lognormal Astro-fields Simulation Kit (FLASK) which can make tomographic realisations on the sphere of an arbitrary number of correlated lognormal or Gaussian random fields by applying either of the two proposed solutions, and show that it can create joint simulations of clustering and lensing with sub-per-cent accuracy over relevant angular scales and redshift ranges.

Type: Article
Title: Improving lognormal models for cosmological fields
Open access status: An open access version is available from UCL Discovery
DOI: 10.1093/mnras/stw874
Publisher version: http://dx.doi.org/10.1093/mnras/stw874
Language: English
Additional information: This is a pre-copyedited, author-produced PDF of an article accepted for publication in Monthly Notices of the Royal Astronomical Society (MNRAS following peer review. The version of record Xavier, HS; Abdalla, FB; Joachimi, B; (2016) Improving lognormal models for cosmological fields. Monthly Notices of the Royal Astronomical Society (MNRAS) , 459 (4) pp. 3693-3710. 10.1093/mnras/stw874 is available online at: http://dx.doi.org/10.1093/mnras/stw874. 19 pages, 21 figures. Submitted to MNRAS. FLASK code can be found at: http://www.astro.iag.usp.br/~flask
Keywords: astro-ph.CO, astro-ph.CO
UCL classification: UCL
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Physics and Astronomy
URI: https://discovery-pp.ucl.ac.uk/id/eprint/1498779
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