Abstract
It is common practice in cosmology to use lognormal random fields to model large-scale structure observables such as matter density and weak lensing convergence. I will present the public code Full-sky Lognormal Astro-fields Simulation Kit (FLASK) which can make tomographic realizations on spherical shells around the observer of an arbitrary number of correlated lognormal or Gaussian random fields, including the Cosmic Microwave Background (CMB) and multiple tracers of matter. I will show that lognormal fields have fundamental limitations which prevent its use for jointly modelling density and convergence and will propose two ways of overcoming these limitations. The first approach slightly distorts the power spectra of the fields while the second one generates a different weak lensing convergence marginal distribution 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.
