Testing the lognormality of the galaxy and weak lensing convergence distributions from Dark Energy Survey maps
Abstract
It is well known that the probability distribution function (PDF) of galaxy density contrast is approximately lognormal; whether the PDF of mass fluctuations derived from weak lensing convergence (κ_{WL}) is lognormal is less well established. We derive PDFs of the galaxy and projected matter density distributions via the countsincells (CiC) method. We use maps of galaxies and weak lensing convergence produced from the Dark Energy Survey Science Verification data over 139 deg^{2}. We test whether the underlying density contrast is well described by a lognormal distribution for the galaxies, the convergence and their joint PDF. We confirm that the galaxy density contrast distribution is well modelled by a lognormal PDF convolved with Poisson noise at angular scales from 10 to 40 arcmin (corresponding to physical scales of 310 Mpc). We note that as κ_{WL} is a weighted sum of the mass fluctuations along the line of sight, its PDF is expected to be only approximately lognormal. We find that the κ_{WL} distribution is well modelled by a lognormal PDF convolved with Gaussian shape noise at scales between 10 and 20 arcmin, with a bestfitting χ^{2}/dof of 1.11 compared to 1.84 for a Gaussian model, corresponding to pvalues 0.35 and 0.07, respectively, at a scale of 10 arcmin. Above 20 arcmin a simple Gaussian model is sufficient. The joint PDF is also reasonably fitted by a bivariate lognormal. As a consistency check, we compare the variances derived from the lognormal modelling with those directly measured via CiC. Our methods are validated against maps from the MICE Grand Challenge Nbody simulation.
 Publication:

Monthly Notices of the Royal Astronomical Society
 Pub Date:
 April 2017
 DOI:
 10.1093/mnras/stw2106
 arXiv:
 arXiv:1605.02036
 Bibcode:
 2017MNRAS.466.1444C
 Keywords:

 gravitational lensing: weak;
 cosmology: observations;
 largescale structure of Universe;
 Astrophysics  Cosmology and Nongalactic Astrophysics
 EPrint:
 17 pages, 14 figures, submitted to MNRAS