Testing the lognormality of the galaxy and weak lensing convergence distributions from Dark Energy Survey maps
نویسندگان
چکیده
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 (κWL) is lognormal is less well established. We derive PDFs of the galaxy and projected matter density distributions via the Counts in Cells (CiC) method. We use maps of galaxies and weak lensing convergence produced from the Dark Energy Survey (DES) Science Verification data over 139 deg. 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 modeled by a lognormal PDF convolved with Poisson noise at angular scales from 1040(corresponding to physical scales of 3–10 Mpc). We note that as κWL 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 κWL distribution is well modeled by a lognormal PDF convolved with Gaussian shape noise at scales between 10and 20, with a best-fit χ/DOF of 1.11 compared to 1.84 for a Gaussian model, corresponding to p-values 0.35 and 0.07 respectively, at a scale of 10. Above 20a 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 N-body simulation.
منابع مشابه
How Sensitive Are Weak Lensing Statistics to Dark Energy Content?
Future weak lensing surveys will directly probe the clustering of dark matter, in addition to providing a test for various cosmological models. Recent studies have provided us with the tools which can be used to construct the complete probability distribution function for convergence fields. It is also possible to construct the bias associated with the hot-spots in convergence maps. These techn...
متن کاملMeasuring the Galaxy-Galaxy-Mass Three-point Correlation Function with Weak Gravitational Lensing
We discuss the galaxy-galaxy-mass three-point correlation function and show how to measure it with weak gravitational lensing. The method entails choosing a large of pairs of foreground lens galaxies and constructing a mean shear map with respect to their axis, by averaging the ellipticities of background source galaxies. An average mass map can be reconstructed from this shear map and this wil...
متن کاملThe Dark Energy Survey Science Program
The Dark Energy Survey (DES) will enable measurements of the dark energy and dark matter densities and the dark energy equation of state through four independent methods: galaxy clusters, weak gravitational lensing, galaxy angular clustering (baryon acoustic oscillations), and supernovae. These methods, highlighted by the Dark Energy Task Force Report (DETF) as the most promising, are doubly co...
متن کاملBeating Lensing Cosmic Variance with Galaxy Tomography
I discuss the use of cross correlations between galaxies with distance information and projected weak lensing dark matter maps to obtain a fully three dimensional dark matter map and power spectrum. On large scales l . 200 one expects the galaxies to be biased, but not stochastic. I show that this allows a simultaneous solution of the full 3-D evolving galaxy bias and the dark matter power spec...
متن کاملWeak Lensing from Space Ii: Dark Matter Mapping
We study the accuracy with which weak lensing measurements can be made from space, and the subsequent resolution of both 3-dimensional and projected 2-dimensional dark matter maps. As a baseline, we use the instrumental specifications of the Supernova/Acceleration Probe (SNAP) satellite. We compute the sensitivity to shear as a function of depth for space-based observations. Our predictions are...
متن کامل