A Point-Transformed Gaussian Model for Field-Level Mass Distributions in Tomographic Density Slabs

Abstract

The work presented in this talk is part of a program of performing field-level cosmological analyses using galaxy and weak lensing observables in density slabs of $O[100\ \mathrm{Mpc}]$. The inference pipeline requires a model for the mass overdensity field which is accurate to scales of a few Mpc across cosmologies, and also fast in the generation of sample fields. I will describe a scheme in which the nonlinear mass overdensity field is obtained by applying some point transformation to a Gaussian random field. I will present our transformation function that, with a small number of parameters, characterizes the mass distribution in a slab for different redshifts, slab widths, and cosmologies. I will show that the model accurately reproduces the statistical properties of mass overdensity fields from Gower Street simulations, demonstrating its viability for field-level inference. Finally, I will discuss a validation test which uses the point-transformed Gaussian model to infer the cosmology from the output of an $N$-body simulation.