Density split statistics: joint model of counts and lensing in cells

TL;DR

This paper introduces density split statistics, a novel framework combining lensing and counts-in-cells to probe cosmology and galaxy-matter connections using large-scale measurements.

Contribution

It extends previous work by modeling joint lensing and counts-in-cells statistics as functions of galaxy density, enabling new cosmological insights.

Findings

Model accurately reproduces simulation results

Effective for cosmological analysis with DES Year 1 data

Provides a new method to connect galaxy density and matter distribution

Abstract

We present density split statistics, a framework that studies lensing and counts-in-cells as a function of foreground galaxy density, thereby providing a large-scale measurement of both 2-point and 3-point statistics. Our method extends our earlier work on trough lensing and is summarized as follows: given a foreground (low redshift) population of galaxies, we divide the sky into subareas of equal size but distinct galaxy density. We then measure lensing around uniformly spaced points separately in each of these subareas, as well as counts-in-cells statistics (CiC). The lensing signals trace the matter density contrast around regions of fixed galaxy density. Through the CiC measurements this can be related to the density profile around regions of fixed matter density. Together, these measurements constitute a powerful probe of cosmology, the skewness of the density field and the connection of galaxies and matter. In this paper we show how to model both the density split lensing signal and CiC from basic ingredients: a non-linear power spectrum, clustering hierarchy coefficients from perturbation theory and a parametric model for galaxy bias and shot-noise. Using N-body simulations, we demonstrate that this model is sufficiently accurate for a cosmological analysis on year 1 data from the Dark Energy Survey.