Density split statistics: Cosmological constraints from counts and lensing in cells in DES Y1 and SDSS data

Abstract

We derive cosmological constraints from the probability distribution function (PDF) of evolved large-scale matter density fluctuations. We do this by splitting lines of sight by density based on their count of tracer galaxies, and by measuring both gravitational shear around and counts-in-cells in overdense and underdense lines of sight, in Dark Energy Survey (DES) First Year and Sloan Digital Sky Survey (SDSS) data. Our analysis uses a perturbation theory model [O. Friedrich et al., Phys. Rev. D 98, 023508 (2018)] and is validated using N-body simulation realizations and log-normal mocks. It allows us to constrain cosmology, bias and stochasticity of galaxies with respect to matter density and, in addition, the skewness of the matter density field. From a Bayesian model comparison, we find that the data weakly prefer a connection of galaxies and matter that is stochastic beyond Poisson fluctuations on ≤ 20 arcmin angular smoothing scale. The two stochasticity models we fit yield DES constraints on the matter density Ω m ¼ 0.26 −0.07 for the two stochasticity models), but consistent with each other and with the 3 x 2pt results if stochasticity is at the low end of the posterior range. As an additional test of gravity, counts and lensing in cells allow to compare the skewness S 3 of the matter density PDF to its ΛCDM prediction. We find no evidence of excess skewness in any model or data set, with better than 25 per cent relative precision in the skewness estimate from DES alone.

New perspectives on the BOSS small-scale lensing discrepancy for the Planck ΛCDM cosmology

“…Wibking et al 2019;DeRose et al 2019;Zhai et al 2019;Nishimichi et al 2018). In addition, further advances will come from combining galaxy clustering and galaxy-galaxy lensing with additional, alternative probes of large-scale structure, such as redshift space distortions (e.g., Yang et al 2008;Reid et al 2014), satellite kinematics (e.g., More et al 2011;Lange et al 2019), higher-order correlation functions (Gil-Marín et al 2017;Gualdi et al 2019), cosmic shear (e.g, Fu et al 2014;Hildebrandt et al 2017), and counts-in-cells (e.g., Reid & Spergel 2009;Gruen et al 2018). Such additional data will prove especially important for breaking degeneracies and constraining galaxy assembly bias (see e.g., Wang et al 2019).…”

How to optimally constrain galaxy assembly bias: supplement projected correlation functions with count-in-cells statistics

“…The complementarity between ∆Σ(r p ) and P(N CIC ) is not unexpected. The lensing signal traces the matter density contrast around galaxies while the counts-in-cylinders statistics probe the galaxy distribution profiles in approximately the same regions, and are therefore expected to complement each other in constraining cosmology as well as the connection between galaxies and the matter field (Gruen et al 2018;Friedrich et al 2018).…”

“…Galaxy counts, particularly counts of galaxies within cylindrical volumes in redshift space, have been studied for decades (e.g., Fry & Peebles 1978;Balian & Schaeffer 1988;Alimi et al 1990;Baugh et al 1995;Colombi et al 1995;Szapudi et al 1996;Kim & Strauss 1998;Hogg et al 2004;Kauffmann et al 2004;Blanton et al 2006;Barton et al 2007;Reid & Spergel 2009;Berrier et al 2011;Oguri & Lin 2015;Gruen et al 2018). The average number of companions that a galaxy will have within a particular cylinder can be computed from the two-point correlation function; however, the distribution of counts-in-cylinders depends, at least in principle, upon all of the higher n-point functions (Peebles 1980) and can complement the two-point function as a study of the galaxy halo relationship.…”

A nulling strategy for modelling lensing convergence in cones with large deviation theory

“…Another promising avenue will be to combine weaklensing and galaxy clustering in the spirit of the so-called density-split statistics (Friedrich et al 2018;Gruen et al 2018) that is able to constrain cosmological parameters even if some degrees of freedom are left such as the galaxy bias and galaxy-matter correlation coefficients. Indeed, one can deduce the tangential shear profile around a line-of-sight with given tracer density from the convergence profile.…”

“…Cosmic shear experiments like DES and KiDS are sensitive to the matter distribution itself and can be used to extract the weak-lensing signal around shear peaks (Kacprzak et al 2016), galaxy troughs and ridges (Gruen et al 2016;Brouwer et al 2018) or more general density split statistics (Friedrich et al 2018;Gruen et al 2018). In particular, Friedrich et al (2018) used the cumulant generating function to construct the one-point PDF of galaxy densities in cones and the weak-lensing convergence profile around line-of-sight with given galaxy density.…”