KiDS-1000 Cosmology: Constraints from density split statistics

TL;DR

This paper uses density split statistics on KiDS-1000 data to improve cosmological constraints by capturing non-Gaussian features of the matter density field, showing results consistent with traditional methods.

Contribution

It introduces a novel application of density split statistics to KiDS-1000 data, providing competitive cosmological constraints and probing galaxy-dark matter connections.

Findings

Measured $S_8$ consistent with cosmic shear results

Constrained matter density $\, ext{Omega}_m$ to 0.28

Estimated galaxy bias as 1.32

Abstract

Context. Weak lensing and clustering statistics beyond two-point functions can capture non-Gaussian information about the matter density field, thereby improving the constraints on cosmological parameters relative to the mainstream methods based on correlation functions and power spectra. Aims. This paper presents a cosmological analysis of the fourth data release of the Kilo Degree Survey based on the density split statistics, which measures the mean shear profiles around regions classified according to foreground densities. The latter is constructed from a bright galaxy sample, which we further split into red and blue samples, allowing us to probe their respective connection to the underlying dark matter density. Methods. We use the state-of-the-art model of the density splitting statistics and validate its robustness against mock data infused with known systematic effects such as intrinsic galaxy alignment and baryonic feedback. Results. After marginalising over the photometric redshift uncertainty and the residual shear calibration bias, we measure for the full KiDS-bright sample a structure growth parameter of $S_8 = \sigma_8 \sqrt{\Omega_\mathrm{m}/0.3} = 0.74^{+0.03}_{-0.02}$ that is competitive to and consistent with two-point cosmic shear results, a matter density of $\Omega_\mathrm{m} = 0.28 \pm 0.02$, and a constant galaxy bias of $b = 1.32^{+0.12}_{-0.10}$.