KiDS-1000 cosmology: Combined second- and third-order shear statistics

¹ University of Bonn, Argelander-Institut für Astronomie, Auf dem Hügel 71, 53121 Bonn, Germany
e-mail: pburger@astro.uni-bonn.de
² Universität Innsbruck, Institut für Astro- und Teilchenphysik, Technikerstr. 25/8, 6020 Innsbruck, Austria
³ Department of Astronomy and Astrophysics, University of California, Santa Cruz, 1156 High Street, Santa Cruz, CA 95064, USA
⁴ E.A Milne Centre, University of Hull, Cottingham Road, Hull HU6 7RX, UK
⁵ INAF – Osservatorio Astronomico di Trieste, via Tiepolo 11, 34131 Trieste, Italy
⁶ INFN – Sezione di Trieste, 34100 Trieste, Italy
⁷ IFPU – Institute for Fundamental Physics of the Universe, via Beirut 2, 34151 Trieste, Italy
⁸ Universitäts-Sternwarte, Fakultät für Physik, Ludwig-Maximilians-Universität München, Scheinerstr.1, 81679 München, Germany
⁹ Max-Planck-Institut für Astrophysik, Karl-Schwarzschild-Straße 1, 85741 Garching, Germany
¹⁰ School of Mathematics, Statistics and Physics, Newcastle University, Newcastle upon Tyne NE1 7RU, UK
¹¹ Ruhr University Bochum, Faculty of Physics and Astronomy, Astronomical Institute (AIRUB), German Centre for Cosmological Lensing, 44780 Bochum, Germany
¹² Leiden Observatory, Leiden University, PO Box 9513 2300 RA Leiden, The Netherlands
¹³ Aix-Marseille Université, CNRS, CNES, LAM, Marseille, France

Received: 15 September 2023
Accepted: 6 December 2023

Abstract

Aims. In this work, we perform the first cosmological parameter analysis of the fourth release of Kilo Degree Survey (KiDS-1000) data with second- and third-order shear statistics. This paper builds on a series of studies aimed at describing the roadmap to third-order shear statistics.

Methods. We derived and tested a combined model of the second-order shear statistic, namely, the COSEBIs and the third-order aperture mass statistics 〈ℳ_ap³〉 in a tomographic set-up. We validated our pipeline with N-body mock simulations of the KiDS-1000 data release. To model the second- and third-order statistics, we used the latest version of HMCODE2020 for the power spectrum and BIHALOFIT for the bispectrum. Furthermore, we used an analytic description to model intrinsic alignments and hydro-dynamical simulations to model the effect of baryonic feedback processes. Lastly, we decreased the dimension of the data vector significantly by considering only equal smoothing radii for the 〈ℳ_ap³〉 part of the data vector. This makes it possible to carry out a data analysis of the KiDS-1000 data release using a combined analysis of COSEBIs and third-order shear statistics.

Results. We first validated the accuracy of our modelling by analysing a noise-free mock data vector, assuming the KiDS-1000 error budget, finding a shift in the maximum of the posterior distribution of the matter density parameter, ΔΩ_m < 0.02 σ_Ωm, and of the structure growth parameter, ΔS₈ < 0.05 σ_S8. Lastly, we performed the first KiDS-1000 cosmological analysis using a combined analysis of second- and third-order shear statistics, where we constrained Ω_m = 0.248_−0.055^+0.062 and S₈ = σ₈√(Ω_m/0.3 )= 0.772 ± 0.022. The geometric average on the errors of Ω_m and S₈ of the combined statistics decreases, compared to the second-order statistic, by a factor of 2.2.