KiDS-1000 Cosmology: Constraints beyond flat ΛCDM

¹ Institute for Astronomy, University of Edinburgh, Royal Observatory, Blackford Hill, Edinburgh EH9 3HJ, UK
e-mail: ttr@roe.ac.uk
² Centre for Astrophysics & Supercomputing, Swinburne University of Technology, PO Box 218 Hawthorn, VIC 3122, Australia
³ Ruhr-Universität Bochum, Astronomisches Institut, German Centre for Cosmological Lensing (GCCL), Universitätsstr. 150, 44801 Bochum, Germany
⁴ Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, UK
⁵ Max-Planck-Institut für Extraterrestrische Physik, Postfach 1312, Giessenbachstrasse 1, 85741 Garching, Germany
⁶ Center for Theoretical Physics, Polish Academy of Sciences, Al. Lotników 32/46, 02-668 Warsaw, Poland
⁷ Département de Physique Théorique, Université de Genève, 24 Quai Ernest Ansermet, 1211 Genève 4, Switzerland
⁸ Institute of Space Sciences (ICE, CSIC), Campus UAB, Carrer de Can Magrans, s/n, 08193 Barcelona, Spain
⁹ Institut d’Estudis Espacials de Catalunya (IEEC), Carrer Gran Capita 2, 08034 Barcelona, Spain
¹⁰ Argelander-Institut für Astronomie, Universität Bonn, Auf dem Hügel 71, 53121 Bonn, Germany
¹¹ Leiden Observatory, Leiden University, Niels Bohrweg 2, 2333 CA Leiden, The Netherlands
¹² Department of Physics, University of Oxford, Denys Wilkinson Building, Keble Road, Oxford OX1 3RH, UK
¹³ Department of Astrophysical Sciences, Princeton University, 4 Ivy Lane, Princeton, NJ 08544, USA
¹⁴ Centre for Gravitational Astrophysics, College of Science, Australian National University, Acton, ACT 2601, Australia
¹⁵ Research School of Astronomy and Astrophysics, Australian National University, Canberra, ACT 2600, Australia
¹⁶ Institut de Ciències del Cosmos, Universitat de Barcelona, Martí Franquès 1, 08028 Barcelona, Spain
¹⁷ Korea Astronomy and Space Science Institute, 776 Daedeokdae-ro, Yuseong-gu, Daejeon 34055, Republic of Korea
¹⁸ Shanghai Astronomical Observatory (SHAO), Nandan Road 80, Shanghai 200030, PR China
¹⁹ University of Chinese Academy of Sciences, Beijing 100049, PR China

Received: 30 October 2020
Accepted: 17 February 2021

Abstract

We present constraints on extensions to the standard cosmological model of a spatially flat Universe governed by general relativity, a cosmological constant (Λ), and cold dark matter (CDM) by varying the spatial curvature Ω_K, the sum of the neutrino masses ∑m_ν, the dark energy equation of state parameter w, and the Hu-Sawicki f(R) gravity f_R0 parameter. With the combined 3 × 2 pt measurements of cosmic shear from the Kilo-Degree Survey (KiDS-1000), galaxy clustering from the Baryon Oscillation Spectroscopic Survey (BOSS), and galaxy-galaxy lensing from the overlap between KiDS-1000, BOSS, and the spectroscopic 2-degree Field Lensing Survey, we find results that are fully consistent with a flat ΛCDM model with Ω_K = 0.011_−0.057^+0.054, ∑m_ν < 1.76 eV (95% CL), and w = −0.99_−0.13^+0.11. The f_R0 parameter is unconstrained in our fully non-linear f(R) cosmic shear analysis. Considering three different model selection criteria, we find no clear preference for either the fiducial flat ΛCDM model or any of the considered extensions. In addition to extensions to the flat ΛCDM parameter space, we also explore restrictions to common subsets of the flat ΛCDM parameter space by fixing the amplitude of the primordial power spectrum to the Planck best-fit value, as well as adding external data from supernovae and lensing of the cosmic microwave background (CMB). Neither the beyond-ΛCDM models nor the imposed restrictions explored in this analysis are able to resolve the ∼3σ tension in S₈ between the 3 × 2 pt constraints and the Planck temperature and polarisation data, with the exception of wCDM, where the S₈ tension is resolved. The tension in the wCDM case persists, however, when considering the joint S₈ − w parameter space. The joint flat ΛCDM CMB lensing and 3 × 2 pt analysis is found to yield tight constraints on Ω_m = 0.307_−0.013^+0.008, σ₈ = 0.769_−0.010^+0.022, and S₈ = 0.779_−0.013^+0.013.