KiDS+VIKING-450 and DES-Y1 combined: Mitigating baryon feedback uncertainty with COSEBIs

¹ Institute for Astronomy, University of Edinburgh, Royal Observatory, Blackford Hill, Edinburgh EH9 3HJ, UK
e-mail: ma@roe.ac.uk
² German Centre for Cosmological Lensing, Astronomisches Institut, Ruhr-Universität Bochum, Universitätsstr. 150, 44801 Bochum, Germany
³ Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, UK
⁴ Argelander-Institut für Astronomie, Auf dem Hügel 71, 53121 Bonn, Germany
⁵ Center for Cosmology and AstroParticle Physics, The Ohio State University, 191 West Woodruff Avenue, Columbus, OH 43210, USA
⁶ Department of Physics, University of Oxford, Denys Wilkinson Building, Keble Road, Oxford OX1 3RH, UK
⁷ Leiden Observatory, Leiden University, Niels Bohrweg 2, 2333 CA Leiden, The Netherlands

Received: 15 August 2019
Accepted: 21 January 2020

Abstract

We present cosmological constraints from a joint cosmic shear analysis of the Kilo-Degree Survey (KV450) and the Dark Energy Survey (DES-Y1), which were conducted using Complete Orthogonal Sets of E/B-Integrals (COSEBIs). With COSEBIs, we isolated any B-modes that have a non-cosmic shear origin and demonstrate the robustness of our cosmological E-mode analysis as no significant B-modes were detected. We highlight how COSEBIs are fairly insensitive to the amplitude of the non-linear matter power spectrum at high k-scales, mitigating the uncertain impact of baryon feedback in our analysis. COSEBIs, therefore, allowed us to utilise additional small-scale information, improving the DES-Y1 joint constraints on S₈ = σ₈(Ω_m/0.3)^0.5 and Ω_m by 20%. By adopting a flat ΛCDM model we find S₈ = 0.755_−0.021^+0.019, which is in 3.2σ tension with the Planck Legacy analysis of the cosmic microwave background.