KiDS-1000: Cross-correlation with Planck cosmic microwave background lensing and intrinsic alignment removal with self-calibration

¹ Shanghai Astronomical Observatory (SHAO), Nandan Road 80, Shanghai 200030, PR China
e-mail: ji.yao@shao.ac.cn; hyshan@shao.ac.cn
² Department of Astronomy, School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240, PR China
e-mail: zhangpj@sjtu.edu.cn
³ Shanghai Key Laboratory for Particle Physics and Cosmology, Shanghai 200240, PR China
⁴ Tsung-Dao Lee Institute, Shanghai 200240, PR China
⁵ South-Western Institute for Astronomy Research, Yunnan University, Kunming 650500, PR China
⁶ Institute for Astronomy, University of Edinburgh, Royal Observatory, Blackford Hill, Edinburgh EH9 3HJ, UK
⁷ Ruhr-Universität Bochum, Astronomisches Institut, German Centre for Cosmological Lensing (GCCL), Universitätsstr. 150, 44801 Bochum, Germany
⁸ Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, UK
⁹ E.A Milne Centre, University of Hull, Cottingham Road, Hull HU6 7RX, UK
¹⁰ Center for Theoretical Physics, Polish Academy of Sciences, al. Lotników 32/46, 02-668 Warsaw, Poland
¹¹ Leiden Observatory, Leiden University, PO Box 9513, 2300 RA Leiden, The Netherlands
¹² Argelander-Institut für Astronomie, Universität Bonn, Auf dem Hügel 71, 53121 Bonn, Germany

Received: 30 January 2023
Accepted: 14 March 2023

Abstract

Context. Galaxy shear and cosmic microwave background (CMB) lensing convergence cross-correlations contain additional information on cosmology with respect to auto-correlations. While remaining immune to certain systemic effects, these cross-correlations are nonetheless affected by the galaxy’s intrinsic alignments (IA). These effects may, in fact, be responsible for the reported low lensing amplitude of the galaxy shear × CMB convergence cross-correlations, compared to the standard PlanckΛCDM (cosmological constant and cold dark matter) cosmology predictions.

Aims. In this work, we investigate how IA affects the Kilo-Degree Survey (KiDS) galaxy lensing shear and Planck CMB lensing convergence cross-correlation and we compare it to previous treatments, both with and without IA taken into consideration.

Methods. We compared the marginalization over IA parameters and the IA self-calibration (SC) method (with additional observables defined only from the source galaxies) to demonstrate that SC can efficiently break the degeneracy between the CMB lensing amplitude, A_lens, and the IA amplitude, A_IA. We further investigated how different systematics affect the resulting A_IA and A_lens and we validated our results with the MICE2 simulation.

Results. We find that by including the SC method to constrain IA, the information loss due to the degeneracy between CMB lensing and IA is strongly reduced. The best-fit values are A_lens = 0.84_−0.22^+0.22 and A_IA = 0.60_−1.03^+1.03, while different angular scale cuts can affect A_lens by ∼10%. We show that an appropriate treatment of the boost factor, cosmic magnification, and photometric redshift modeling is important for obtaining the correct IA and cosmological results.