ShapePipe: A new shape measurement pipeline and weak-lensing application to UNIONS/CFIS data

¹ AIM, CEA, CNRS, Université Paris-Saclay, Université de Paris, 91191 Gif-sur-Yvette, France
e-mail: axel.guinot.astro@gmail.com
² Université de Paris, CNRS, Astroparticule et Cosmologie, 75013 Paris, France
³ Institut d’Astrophysique de Paris, UMR7095 CNRS, Université Pierre & Marie Curie, 98 bis boulevard Arago, 75014 Paris, France
⁴ Institute of Physics, Laboratory of Astrophysics, Ecole Polytechnique Fédérale de Lausanne (EPFL), Observatoire de Sauverny, 1290 Versoix, Switzerland
⁵ Institut d’Estudis Espacials de Catalunya (IEEC), 08034 Barcelona, Spain
⁶ Institute of Space Sciences (ICE, CSIC), 08193 Barcelona, Spain
⁷ Department of Astrophysical Sciences, Princeton University, 4 Ivy Ln., Princeton 08544, USA
⁸ Department of Physics and Astronomy, University of Waterloo, Waterloo, ON N2L 3G1, Canada
⁹ Waterloo Centre for Astrophysics, Waterloo, ON N2L 3G1, Canada
¹⁰ Perimeter Institute for Theoretical Physics, 31 Caroline St. N., Waterloo, ON N2L 2Y5, Canada
¹¹ Argelander Institute for Astronomy, University of Bonn, Auf dem Hügel 71, 53121 Bonn, Germany
¹² NRC Herzberg Astronomy and Astrophysics, 5071 West Saanich Road, Victoria, BC V9E 2E7, Canada
¹³ Ruhr University Bochum, Faculty of Physics and Astronomy, Astronomical Institute (AIRUB), German Centre for Cosmological Lensing, 44780 Bochum, Germany
¹⁴ Department of Physics and Astronomy, University of British Columbia, 6224 Agricultural Road, Vancouver, V6T 1Z1 BC, Canada
¹⁵ Department of Physics, University of Oxford, Denys Wilkinson Building, Keble Road, Oxford OX1 3RH, UK
¹⁶ Canadian Astronomy Data Centre, Herzberg Astronomy and Astrophysics, National Research Council, 5071 West Saanich Rd, Victoria, BC V9E 2E7, Canada
¹⁷ Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB30HA, UK

Received: 21 July 2021
Accepted: 5 May 2022

Abstract

Context. The Ultraviolet Near-Infrared Optical Northern Survey (UNIONS) is an ongoing collaboration that will provide the largest deep photometric survey of the northern sky in four optical bands to date. As part of this collaboration, the Canada-France Imaging Survey (CFIS) is observing r-band data with an average seeing of 0.65 arcsec, which is complete to magnitude 24.5 and thus ideal for weak-lensing studies.

Aims. We perform the first weak-lensing analysis of CFIS r-band data over an area spanning 1700 deg² of the sky. We create a catalogue with measured shapes for 40 million galaxies, corresponding to an effective density of 6.8 galaxies per square arcminute, and demonstrate a low level of systematic biases. This work serves as the basis for further cosmological studies that will use the full UNIONS survey of 4800 deg² when completed.

Methods. Here we present SHAPEPIPE, a newly developed weak-lensing pipeline. This pipeline makes use of state-of-the-art methods such as NGMIX for accurate galaxy shape measurement. Shear calibration is performed with metacalibration. We carry out extensive validation tests on the point spread function (PSF) and on the galaxy shapes. In addition, we create realistic image simulations to validate the estimated shear.

Results. We quantify the PSF model accuracy and show that the level of systematics is low as measured by the PSF residuals. Their effect on the shear two-point correlation function is sub-dominant compared to the cosmological contribution on angular scales < 100′. The additive shear bias is below 5 × 10⁻⁴, and the residual multiplicative shear bias is at most 10⁻³ as measured on image simulations. Using complete orthogonal sets of E-/B-mode integrals (COSEBIs), we show that there are no significant B-modes present in second-order shear statistics. We present convergence maps and see clear correlations of the E-mode with known cluster positions. We measure the stacked tangential shear profile around Planck clusters at a significance higher than 4σ.