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

Abstract

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, CFIS is taking $r$-band data with an average seeing of 0.65 arcsec, which is complete to magnitude 24.5 and thus ideal for weak-lensing studies. We perform the first weak-lensing analysis of CFIS $r$-band data over an area spanning 1700 deg${}^2$ 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 using the full UNIONS survey of 4800 deg${}^2$ when completed. 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. 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 arcmin. The additive shear bias is below 5x$10^{-4}$, and the residual multiplicative shear bias is at most $10^{-3}$ as measured on image simulations. Using 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 $4\sigma$.

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Cited by in corpus (14)

• The fifth data release of the Kilo Degree Survey: Multi-epoch optical/NIR imaging covering wide and legacy-calibration fields
• UNIONS: The impact of systematic errors on weak-lensing peak counts
• Forklens: Accurate weak-lensing shear measurement with deep learning
• The infall region as a complementary probe to cluster abundance
• UNIONS: a direct measurement of intrinsic alignment with BOSS/eBOSS spectroscopy
• Searching for strong lensing by late-type galaxies in UNIONS
• Impact of weak-lensing mass-mapping algorithms on cosmology inference
• Galaxies OBserved as Low-luminosity Identified Nebulae (GOBLIN): a catalog of 43,000 high-probability dwarf galaxy candidates in the UNIONS survey
• Cosmological parameters from the joint analysis of Density Split and Second Order Statistics: an Emulator based on the Halo Occupation Distribution
• Blending effects on shear measurement synergy between Euclid-like and LSST-like surveys
• Galaxy-Point Spread Function correlations as a probe of weak-lensing systematics with UNIONS data
• Constraining cosmological parameters using density split lensing and the conditional stellar mass function
• Emulating redshift mixing due to blending in weak gravitational lensing
• A Super-Eddington, Lensing-Magnified Quasar at $z=5.07$ observed with JWST