UNIONS: The impact of systematic errors on weaklensing peak counts
Abstract
Context. The Ultraviolet NearInfrared Optical Northern Survey (UNIONS) is an ongoing deep photometric multiband survey of the northern sky. As part of UNIONS, the CanadaFrance Imaging Survey (CFIS) provides rband data, which we use to study weaklensing peak counts for cosmological inference.
Aims: We assess systematic effects for weaklensing peak counts and their impact on cosmological parameters for the UNIONS survey. In particular, we present results on local calibration, metacalibration shear bias, baryonic feedback, the source galaxy redshift estimate, intrinsic alignment, and cluster member dilution.
Methods: For each uncertainty and systematic effect, we describe our mitigation scheme and the impact on cosmological parameter constraints. We obtain constraints on cosmological parameters from Monte Carlo Markov chains using CFIS data and MassiveNuS Nbody simulations as a model for peak counts statistics.
Results: Depending on the calibration (local versus global, and the inclusion or not of the residual multiplicative shear bias), the mean matter density parameter, Ω_{m}, can shift by up to −0.024 (−0.5σ). We also see that including baryonic corrections can shift Ω_{m} by +0.027 (+0.5σ) with respect to the darkmatteronly simulations. Reducing the impact of the intrinsic alignment and cluster member dilution through signaltonoise cuts leads to larger constraints. Finally, with a mean redshift uncertainty of Δz̄ = 0.03, we see that the shift in Ω_{m} (+0.001, which corresponds to +0.02σ) is not significant.
Conclusions: This paper investigates, for the first time with UNIONS weaklensing data and peak counts, the impact of systematic effects. The value of Ω_{m} is the most impacted and can shift by up to ∼0.03, which corresponds to 0.5σ depending on the choices for each systematics. We expect constraints to become more reliable with future (larger) data catalogs, for which the current pipeline will provide a starting point. The code used to obtain the results is available on GitHub.
 Publication:

Astronomy and Astrophysics
 Pub Date:
 March 2023
 DOI:
 10.1051/00046361/202243899
 arXiv:
 arXiv:2204.06280
 Bibcode:
 2023A&A...671A..17A
 Keywords:

 largescale structure of Universe;
 gravitational lensing: weak;
 methods: data analysis;
 Astrophysics  Cosmology and Nongalactic Astrophysics
 EPrint:
 19 pages, 19 figures