UNIONS: The impact of systematic errors on weaklensing peak counts
Abstract
UNIONS is an ongoing deep photometric multiband survey of the Northern sky. As part of UNIONS, CFIS provides rband data which we use to study weaklensing peak counts for cosmological inference. 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 the cluster member dilution. 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 MCMC using CFIS data and MassiveNuS Nbody simulations as a model for peak counts statistics. Depending on the calibration (local versus global, and the inclusion of the residual multiplicative shear bias), the mean matter density parameter $\Omega_m$ can shift up to $0.024$ ($0.5\sigma$). We also see that including baryonic corrections can shift $\Omega_m$ by $+0.027$ ($+0.5 \sigma$) with respect to the DMonly simulations. Reducing the impact of the intrinsic alignment and cluster member dilution through signaltonoise cuts can lead to a shift in $\Omega_m$ of $+0.027$ ($+0.5 \sigma$). Finally, with a mean redshift uncertainty of $\Delta \bar{z} = 0.03$, we see that the shift of $\Omega_m$ ($+0.001$ which corresponds to $+0.02 \sigma$) is not significant. This paper investigates for the first time with UNIONS weaklensing data and peak counts the impact of systematic effects. The value of $\Omega_m$ is the most impacted and can shift up to $\sim 0.03$ which corresponds to $0.5\sigma$ depending on the choices for each systematics. We expect constraints to become more reliable with future (larger) data catalogues, for which the current pipeline will provide a starting point.
 Publication:

arXiv eprints
 Pub Date:
 April 2022
 arXiv:
 arXiv:2204.06280
 Bibcode:
 2022arXiv220406280A
 Keywords:

 Astrophysics  Cosmology and Nongalactic Astrophysics
 EPrint:
 17 pages, 17 figures