EasyCritics I: Efficient detection of strongly-lensing galaxy groups and clusters in wide-field surveys

Abstract

We present EasyCritics, an algorithm to detect strongly-lensing groups and clusters in wide-field surveys without relying on a direct recognition of arcs. EasyCritics assumes that light traces mass in order to predict the most likely locations of critical curves from the observed fluxes of luminous red early-type galaxies in the line of sight. The positions, redshifts and fluxes of these galaxies constrain the idealized gravitational lensing potential as a function of source redshift up to five free parameters, which are calibrated on few known lenses. From the lensing potential, EasyCritics derives the critical curves for a given, representative source redshift. The code is highly parallelized, uses fast Fourier methods and, optionally, GPU acceleration in order to process large datasets efficiently. The search of a $1{\mathrm{deg}}^2$ field of view requires less than 1 minute on a modern quad-core CPU, when using a pixel resolution of $0.25^{\prime \prime }/\mathrm{px}$. In this first part of a paper series on EasyCritics, we describe the main underlying concepts and present a first demonstration on data from the Canada-France-Hawaii-Telescope Lensing Survey. We show that EasyCritics is able to identify known group- and cluster-scale lenses, including a cluster with two giant arc candidates that were previously missed by automated arc detectors.

18 pages, 12 figures, submitted to MNRAS, added minor revisions

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• AMICO galaxy clusters in KiDS-DR3: sample properties and selection function
• Testing Convolutional Neural Networks for finding strong gravitational lenses in KiDS
• On building a cluster watch-list for identifying strongly lensed supernovae, gravitational waves and kilonovae
• Generalised model-independent characterisation of strong gravitational lenses IV: formalism-intrinsic degeneracies
• Image simulations for gravitational lensing with SkyLens
• AMICO-COSMOS galaxy cluster and group catalogue up to $z=2$: Sample properties and X-ray counterparts
• MIFAL: fully automated Multiple-Image Finder ALgorithm for strong-lens modelling -- proof of concept
• AStroLens: Automatic Strong-Lens Modeling of X-ray Selected Galaxy Clusters
• Enabling discovery of gravitationally lensed explosive transients: a new method to build an all-sky watch-list of groups and clusters of galaxies
• A Strong-Lensing Model for the WMDF JWST/GTO Very Rich Cluster Abell 1489
• EasyCritics II. Testing its efficiency: new gravitational lens candidates in CFHTLenS
• A compact group lens modeled with GIGA-Lens: Enhanced inference for complex systems
• COOL-LAMPS. VII. Quantifying Strong-lens Scaling Relations with 177 Cluster-scale Strong Gravitational Lenses in DECaLS