Strong lensing in UNIONS: Toward a pipeline from discovery to modeling

Abstract

We present a search for galaxy-scale strong gravitational lenses in the initial 2 500 square degrees of the Canada-France Imaging Survey (CFIS). We designed a convolutional neural network (CNN) committee that we applied to a selection of 2 344 002 exquisite-seeing $r$-band images of color-selected luminous red galaxies (LRGs). Our classification uses a realistic training set where the lensing galaxies and the lensed sources are both taken from real data, namely the CFIS $r$-band images themselves and the Hubble Space Telescope (HST). A total of 9 460 candidates obtain a score above 0.5 with the CNN committee. After a visual inspection of the candidates, we find a total of 133 lens candidates, of which 104 are completely new. The set of false positives mainly contains ring, spiral, and merger galaxies, and to a lesser extent galaxies with nearby companions. We classify 32 of the lens candidates as secure lenses and 101 as maybe lenses. For the 32 highest quality lenses, we also fit a singular isothermal ellipsoid mass profile with external shear along with an elliptical Sersic profile for the lens and source light. This automated modeling step provides distributions of properties for both sources and lenses that have Einstein radii in the range $0.5\arcsec<θ_E<2.5\arcsec$. Finally, we introduce a new lens and/or source single-band deblending algorithm based on auto-encoder representation of our candidates. This is the first time an end-to-end lens-finding and modeling pipeline is assembled together, in view of future lens searches in a single band, as will be possible with Euclid.

29 pages, 21 figures, accepted by A&A, in press

References in corpus (26)

• Wide-Field InfrarRed Survey Telescope-Astrophysics Focused Telescope Assets WFIRST-AFTA 2015 Report
• Delving Deep into Rectifiers: Surpassing Human-Level Performance on ImageNet Classification
• zCOSMOS: A Large VLT/VIMOS redshift survey covering 0 < z < 3 in the COSMOS field
• H0LiCOW V. New COSMOGRAIL time delays of HE0435-1223: $H_0$ to 3.8% precision from strong lensing in a flat $\Lambda$CDM model
• The Sloan Lens ACS Survey. V. The Full ACS Strong-Lens Sample
• The VIMOS Ultra-Deep Survey: ~10,000 galaxies with spectroscopic redshifts to study galaxy assembly at early epochs 2<z<~6
• The fourth data release of the Kilo-Degree Survey: ugri imaging and nine-band optical-IR photometry over 1000 square degrees
• Bayesian Strong Gravitational-Lens Modeling on Adaptive Grids: Objective Detection of Mass Substructure in Galaxies
• MegaPipe: the MegaCam image stacking pipeline at the Canadian Astronomical Data Centre
• Inference of the Cold Dark Matter substructure mass function at z=0.2 using strong gravitational lenses
• The Halos of Satellite Galaxies: the Companion of the Massive Elliptical Lens SL2S J08544-0121
• The CFHTLS Strong Lensing Legacy Survey: I. Survey overview and T0002 release sample
• The Sloan Digital Sky Survey Quasar Lens Search. I. Candidate Selection Algorithm
• The SL2S Galaxy-scale Lens Sample. V. Dark Matter Halos and Stellar IMF of Massive Early-type Galaxies out to Redshift 0.8
• First catalog of strong lens candidates in the COSMOS field
• The Herschel-ATLAS: a sample of 500μm-selected lensed galaxies over 600 square degrees
• The Sloan Lens ACS Survey. XII. Extending Strong Lensing to Lower Masses
• The Canada-France Imaging Survey: First results from the u-band component
• Galaxy Zoo: Morphological Classifications for 120,000 Galaxies in HST Legacy Imaging
• The 0.1<z<1.65 evolution of the bright end of the [OII] luminosity function
• The Canada-France Imaging Survey: Reconstructing the Milky Way Star Formation History from its White Dwarf Population
• CHITAH: Strong-gravitational-lens hunter in imaging surveys
• The inner mass power spectrum of galaxies using strong gravitational lensing: beyond linear approximation
• Five New High-Redshift Quasar Lenses from the Sloan Digital Sky Survey
• Strong lensing in UNIONS: Toward a pipeline from discovery to modeling
• Zooming into the Cosmic Horseshoe: new insights on the lens profile and the source shape

Cited by in corpus (21)

• Strong gravitational lensing and microlensing of supernovae
• Strong lensing in UNIONS: Toward a pipeline from discovery to modeling
• TDCOSMO X. Automated Modeling of 9 Strongly Lensed Quasars and Comparison Between Lens Modeling Software
• Strong Lensing by Galaxies
• Strong lensing selection effects
• New Strong Gravitational Lenses from the DESI Legacy Imaging Surveys Data Release 9
• Euclid: The Early Release Observations Lens Search Experiment
• The impact of human expert visual inspection on the discovery of strong gravitational lenses
• The COSMOS-Web ring: in-depth characterization of an Einstein ring lensing system at z~2
• HOLISMOKES -- IX. Neural network inference of strong-lens parameters and uncertainties from ground-based images
• HOLISMOKES -- X. Comparison between neural network and semi-automated traditional modeling of strong lenses
• Euclid Preparation XXXIII. Characterization of convolutional neural networks for the identification of galaxy-galaxy strong lensing events
• A Bayesian Approach to Strong Lens Finding in the Era of Wide-area Surveys
• HOLISMOKES XIII: Strong-lens candidates at all mass scales and their environments from the Hyper-Suprime Cam and deep learning
• DeepGraviLens: a Multi-Modal Architecture for Classifying Gravitational Lensing Data
• Measuring the Substructure Mass Power Spectrum of 23 SLACS Strong Galaxy-Galaxy Lenses with Convolutional Neural Networks
• The revolution in strong lensing discoveries from Euclid
• HOLISMOKES XVI: Lens search in HSC-PDR3 with a neural network committee and post-processing for false-positive removal
• Searching for strong lensing by late-type galaxies in UNIONS
• Accelerating lensed quasar discovery and modeling with physics-informed variational autoencoders
• Galaxies OBserved as Low-luminosity Identified Nebulae (GOBLIN): a catalog of 43,000 high-probability dwarf galaxy candidates in the UNIONS survey