Euclid: Finding strong gravitational lenses in the Early Release Observations using convolutional neural networks
Abstract
The Early Release Observations (ERO) from Euclid have detected several new galaxy-galaxy strong gravitational lenses, with the all-sky survey expected to find 170,000 new systems, greatly enhancing studies of dark matter, dark energy, and constraints on the cosmological parameters. As a first step, visual inspection of all galaxies in one of the ERO fields (Perseus) was carried out to identify candidate strong lensing systems and compared to the predictions from Convolutional Neural Networks (CNNs). However, the entire ERO data set is too large for expert visual inspection. In this paper, we therefore extend the CNN analysis to the whole ERO data set, using different CNN architectures and methodologies. Using five CNN architectures, we identified 8,469 strong gravitational lens candidates from IE-band cutouts of 13 Euclid ERO fields, narrowing them to 97 through visual inspection, including 14 grade A and 31 grade B candidates. We present the spectroscopic confirmation of a strong gravitational lensing candidate, EUCLJ081705.61+702348.8. The foreground lensing galaxy, an early-type system at redshift z = 0.335, and the background source, a star-forming galaxy at redshift z = 1.475 with [O II] emission, are both identified. Lens modeling using the Euclid strong lens modeling pipeline reveals two distinct arcs in a lensing configuration, with an Einstein radius of 1.18 \pm 0.03 arcseconds, confirming the lensing nature of the system. These findings highlight the importance of a broad CNN search to efficiently reduce candidates, followed by visual inspection to eliminate false positives and achieve a high-purity sample of strong lenses in Euclid.
Keywords
Cite
@article{arxiv.2502.09802,
title = {Euclid: Finding strong gravitational lenses in the Early Release Observations using convolutional neural networks},
author = {B. C. Nagam and J. A. Acevedo Barroso and J. Wilde and I. T. Andika and A. Manjón-García and R. Pearce-Casey and D. Stern and J. W. Nightingale and L. A. Moustakas and K. McCarthy and E. Moravec and L. Leuzzi and K. Rojas and S. Serjeant and T. E. Collett and P. Matavulj and M. Walmsley and B. Clément and C. Tortora and R. Gavazzi and R. B. Metcalf and C. M. O'Riordan and G. Verdoes Kleijn and L. V. E. Koopmans and E. A. Valentijn and V. Busillo and S. Schuldt and F. Courbin and G. Vernardos and M. Meneghetti and A. Díaz-Sánchez and J. M. Diego and L. R. Ecker and T. T. Thai and A. R. Cooray and H. M. Courtois and L. Delchambre and G. Despali and D. Sluse and L. Ulivi and A. Melo and P. Corcho-Caballero and B. Altieri and A. Amara and S. Andreon and N. Auricchio and H. Aussel and C. Baccigalupi and M. Baldi and A. Balestra and S. Bardelli and P. Battaglia and D. Bonino and E. Branchini and M. Brescia and J. Brinchmann and A. Caillat and S. Camera and V. Capobianco and C. Carbone and J. Carretero and S. Casas and M. Castellano and G. Castignani and S. Cavuoti and A. Cimatti and C. Colodro-Conde and G. Congedo and C. J. Conselice and L. Conversi and Y. Copin and M. Cropper and A. Da Silva and H. Degaudenzi and G. De Lucia and A. M. Di Giorgio and J. Dinis and F. Dubath and C. A. J. Duncan and X. Dupac and S. Dusini and M. Fabricius and M. Farina and S. Farrens and S. Ferriol and M. Frailis and E. Franceschi and M. Fumana and K. George and W. Gillard and B. Gillis and C. Giocoli and P. Gómez-Alvarez and A. Grazian and F. Grupp and L. Guzzo and S. V. H. Haugan and J. Hoar and W. Holmes and I. Hook and F. Hormuth and A. Hornstrup and P. Hudelot and K. Jahnke and M. Jhabvala and B. Joachimi and E. Keihänen and S. Kermiche and B. Kubik and K. Kuijken and M. Kümmel and M. Kunz and H. Kurki-Suonio and R. Laureijs and D. Le Mignant and S. Ligori and P. B. Lilje and V. Lindholm and I. Lloro and G. Mainetti and E. Maiorano and O. Mansutti and O. Marggraf and K. Markovic and M. Martinelli and N. Martinet and F. Marulli and R. Massey and E. Medinaceli and M. Melchior and Y. Mellier and E. Merlin and G. Meylan and M. Moresco and L. Moscardini and R. Nakajima and C. Neissner and R. C. Nichol and S. -M. Niemi and C. Padilla and S. Paltani and F. Pasian and K. Pedersen and W. J. Percival and V. Pettorino and S. Pires and G. Polenta and M. Poncet and L. A. Popa and L. Pozzetti and F. Raison and R. Rebolo and A. Renzi and J. Rhodes and G. Riccio and E. Romelli and M. Roncarelli and E. Rossetti and R. Saglia and Z. Sakr and A. G. Sánchez and D. Sapone and B. Sartoris and M. Schirmer and P. Schneider and T. Schrabback and A. Secroun and G. Seidel and S. Serrano and C. Sirignano and G. Sirri and J. Skottfelt and L. Stanco and J. -L. Starck and J. Steinwagner and P. Tallada-Crespí and D. Tavagnacco and A. N. Taylor and H. I. Teplitz and I. Tereno and R. Toledo-Moreo and F. Torradeflot and A. Tsyganov and I. Tutusaus and L. Valenziano and T. Vassallo and A. Veropalumbo and Y. Wang and J. Weller and A. Zacchei and E. Zucca and C. Burigana and A. Mora and M. Pöntinen and V. Scottez},
journal= {arXiv preprint arXiv:2502.09802},
year = {2025}
}