Euclid preparation. Refining input galaxy shape distributions for shear calibration simulations
Abstract
The Euclid Wide Survey (EWS) will cover the majority of the extragalactic sky with a resolution similar to the Hubble Space Telescope. This unprecedented data set will introduce a new era of precision cosmology. However, systematic effects need to be controlled better than ever. One of the sources of systematic uncertainties in weak gravitational lensing are biases introduced during the shear measurement. Determining these biases precisely allows the calibration of cosmological measurements to within Euclid's required accuracy. The simulations that are used to determine such biases, need to resemble the real observations. In this work, we aim to learn distributions of galaxy shape parameters from real Euclid data and use the new information to augment the morphological information in the Flagship galaxy mock catalogue. The morphology is extracted using single and double-S\'ersic model fits to the real data, for which we use SourceXtractor++. We train our pipeline on deep Euclid observations of a field with rich auxiliary data and then use it to simulate EWS-like data. In these simulations we compare the multiplicative bias between the morphology from the Flagship catalogue, the trained single-S\'ersic morphology, and the trained double-S\'ersic morphology. We find that the image simulations with the updated morphology result in a percent-level change in the multiplicative shear bias compared to the original morphology from Flagship. This bias exceeds Euclid's tight error budget by a factor of five and underlines the need for this work. Furthermore, we study the sensitivity of the multiplicative bias to key morphological parameters and show that our approach satisfies the requirements for the cosmology analysis with the first data release of Euclid.
Cite
@article{arxiv.2604.26684,
title = {Euclid preparation. Refining input galaxy shape distributions for shear calibration simulations},
author = {Euclid Collaboration and H. Jansen and N. Martinet and S. Grandis and H. Hoekstra and S. -S. Li and T. Schrabback and G. Congedo and B. Csizi and F. Kleinebreil and G. Mankar and N. Zimmermann and B. Altieri and S. Andreon and N. Auricchio and C. Baccigalupi and M. Baldi and S. Bardelli and P. Battaglia and A. Biviano and E. Branchini and M. Brescia and S. Camera and V. Capobianco and C. Carbone and V. F. Cardone and J. Carretero and S. Casas and F. J. Castander and M. Castellano and G. Castignani and S. Cavuoti and A. Cimatti and C. Colodro-Conde and L. Conversi and Y. Copin and F. Courbin and H. M. Courtois and M. Cropper and H. Degaudenzi and G. De Lucia and H. Dole and F. Dubath and X. Dupac and S. Escoffier and M. Farina and R. Farinelli and S. Farrens and S. Ferriol and P. Fosalba and S. Fotopoulou and N. Fourmanoit and M. Frailis and E. Franceschi and M. Fumana and S. Galeotta and K. George and B. Gillis and C. Giocoli and J. Gracia-Carpio and A. Grazian and F. Grupp and S. V. H. Haugan and W. Holmes and I. M. Hook and F. Hormuth and A. Hornstrup and K. Jahnke and M. Jhabvala and B. Joachimi and S. Kermiche and A. Kiessling and B. Kubik and K. Kuijken and M. Kümmel and M. Kunz and H. Kurki-Suonio and A. M. C. Le Brun and S. Ligori and P. B. Lilje and V. Lindholm and I. Lloro and G. Mainetti and O. Mansutti and O. Marggraf and M. Martinelli and F. Marulli and R. J. Massey and E. Medinaceli and M. Meneghetti and E. Merlin and G. Meylan and A. Mora and M. Moresco and B. Morin and L. Moscardini and R. Nakajima and C. Neissner and S. -M. Niemi and J. W. Nightingale 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 L. A. Popa and F. Raison and A. Renzi and J. Rhodes and G. Riccio and M. Roncarelli and R. Saglia and Z. Sakr and D. Sapone and P. Schneider and A. Secroun and E. Sihvola and P. Simon and C. Sirignano and G. Sirri and L. Stanco and P. Tallada-Crespí and A. N. Taylor and I. Tereno and N. Tessore and S. Toft and R. Toledo-Moreo and F. Torradeflot and I. Tutusaus and J. Valiviita and T. Vassallo and G. Verdoes Kleijn and Y. Wang and J. Weller and G. Zamorani and F. M. Zerbi and E. Zucca and M. Ballardini and A. Boucaud and E. Bozzo and C. Burigana and R. Cabanac and M. Calabrese and A. Cappi and T. Castro and J. A. Escartin Vigo and J. García-Bellido and S. Hemmati and E. Jullo and J. Macias-Perez and R. Maoli and J. Martín-Fleitas and N. Mauri and R. B. Metcalf and P. Monaco and A. Pezzotta and M. Pöntinen and I. Risso and V. Scottez and M. Sereno and M. Tenti and M. Tucci and M. Viel and M. Wiesmann and Y. Akrami and I. T. Andika and G. Angora and S. Anselmi and M. Archidiacono and F. Atrio-Barandela and L. Baumont and L. Bazzanini and D. Bertacca and M. Bethermin and F. Beutler and A. Blanchard and L. Blot and M. Bonici and S. Borgani and M. L. Brown and S. Bruton and A. Calabro and B. Camacho Quevedo and F. Caro and C. S. Carvalho and F. Cogato and A. R. Cooray and O. Cucciati and J. E. Davies and T. de Boer and G. Desprez and A. Díaz-Sánchez and S. Di Domizio and J. M. Diego and V. Duret and M. Y. Elkhashab and Y. Fang and A. Finoguenov and A. Franco and K. Ganga and R. Gavazzi and E. Gaztanaga and F. Giacomini and F. Gianotti and G. Gozaliasl and A. Gruppuso and M. Guidi and C. M. Gutierrez and A. Hall and C. Hernández-Monteagudo and H. Hildebrandt and J. J. E. Kajava and Y. Kang and V. Kansal and D. Karagiannis and K. Kiiveri and J. Kim and C. C. Kirkpatrick and K. Koyama and S. Kruk and M. C. Lam and M. Lattanzi and L. Legrand and M. Lembo and F. Lepori and G. Leroy and G. F. Lesci and J. Lesgourgues and T. I. Liaudat and S. J. Liu and M. Magliocchetti and F. Mannucci and C. J. A. P. Martins and L. Maurin and M. Miluzio and C. Moretti and G. Morgante and S. Nadathur and K. Naidoo and A. Navarro-Alsina and S. Nesseris and F. Pace and D. Paoletti and F. Passalacqua and K. Paterson and L. Patrizii and C. Pattison and A. Pisani and D. Potter and G. W. Pratt and S. Quai and M. Radovich and K. Rojas and W. Roster and S. Sacquegna and M. Sahlén and D. B. Sanders and E. Sarpa and A. Schneider and D. Sciotti and D. Scognamiglio and E. Sellentin and L. C. Smith and E. Soubrie and I. Szapudi and K. Tanidis and F. Tarsitano and G. Testera and M. Tewes and R. Teyssier and S. Tosi and A. Troja and C. Uhlemann and C. Valieri and A. Venhola and D. Vergani and G. Verza and E. Vilenius and S. Vinciguerra and M. von Wietersheim-Kramsta and N. A. Walton and A. H. Wright},
journal= {arXiv preprint arXiv:2604.26684},
year = {2026}
}
Comments
This paper is published on behalf of the Euclid Consortium. 24 pages, 25 figures, 6 tables. Submitted to A&A